JP4656706B2 - Imaging device and focal length conversion device - Google Patents

Description

【００２８】
ただし、ａは被写体距離、ｂは結像距離、ｆはレンズの焦点距離、δは錯乱円径、Ｆはレンズの口径比（Ｆナンバー）、ｄは、デフォーカス量＝撮像面（予定焦平面）と結像面（合焦平面）とのずれ距離であり、結像面がレンズ（被写体）側にずれた場合を正、逆を負とした。
【００２９】
式（１）は「結像公式」と呼ばれているものである。ただし、いわゆる「光学」では一般に被写体側への距離を負と考えるが、本例においては実距離を正としている。
【００３０】
式（２）において錯乱円とは、被写体の１点から発せられて、合焦平面においては１点に結像するはずの光が、撮像面がずれたために円盤状に広がったものを称し、その直径が錯乱円径である。すなわちこの錯乱円は、ピントずれによって生じるぼけの定量的表現である。
【００３１】
ここで、図２および図３を用いて、式（１），式（２）の意味について説明する。
図２のように、被写体距離ａに有る光軸から高さｘの被写体アイが結像距離ｂにて合焦して高さｙの倒立像ウエを生じたとする。光軸に平行な光線は焦点カ、キを通るから、△イキアと△クキケおよび△エカウと△オカケのそれぞれの相似関係から
ｘ／（ａ−ｆ）＝ ｙ／ｆ
ｙ／（ｂ−ｆ）＝ ｘ／ｆ
が求まる。この２つの式から比 ｙ／ｘ を消去すれば結像公式（１）が得られる。
なお比ｙ／ｘは結像倍率であり、記号ｍで表わされることが多い。上式を変形すれば、
倍率 ｍ ＝ ｆ／（ａ−ｆ）＝ ｂ／ａ
であることも容易に示せる。
【００３２】
図３のように、撮像面における錯乱円の大きさはレンズの口径Ａに依存する。
▲１▼結像距離が撮像面距離ｂよりも小さい場合（実合焦点がツの場合）と▲２▼大きい場合（同ツ’の場合）で２通りの場合が生じる。▲１▼△タチツと△テトツまたは▲２▼△タチツ’と△テトツ’の相似関係から、
▲１▼Ａ／（ｂ−ｄ）＝δ／ｄ または ▲２▼Ａ／（ｂ＋ｄ）＝δ／ｄ
となるが、ｄの符号について、▲１▼の場合を基準にして正、▲２▼の場合は負として扱うことにより、いずれの場合も共通の一つの関係式
Ａ／（ｂ−ｄ）＝δ／|ｄ|
とすることができる。この式とＦ値の定義 Ｆ＝ｆ／Ａ を用いて上述の錯乱円径の式（２）が得られる。
【００３３】
ここで、距離ａにおける主要被写体にピントを合わせて撮像する場合の、前後の被写体に対して生じるぼけ＝錯乱円径を考える。距離ａに対して距離Δａだけ後ろにずれた被写体（前にずれた被写体はΔａが負の場合として含む）の合焦面は、撮像面（これは主要被写体の合焦面に等しい）に対してレンズに近い側にずれて結像するから、ずれ量をΔｂとして上記式（１）、（２）に適用すれば、
【００３４】
【数２】

【００３５】
式（３）をΔｂについて解き直して式（４）に代入することよりΔｂを消去して、
【００３６】
【数３】

【００３７】
を得る。ここで、距離ずれΔａを被写体（撮影対象空間）の奥行きを表わすパラメータであると考え、改めて記号Ｄに書き直し、さらに画面サイズｗで割って規格化したものを考える。
【００３８】
【数４】

【００３９】
画面サイズｗによる規格化は、「画面サイズが異なる撮像系においては、物理的に同じ大きさのぼけでも画像において生じる相対的なぼけの大きさが異なる」ため、これを同じ評価尺度で評価するためのものである。判り易く言えば、全画面を同じ大きさの画面に引き伸ばし（同じ大きさのディスプレイにフル画面で表示し）たときのぼけの大きさに相当している。
【００４０】
ｗを撮像画面の対角線長とし、銀塩３５ｍｍ（ライカフレーム）サイズカメラにおける被写界深度計算のための伝統的な許容錯乱円サイズ３３．３μｍを考えた時、δ／ｗ＝１／１３００であるからこれを基準とすると考え易いので、（６）式の１３００倍すなわち
【００４１】
【数５】

【００４２】
を奥行ぼけ関数（Depth Out-focus Function）と名付ける。
【００４３】
すなわち、奥行ぼけ関数ＤＯＦは、合焦している被写体面に対して奥行Ｄだけずれた被写体がどの程度ぼけるかを表わす関数であり、値１のとき、伝統的に用いられている許容錯乱円サイズ（ライカフレームカメラにおける３３．３μｍ相当）となる。なお、実用上の被写界深度から写真を見た時、大体ピントが合っているように感じられる範囲については写真の引き延ばし倍率にもよるが、多くの場合これの２倍程度以内、さらに大ぼけと感じるのは４〜５倍程度以上である。
なお、式（７）は近似を含まない厳密解であるが、超マクロ撮影の場合を除けば最後の項は＝１であるから通常の場合は次の近似式（７）’を用いても良い。
【００４４】
【数６】

【００４５】
以下では説明を明快にするため、結論に影響が無い場合は、近似式（７）’を用いる。なお図５乃至図８に示す例示グラフの数値計算は厳密式（７）を用いている。また、（７）、（７）’における係数項
【００４６】
【数７】

【００４７】
を、奥行きぼけ係数 DOC（Depth Out-focus Coefficient）と名付ける。DOFの式は、撮影距離ａが与えられた場合の奥行きぼけの関数形状（対変数Ｄ）は同じで、その値は奥行きぼけ係数DOCに比例する（DOCは図５乃至図８のDOFグラフの縦軸方向のスケーリングファクタとなっている）ことを示すものである。
【００４８】
ここで、撮像サイズｗが異なる系について、画角を等しく保つ条件として、画面サイズに比例した焦点距離が用いられることを考慮し、
画角係数 vc ≡ ｗ／ｆ を定義する。画角係数の意味を理解し易くするため、各画面サイズｗについてその焦点距離ｆと画角係数 vc との関係を図４に示す。例えば、ライカフレームサイズでｆ＝５０ｍｍの場合は画角係数 vc ＝０．８７となるが、２／３サイズでこれと等画角の撮像画像を得るための焦点距離はｆ＝１２．７ｍｍとなり、１／２サイズではｆ＝９．２ｍｍとなる。また、ライカフレームサイズでｆ＝１００ｍｍの場合は画角係数 vc ＝０．４３となるが、２／３サイズでこれと等画角の撮像画像を得るための焦点距離はｆ＝２５．４ｍｍとなり、１／２サイズではｆ＝１８．５ｍｍとなる。
【００４９】
今、等画角条件を適用するためｆ＝ｗ／vcを式（７）’に代入して
【００５０】
【数８】

【００５１】
を得る。奥行きぼけ係数 DOC ＝（１／F）・（ｗ／vc^２）と表現しても良い。
【００５２】
等画角条件で撮影する限りｖｃは定数、また同じ構図で撮影する時は被写体距離ａも同じだから、等Ｆ値で撮影する限り、奥行きぼけ係数 DOC（従って奥行ぼけ関数DOF(Ｄ) ）はｗに比例することが判る。このためデジタルカメラで撮影した画像は、銀塩カメラのものよりもぼけが小さくなるのである。例えば２／３サイズ（対角長１１ｍｍ）の場合はｗがライカフレームのほぼ１／４なので、ぼけも１／４しか生じない。
【００５３】
また、この（８）式から、ｗ／Ｆが変わらなければDOF(Ｄ)は変わらないこと、従って画面サイズが小さい分だけ絞りを開くことが出来れば、（近似項の微差を別にして）同一の奥行ぼけ特性を得ることができることも判る。
【００５４】
２．DOFの例示
図５、図６はそれぞれ付記した条件で撮像した場合の奥行ぼけ関数を示したものである。ぼけが画面サイズに比例していること、その結果として、画面サイズが小さくなると深度が深くなること、特に図５のｆ＝５０ｍｍ相当画角では、ライカフレームではまだかなり深度が浅いのに対して、２／３サイズや１／２サイズではほとんどパンフォーカス状態に近いという極端な結果の相違が生じてしまうこと等が読取れる。
【００５５】
３． 等Ｆ時の等価ぼけ撮像条件
このような現実に鑑みて、例えば等Ｆ値においても同じＤＯＦを得る方法を考える。残念ながら、式（８）を見れば、少なくとも等画角条件vc ＝ｃｏｎｓｔを守る限りこれは不可能である。そこで等画角でなくても良いことにすれば、式（８）において
ｗ／vc^２ ＝ｃｏｎｓｔ
とすれば良いことが判る。従って、画角係数ｖｃを画面サイズｗの平方根に比例した値に設定すれば良いことになる。これは例えば、画面サイズがリファレンスの１／４倍の場合は画角係数を（１／４）^１／２ ＝ １／２倍、従って相当（等画角換算）焦点距離は２倍にすれば良いことを意味する。（実焦点距離ｆは、
ｆ^２／ｗ ＝ ｗ／vc^２ ＝ｃｏｎｓｔから、（１／４）^１／２ ＝ １／２倍となる。）
これを一般式で表すと、ｆ１を想定撮像系の焦点距離、ｆ２をレンズ系１０１の焦点距離、ｗ１を想定撮像系の撮像画面サイズ、ｗ２をＣＣＤ撮像素子１０５の撮像画面サイズとした場合、等奥行ぼけ条件は、
ｆ１^２／ｗ１＝ｆ２^２／ｗ２
となる。
【００５６】
図７および図８は、図５、図６に対して同絞り条件の下で、焦点距離（画角係数）を１／２にした場合の２／３サイズの奥行ぼけ特性を示したものである。当然ながら、図５、図６のライカフレームと同じ特性が得られている。すなわち、画面全体を同じ写真サイズ（ディスプレイサイズ）に表示したときに観察者が見る奥行きぼけ特性は、リファレンスである銀塩カメラ（ライカフレーム撮像）の場合と完全に同一になると言える。ただしこの場合等画角条件を崩して、狭い画角範囲を撮像しているから、同一の画像が得られる訳では無いことに注意されたい。
次に、本実施形態の具体的な動作制御について説明する。以下では、リファレンスとなる想定撮像系としてライカフレームカメラを使用し、またＣＣＤ撮像素子１０５として２／３インチサイズのものを使用する場合を考える。
【００５７】
（第１の例）
まず、図９のフローチャートを参照して、焦点距離の換算制御を用いた第１の動作例について説明する。
まず、システムコントローラ１１２の制御の下、撮影者による操作スイッチ１１３の操作により想定撮像系の焦点距離ｆ１の値（例えばｆ１＝５０ｍｍ）が入力される（ステップＳ１１）。この焦点距離ｆ１の値は焦点距離換算部１１２ａに送られる。焦点距離換算部１１２ａでは、ｗ１とｗ２の撮像画面サイズ比に従って、等奥行ぼけ特性を得ることが可能なｆ２の値を算出するための換算処理が行われる（ステップＳ１２）。この場合、撮像画面サイズ比＝１／４だから焦点距離比１／２（ｆ２＝ｆ１×１／２）としてｆ２＝２５ｍｍを得る（参考：等画角条件の場合は焦点距離比１／２（ｆ２＝ｆ１×１／２＝１２．５ｍｍ））。
【００５８】
レンズ系１０１の焦点距離（撮像画角）をマニュアル調整する構成またはモードである場合には、焦点距離換算部１１２ａによって求められたｆ２の値がシステムコントローラ１１２によって操作表示系１１４やＬＣＤ１１１などに画面表示される（ステップＳ１３）。撮影者がレンズ系１０１の焦点距離（撮像画角）をｆ２に合わせた後に撮像を行うと、画角的にはライカフレームカメラより狭くなるが、奥行ぼけ特性（深度）についてはライカフレームカメラ５０ｍｍとほぼ等価な画像が得られる。
【００５９】
また、レンズ系１０１の焦点距離（撮像画角）をズーム駆動によって自動調整する構成またはモードである場合には、システムコントローラ１１２は、レンズドライバ１１５およびレンズ駆動回路１０２を用いてレンズ系１０１をズーム駆動することにより、レンズ系１０１の焦点距離を焦点距離換算部１１２ａによって求められたｆ２に自動設定する（ステップＳ１４）。この場合でも、奥行ぼけ特性（深度）はライカフレームカメラ５０ｍｍとほぼ等価な画像が得られる。
【００６０】
（第２の例）
次に、図１０のフローチャートを参照して、焦点距離の換算制御を用いた第２の動作例について説明する。
本例は、自動又は手動で設定されている現在のレンズ系１０１の焦点距離を検出し、その設定で得られる撮影画像の奥行ぼけ特性が、ライカフレームカメラにおけるどの焦点距離に対応するものであるかを撮影者に提示するものである。すなわち、まず、撮影時においては、撮影者による数値指定や、手動を含めた公知のＴ←→Ｗ駆動などによって、レンズ系１０１の焦点距離が所定の値に設定される（ステップＳ２１）。システムコントローラ１１２は、このようにして自動又は手動で設定されている撮像レンズ系１０１の現在の焦点距離ｆ２の設定値を認識する（ステップＳ２２）。数値指定でズーム駆動する場合には、撮影者によって入力または指定された数値が現在の焦点距離ｆ２として認識され、また手動を含めたＴ←→Ｗ駆動等の場合には、レンズ駆動回路１０２やレンズドライバ１１５などに設けられる公知のズームエンコーダ等にて現在のズーム値が検出され、それが焦点距離ｆ２として認識されることになる。なお、レンズ系１０１のズーム機構としては、多段切り換え型のものであってもよい。これは上述の第１の例の場合も同じである。
【００６１】
次いで、システムコントローラ１１２は、焦点距離換算部１１２ａを用いて、現在の焦点距離ｆ２に対応するｆ１の値を求め（ステップＳ２３）、それを操作表示系１１４やＬＣＤ１１１などに画面表示する（ステップＳ２４）。この場合、現在のｆ２の２倍の数値がｆ１として表示されることになる。これによって、ライカフレームカメラでどの焦点距離を用いたときのぼけ特性と同じかが容易に判る。
【００６２】
次に、デジタルカメラではなく単体の焦点距離換算装置として実現した場合の動作を、第３および第４の例として説明する。この場合、焦点距離換算装置は、図１の構成から撮像系および記録系などを除外した残りの部位、すなわち入力機構としての操作スイッチ系１１３、表示機構としての操作表示系１１４、およびシステムコントローラ１１２のみで構成することができる。
【００６３】
（第３の例）
まず、操作者による操作スイッチ系１１３の操作により、想定撮像系の撮像画面サイズｗ１、使用撮像系の撮像画面サイズｗ２、および想定撮像系の焦点距離ｆ１の値が入力される（ステップＳ３１）。これら入力値は焦点距離換算部１１２ａに送られる。焦点距離換算部１１２ａでは、ｗ１とｗ２の撮像画面サイズ比に従って、等奥行ぼけ特性を得ることが可能なｆ２の値を算出するための換算処理が行われ（ステップＳ３２）、これによって求められたｆ２の値が操作表示系１１４に表示される（ステップＳ３３）。想定撮像系の撮像画面サイズｗ１としてはライカフレームの画面サイズがデフォルト値として記憶されており、ｗ１が入力されない場合には、ライカフレームの画面サイズ＝ｗ１とした換算が行われる。
【００６４】
（第４の例）
本例は、第３の例とは逆に、使用撮像系の焦点距離ｆ２が、想定撮像系でどの焦点距離を用いたときのぼけ特性と同じかを換算する例である。まず、操作者による操作スイッチ系１１３の操作により、想定撮像系の撮像画面サイズｗ１、使用撮像系の撮像画面サイズｗ２、および使用撮像系の焦点距離ｆ２の値が入力される（ステップＳ３４）。これら入力値は焦点距離換算部１１２ａに送られる。焦点距離換算部１１２ａでは、ｗ１とｗ２の撮像画面サイズ比に従って、ｆ２と等奥行ぼけ特性となるｆ１の値を算出するための換算処理が行われ（ステップＳ３５）、これによって求められたｆ１の値が操作表示系１１４に表示される（ステップＳ３６）。なお、第３の例の場合と同様、想定撮像系の撮像画面サイズｗ１としてはライカフレームの画面サイズがデフォルト値として記憶されており、ｗ１が入力されない場合には、ライカフレームの画面サイズ＝ｗ１とした換算が行われる。
【００６５】
なお、本発明は上述した実施形態に限定されるものではない。本実施形態では、想定撮像系を３５ミリ版銀塩フィルムカメラ、また実施形態カメラをデジタルカメラとしたが、上記においてはただ画面サイズの違いのみに基づく考察、処理しか条件にしてないから、本発明の焦点距離の換算処理は、銀塩フィルムと電子撮像系などの方式を問わず、画面サイズが異なる場合のＦ値が等しい条件下における等奥行きぼけ撮影一般に適用可能であることは明らかである。また実施形態では撮像画面サイズｗとして画面の対角長を用いたが、画面アスペクト比（横縦比）が等しい（すなわち画面形状が相似の）撮像系間の換算に際してはもちろんのこと、アスペクト比が異なる撮像系間の換算に際しても、対角長に限らず、水平長（画面巾）、垂直長（画面高）など画面の大きさを代表する任意の１次元量を画面サイズｗとして用いて良い。また、スチルカメラ、ムービーカメラの別を問わず適用することができる。
【００６６】
また、本発明は、実施段階ではその要旨を逸脱しない範囲で種々に変形することが可能である。更に、上記実施形態には種々の段階の発明が含まれており、開示される複数の構成要件における適宜な組み合わせにより種々の発明が抽出され得る。例えば、実施形態に示される全構成要件から幾つかの構成要件が削除されても、発明が解決しようとする課題の欄で述べた課題が解決でき、発明の効果の欄で述べられている効果が得られる場合には、この構成要件が削除された構成が発明として抽出され得る。
【００６７】
【発明の効果】
以上詳述したように本発明によれば、現実の被写体を所定の撮像系（例えば銀塩カメラ）で撮影した時と同等のぼけ特性を有した撮像を実現することが可能となる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係わる電子カメラの概略構成を示すブロック図。
【図２】同実施形態に適用される撮像光学系の撮像公式を説明するための図。
【図３】同実施形態に適用される撮像光学系の錯乱円の大きさとデフォーカス量との関係を示す図。
【図４】同実施形態に適用される撮像光学系と想定撮像系それぞれにおける焦点距離と画角係数との関係を示す図。
【図５】同実施形態に適用される撮像光学系と想定撮像系それぞれにおける奥行ぼけ特性を示す第１の図。
【図６】同実施形態に適用される撮像光学系と想定撮像系それぞれにおける奥行ぼけ特性を示す第２の図。
【図７】同実施形態に適用される撮像光学系と想定撮像系それぞれにおける奥行ぼけ特性を示す第３の図。
【図８】同実施形態に適用される撮像光学系と想定撮像系それぞれにおける奥行ぼけ特性を示す第４の図。
【図９】同実施形態の第１の動作例を示すフローチャート。
【図１０】同実施形態の第２の動作例を示すフローチャート。
【図１１】同実施形態の第３の動作例を示すフローチャート。
【図１２】同実施形態の第３の動作例を示すフローチャート。
【符号の説明】
１０１…レンズ系
１０２…レンズ駆動機構
１０３…露出制御機構
１０４…フィルタ
１０５…ＣＣＤカラー撮像素子
１０６…ＣＣＤドライバ
１０７…プリプロセス部
１０８…デジタルプロセス部
１０９…カードインターフェース
１１０…メモリカード
１１１…ＬＣＤ画像表示系
１１２…システムコントローラ（ＣＰＵ）
１１３…操作スイッチ系
１１４…操作表示系
１１５…レンズドライバ
１１６…ストロボ
１１７…露出制御ドライバ
１１８…不揮発性メモリ（ＥＥＰＲＯＭ）
１１２ａ…焦点距離換算部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus and a focal length conversion apparatus related to the imaging optical system, and more particularly to an imaging apparatus and a focal length conversion apparatus having an image blurring function.
[0002]
[Prior art]
Imaging devices such as video cameras have been widely used in the past, and electronic still cameras that mainly capture and record still images have recently become widespread as digital cameras.
[0003]
By the way, the image area of the image sensor used by the electronic imaging device is not only Leica (double frame), which is a typical frame format of silver halide film, but also half size (single frame) or APS (Advanced Photo System). Is usually very small. This is an inevitable situation arising from a demand for improving the semiconductor manufacturing yield. Since the vertical magnification of the imaging optical system is proportional to the square of the horizontal magnification, the depth of field at the same angle of view becomes deeper as the image area size is smaller when other conditions are the same. For this reason, the image obtained by the electronic imaging device has an extremely pan-focus impression image as compared with the image obtained by the silver halide camera, and there is a problem that it is not suitable for so-called portrait photography.
[0004]
In order to cope with this problem, it is conceivable to use an image processing technique. In other words, if it is considered that portrait photography with a film camera is achieved by using a medium telephoto lens and greatly blurring the background of a person, if the background can be blurred by performing different processing depending on the subject area, Images with similar portrait effects may be obtained. As such a technique, the present applicant has already proposed a method of performing a predetermined low-pass filter process on the “background region” designated by the operator (Japanese Patent Laid-Open No. 10-20392).
[0005]
[Problems to be solved by the invention]
However, since the above-mentioned conventional technology performs low-pass filter processing on the “background region”,
(1) The main subject is not blurred
(2) The background is uniformly blurred
Is.
[0006]
However, the blur in real photography is not like this. That is, each of the main subject and the background has a (generally) three-dimensional structure, and is itself accompanied by a blur that continuously occurs according to the depth. For example, when considering portrait enhancement, the eyes (or eyelashes) are in focus and the cheek outline is slightly blurred due to the shallow depth of field. Effective).
[0007]
Therefore, when the above prior art is simply applied, the discrepancy between the blur of the actual image and the processing features such as the above (1) and (2) is conspicuous. In other words, there is a problem that the image becomes unnatural such as a “writable image” as set on the stage or a “collage-like image” created by cutting and pasting.
[0008]
Needless to say, since it is necessary to recognize the main subject area and the background area separately, a special means for this purpose is required, and if erroneous recognition occurs, for example, for the main subject This included a very large problem that the image quality would be broken, such as a large background blur.
[0009]
In addition, the distance distribution of the subject is separately measured by some method, and image processing is performed according to the distance deviation of each subject portion accordingly (so that the larger the distance deviation is, the larger the blur is generated). You can also consider a method of simulating the blur that occurs according to the distance to each part of the subject, that is, the blur that continuously occurs according to the depth in the actual scene, but each part of the subject can be instantaneously displayed with sufficient resolution. Since it is extremely difficult to measure the distance, and it is also difficult to obtain an image completely equivalent to the blur caused by the optical system by image processing, the practicality is low.
[0010]
The present invention has been made in consideration of the above-described circumstances, and the object of the present invention is to capture an image having a blur characteristic equivalent to that obtained when an actual subject is photographed with a predetermined imaging system (for example, a silver salt camera). More specifically, an imaging apparatus capable of easily obtaining an imaging condition in which the depth blur characteristic of an imaging system including an optical system and an imaging element is equivalent to a desired characteristic, and focal length conversion To provide an apparatus.
[0011]
[Means for Solving the Problems]
  In order to solve the above-described problems, the present invention is an imaging apparatus including an imaging system including an imaging lens and an imaging element, and includes a first focal length f1 that is a focal length of an optical system of an assumed imaging system and the imaging. When the conversion between the second focal length f2, which is the focal length at the time of photographing with the optical system of the lens, is performed, the conversion is performed based on the depth blur characteristics of the assumed imaging system and the previous one.RecordingConversion means for performing the conversion based on an equal depth blur condition in which the depth blur characteristic of the imaging system of the image apparatus is equivalentThe equal depth blur condition is based on a first screen size w1 that is an imaging screen size of the assumed imaging system and a second screen size w2 that is an imaging screen size of the imaging system of the imaging device.
  f1 ² / W1 = f2 ² / W2
IsIt is characterized by that.
[0012]
As described above, in the present imaging device, the focal length is not determined for the purpose of obtaining an image with an equal angle of view, but the focal length itself is calculated based on the equal depth blur condition, thereby obtaining For an arbitrary assumed optical system (imaging system), it is possible to obtain a captured image having a depth blur characteristic (depth of field characteristic) equivalent to this.
[0013]
The equal depth blur condition is expressed by the following equation based on the first screen size w1 that is the imaging screen size of the assumed imaging system and the second screen size w2 that is the imaging screen size of the imaging system of the imaging device, f1²/ W1 = f2²It is preferable to use / w2. That is, when obtaining the second focal length f2 that provides the depth blur characteristic (depth of field characteristic) equivalent to the case where the first focal length f1 that is the focal length of the optical system of the assumed imaging system is used. The second focal length f2 is f1 · (w2 / w1).^1/2Given in.
[0014]
Further, when the imaging lens is configured to have a variable focal length, the value of the second focal length f2 obtained by the input means for designating the first focal length f1 and the conversion means. It is desirable to provide a focal length setting means for setting the focal length of the imaging lens. As a result, the focal length of the imaging lens can be automatically adjusted to a state where an equal depth blur characteristic can be obtained. Further, by providing means for displaying the value of the second focal length f2 obtained by the conversion means instead of the focal length setting means, the photographer manually adjusts the focal length of the imaging lens to the display value. Various configurations can also be used.
[0015]
When the imaging lens has a variable focal length, a recognizing unit that recognizes the focal length of the imaging lens that is the second focal length f2, and a second recognized by the recognizing unit. Display means for displaying the value of the first focal length f1 obtained by the conversion means based on the value of the focal length f2. This presents the photographer with which focal length in the assumed imaging optical system the depth blur characteristic of the captured image obtained at the focal length of the current imaging lens set automatically or manually. It becomes possible.
[0016]
Further, according to the present invention, conversion is performed between the first focal length f1 that is the focal length of the optical system of the assumed imaging system and the second focal length f2 that is the focal length of the optical system of the used imaging system. A conversion unit, and the conversion unit is configured to perform the conversion based on an equal depth blur condition in which a depth blur characteristic of the assumed imaging system and a depth blur characteristic of the used imaging system are equivalent to each other. A conversion device is provided.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a digital camera according to an embodiment of the present invention.
[0018]
In the figure, 101 is a variable focus zoom lens system composed of various lenses, 102 is a lens driving mechanism for zoom driving the lens system 101, 103 is an exposure control mechanism including an aperture and a shutter of the lens system 101, 104 is a filter, 105. Is a CCD color image sensor with a built-in color filter, 106 is a CCD driver for driving the image sensor 105, 107 is a preprocess circuit including an A / D converter, 108 is a color signal generation process, matrix conversion process, etc. A digital process circuit for performing various kinds of digital processing, 109 is a card interface, 110 is a memory card for recording a photographed image, and 111 is an LCD image display system.
[0019]
Also, 112 in the figure is a system controller (CPU) 112 for overall control of each part, 113 is an operation switch system composed of various SWs, 114 is an operation display system for displaying operation states and mode states, 115 Is a lens driver for controlling the lens driving mechanism 102, 116 is a strobe as a light emitting means, 117 is an exposure control driver for controlling the exposure control mechanism 103 and the strobe 116, and 118 is for storing various setting information and the like. A non-volatile memory (EEPROM) is shown.
[0020]
As the CCD image sensor 105, for example, a 2/3 inch size or 1/2 inch size is used.
[0021]
In the digital camera of the present embodiment, the system controller 112 performs all the control in an integrated manner, and controls the shutter device included in the exposure control mechanism 103 and the drive of the CCD image sensor 105 by the CCD driver 106 to perform exposure. (Charge accumulation) and signal readout are performed, taken into the digital process circuit 108 via the pre-process circuit 107, subjected to various signal processing, and then recorded on the memory card 110 via the card interface 109. It has become.
[0022]
With this digital camera, the same depth of field (depth of field) characteristic as a Leica frame camera can be obtained, regardless of the conventional equal field angle condition in which the focal length is determined for the purpose of obtaining an image with the same field angle. The focal length of the lens system 101 as described above is obtained and used. For example, when the focal length of a desired Leica frame camera is input from the operation switch 113 or the like, the lens system 101 is zoom-driven to such a focal length that an equal depth blur characteristic (equal depth of field characteristic) can be obtained. The Thereby, it is possible to obtain a captured image having a depth blur characteristic (depth of field characteristic) equivalent to an arbitrary assumed optical system (imaging system) such as a Leica frame.
[0023]
In order to obtain the focal length for obtaining such an equal depth blur characteristic, the system controller 112 is provided with a focal length conversion unit 112a. The focal length conversion unit 112a performs conversion between the focal length f1 of an assumed imaging system such as a Leica frame camera and the focal length of the lens system 101. This conversion is executed based on an equal depth blur condition in which the depth blur characteristic of the assumed imaging system is equivalent to the depth blur characteristic of the imaging system of the digital camera. In this embodiment,
f1²/ W1 = f2²/ W2
The depth blur condition is used. Here, f1 is the focal length of the assumed imaging system, f2 is the focal length of the lens system 101, w1 is the imaging screen size of the assumed imaging system, and w2 is the imaging screen size of the CCD imaging device 105. When obtaining a focal length f2 at which a depth blur characteristic (depth of field characteristic) equivalent to the case of using the focal length f1 that is the focal length of the optical system of the assumed imaging system is obtained, f2 is expressed as f1 · (w2). / W1)^1/2Given in.
[0024]
(Quantitative analysis of depth blur characteristics)
Hereinafter, in order to clarify the meaning of the above-mentioned equal depth blur condition, a quantitative analysis is performed on the depth blur characteristics.
[0025]
1 Depth blur function DOF
All the following analyzes are performed only in geometric optics and in the category of idealized conditions (aberration-thin lens). In other words, assuming the necessary condition for obtaining an ideal image, the blur characteristic obtained at that time is handled.
[0026]
There are only two basic formulas used for analysis.
[0027]
[Expression 1]

[0028]
Where a is the subject distance, b is the imaging distance, f is the focal length of the lens, δ is the diameter of the circle of confusion, F is the aperture ratio (F number) of the lens, and d is the defocus amount = imaging surface (planned focal plane). ) And the imaging plane (focusing plane), and when the imaging plane is shifted to the lens (subject) side, positive and reverse are negative.
[0029]
Equation (1) is called the “imaging formula”. However, in the so-called “optical”, the distance to the subject side is generally considered negative, but in this example, the actual distance is positive.
[0030]
In Formula (2), the circle of confusion refers to a light that is emitted from one point of the subject and that is supposed to be imaged at one point on the in-focus plane spreads in a disk shape because the imaging surface is displaced, Its diameter is the circle of confusion. In other words, this circle of confusion is a quantitative expression of blur caused by defocusing.
[0031]
Here, the meanings of the expressions (1) and (2) will be described with reference to FIGS. 2 and 3.
As shown in FIG. 2, it is assumed that the subject eye having a height x from the optical axis at the subject distance a is in focus at the imaging distance b to produce an inverted image wafer having a height y. Since the light rays parallel to the optical axis pass through the focal points, △ Ikia and △ Kikike and △ Ekau and △ Okake are similar to each other.
x / (af) = y / f
y / (b−f) = x / f
Is obtained. If the ratio y / x is eliminated from these two equations, the imaging formula (1) is obtained.
The ratio y / x is the imaging magnification and is often represented by the symbol m. If you transform the above equation,
Magnification m = f / (af) = b / a
It can be shown easily.
[0032]
As shown in FIG. 3, the size of the circle of confusion on the imaging surface depends on the aperture A of the lens.
(1) There are two cases where the imaging distance is smaller than the imaging surface distance b (when the actual focal point is tsu) and (2) when it is larger (when it is the same). From (1) △ Tatsutsu and △ Tetsutsu or (2) △ Tachitsu 'and △ Tetsutsu'
(1) A / (b−d) = δ / d or (2) A / (b + d) = δ / d
However, the sign of d is treated as positive on the basis of the case of (1), and negative in the case of (2), so that one common relational expression is used in both cases.
A / (b−d) = δ / | d |
It can be. Using this formula and the definition of the F value, F = f / A, the above-described formula (2) of the circle of confusion is obtained.
[0033]
Here, a blur = a circle of confusion that occurs with respect to the front and rear subjects when the main subject at the distance a is focused and imaged is considered. The focal plane of the subject shifted backward by the distance Δa with respect to the distance a (the subject shifted forward is included when Δa is negative) is the imaging plane (which is equal to the focal plane of the main subject). Therefore, if the deviation amount is Δb and applied to the above equations (1) and (2),
[0034]
[Expression 2]

[0035]
By solving Equation (3) for Δb and substituting into Equation (4), Δb is eliminated,
[0036]
[Equation 3]

[0037]
Get. Here, it is considered that the distance deviation Δa is a parameter representing the depth of the subject (photographing target space), rewritten to the symbol D, and further divided by the screen size w to be normalized.
[0038]
[Expression 4]

[0039]
The standardization by the screen size w is “in an imaging system with different screen sizes, even if the blur is physically the same size, the relative blur generated in the image is different”, so this is evaluated with the same evaluation scale. Is for. To be easy to understand, this corresponds to the size of the blur when the entire screen is stretched to the same size (displayed on the same size display in full screen).
[0040]
When w is a diagonal length of the imaging screen and a traditional allowable circle of confusion circle size of 33.3 μm for depth of field calculation in a silver salt 35 mm (Leica frame) size camera is considered, δ / w = 1/1300 Since it is easy to think based on this, it is 1300 times the equation (6).
[0041]
[Equation 5]

[0042]
Is called the Depth Out-focus Function.
[0043]
That is, the depth blur function DOF is a function representing how much the subject shifted by the depth D with respect to the focused subject surface is blurred. Size (equivalent to 33.3 μm in a Leica frame camera). Note that when viewing a photograph from a practical depth of field, the range that appears to be roughly in focus depends on the enlargement magnification of the photograph, but in many cases is within about twice this, or even larger. It feels blurry about 4 to 5 times or more.
Equation (7) is an exact solution that does not include approximation. However, except for the case of super macro photography, the last term is = 1, so in the normal case, the following approximation equation (7) ′ may be used. good.
[0044]
[Formula 6]

[0045]
For the sake of clarity, the approximate expression (7) 'is used when the conclusion is not affected. The numerical calculation of the exemplary graphs shown in FIGS. 5 to 8 uses the exact formula (7). Also, the coefficient terms in (7) and (7) '
[0046]
[Expression 7]

[0047]
Is called the depth blur coefficient DOC (Depth Out-focus Coefficient). In the DOF equation, the function shape (versus variable D) of the depth blur when the shooting distance a is given is the same, and its value is proportional to the depth blur coefficient DOC (DOC is the DOF graph of FIGS. 5 to 8). This is a scaling factor in the vertical axis direction).
[0048]
Here, for systems with different imaging sizes w, considering that the focal length proportional to the screen size is used as a condition for keeping the angle of view equal,
Define the angle of view coefficient vc ≡ w / f. In order to facilitate understanding of the meaning of the view angle coefficient, FIG. 4 shows the relationship between the focal length f and the view angle coefficient vc for each screen size w. For example, when the Leica frame size is f = 50 mm, the angle of view coefficient is vc = 0.87, but the focal length for obtaining a captured image with the same angle of view as 2/3 size is f = 12.7 mm. In the 1/2 size, f = 9.2 mm. In addition, when the Leica frame size is f = 100 mm, the angle of view coefficient vc = 0.43, but with the 2/3 size, the focal length for obtaining a captured image with the same angle of view is f = 25.4 mm. In the 1/2 size, f = 18.5 mm.
[0049]
Now, in order to apply the equal angle of view condition, substituting f = w / vc into equation (7) '
[0050]
[Equation 8]

[0051]
Get. Depth blur coefficient DOC = (1 / F) ・ (w / vc²).
[0052]
Since vc is a constant as long as shooting is performed with the same angle of view, and the subject distance a is the same when shooting with the same composition, the depth blur coefficient DOC (and therefore the depth blur function DOF (D)) is as long as shooting with the same F value. It can be seen that it is proportional to w. For this reason, an image taken with a digital camera is less blurred than that of a silver halide camera. For example, in the case of 2/3 size (diagonal length of 11 mm), w is almost ¼ of the Leica frame, so that only ¼ blur occurs.
[0053]
Also, from this equation (8), if w / F does not change, DOF (D) will not change. Therefore, if the aperture can be opened as much as the screen size is small (apart from the slight difference of approximate terms). It can also be seen that the same depth blur characteristics can be obtained.
[0054]
2. Illustration of DOF
FIG. 5 and FIG. 6 show the depth blurring function when imaging is performed under the conditions described above. The blur is proportional to the screen size. As a result, the depth becomes deeper as the screen size becomes smaller. In particular, at the angle of view corresponding to f = 50 mm in FIG. It can be read that there is an extreme difference in results that the 2/3 size or 1/2 size is almost close to the pan focus state.
[0055]
3. Equivalent blur imaging conditions at equal F
In view of such a reality, for example, consider a method of obtaining the same DOF even with an equal F value. Unfortunately, looking at equation (8), this is not possible as long as at least the equal field angle condition vc = const is maintained. Therefore, if it is not necessary to have an equal angle of view, in equation (8)
w / vc²  = Const
It turns out that Accordingly, the angle of view coefficient vc may be set to a value proportional to the square root of the screen size w. For example, if the screen size is 1/4 times the reference, the angle of view coefficient is (1/4)^1/2   = 1/2 times, so that the equivalent (equivalent angle of view conversion) focal length should be doubled. (The actual focal length f is
f²/ W = w / vc² = From const, (1/4)^1/2   = 1/2 times. )
When this is expressed by a general formula, when f1 is the focal length of the assumed imaging system, f2 is the focal length of the lens system 101, w1 is the imaging screen size of the assumed imaging system, and w2 is the imaging screen size of the CCD imaging device 105, The depth blur condition is
f1²/ W1 = f2²/ W2
It becomes.
[0056]
7 and 8 show the depth blur characteristics of 2/3 size when the focal length (field angle coefficient) is halved under the same aperture condition as in FIGS. is there. Naturally, the same characteristics as those of the Leica frames of FIGS. 5 and 6 are obtained. That is, it can be said that the depth blur characteristic seen by the observer when the entire screen is displayed in the same photo size (display size) is completely the same as that in the case of the silver halide camera (Leica frame imaging) as a reference. However, in this case, it should be noted that the same image is not obtained because the narrow field angle range is captured by breaking the equal field angle condition.
Next, specific operation control of this embodiment will be described. In the following, a case where a Leica frame camera is used as an assumed imaging system serving as a reference and a 2/3 inch size CCD imaging device 105 is used will be considered.
[0057]
(First example)
First, a first operation example using focal length conversion control will be described with reference to the flowchart of FIG.
First, under the control of the system controller 112, the value of the focal length f1 of the assumed imaging system (for example, f1 = 50 mm) is input by the operation of the operation switch 113 by the photographer (step S11). The value of the focal length f1 is sent to the focal length conversion unit 112a. In the focal length conversion unit 112a, a conversion process is performed to calculate the value of f2 capable of obtaining equal depth blur characteristics according to the imaging screen size ratio of w1 and w2 (step S12). In this case, since the imaging screen size ratio is 1/4, f2 = 25 mm is obtained as the focal length ratio 1/2 (f2 = f1 × 1/2) (reference: the focal length ratio 1/2 (in the case of the equal field angle condition) f2 = f1 × 1/2 = 12.5 mm)).
[0058]
In the configuration or mode in which the focal length (imaging field angle) of the lens system 101 is manually adjusted, the value f2 obtained by the focal length conversion unit 112a is displayed on the operation display system 114, the LCD 111, or the like by the system controller 112. It is displayed (step S13). When the photographer takes an image after adjusting the focal length (image angle of view) of the lens system 101 to f2, the angle of view becomes narrower than the Leica frame camera, but the depth blur characteristic (depth) is about 50 mm. An image almost equivalent to is obtained.
[0059]
In the configuration or mode in which the focal length (imaging field angle) of the lens system 101 is automatically adjusted by zoom driving, the system controller 112 uses the lens driver 115 and the lens driving circuit 102 to zoom the lens system 101. By driving, the focal length of the lens system 101 is automatically set to f2 obtained by the focal length conversion unit 112a (step S14). Even in this case, an image having a depth blur characteristic (depth) substantially equivalent to that of the Leica frame camera 50 mm can be obtained.
[0060]
(Second example)
Next, a second operation example using focal length conversion control will be described with reference to the flowchart of FIG.
In this example, the focal length of the current lens system 101 set automatically or manually is detected, and the depth blur characteristic of the captured image obtained by the setting corresponds to which focal length in the Leica frame camera. Is presented to the photographer. That is, first, at the time of photographing, the focal length of the lens system 101 is set to a predetermined value by numerical designation by the photographer or known T ← → W drive including manual (step S21). The system controller 112 recognizes the set value of the current focal length f2 of the imaging lens system 101 set automatically or manually in this way (step S22). When zoom driving is performed with numerical designation, the numerical value input or designated by the photographer is recognized as the current focal length f2, and in the case of T ← → W driving including manual operation, the lens driving circuit 102 or A known zoom encoder or the like provided in the lens driver 115 or the like detects the current zoom value and recognizes it as the focal length f2. The zoom mechanism of the lens system 101 may be a multistage switching type. This is the same in the case of the first example described above.
[0061]
Next, the system controller 112 obtains the value of f1 corresponding to the current focal length f2 using the focal length conversion unit 112a (step S23), and displays it on the operation display system 114, the LCD 111, etc. (step S24). ). In this case, a numerical value twice as large as the current f2 is displayed as f1. This makes it easy to determine which focal length is the same as the blur characteristic when using a Leica frame camera.
[0062]
Next, operations when implemented as a single focal length conversion device instead of a digital camera will be described as third and fourth examples. In this case, the focal length conversion device is the remaining part excluding the imaging system and the recording system from the configuration of FIG. 1, that is, the operation switch system 113 as the input mechanism, the operation display system 114 as the display mechanism, and the system controller 112. Can only be configured.
[0063]
(Third example)
First, by the operation of the operation switch system 113 by the operator, values of the imaging screen size w1 of the assumed imaging system, the imaging screen size w2 of the used imaging system, and the focal length f1 of the assumed imaging system are input (step S31). These input values are sent to the focal length conversion unit 112a. In the focal length conversion unit 112a, a conversion process for calculating a value of f2 capable of obtaining an equal depth blur characteristic is performed according to the imaging screen size ratio of w1 and w2 (step S32). The value of f2 is displayed on the operation display system 114 (step S33). As the imaging screen size w1 of the assumed imaging system, the screen size of the Leica frame is stored as a default value, and when w1 is not input, conversion is performed with the screen size of the Leica frame = w1.
[0064]
(Fourth example)
In contrast to the third example, this example is an example in which the focal length f2 of the used imaging system is converted to the same blurring characteristic when the assumed imaging system is used. First, values of the imaging screen size w1 of the assumed imaging system, the imaging screen size w2 of the used imaging system, and the focal length f2 of the used imaging system are input by the operation of the operation switch system 113 by the operator (step S34). These input values are sent to the focal length conversion unit 112a. In the focal length conversion unit 112a, a conversion process is performed to calculate the value of f1 that has the same depth blur characteristic as f2 in accordance with the imaging screen size ratio of w1 and w2 (step S35). The value is displayed on the operation display system 114 (step S36). As in the case of the third example, the Leica frame screen size is stored as a default value as the imaging screen size w1 of the assumed imaging system. When w1 is not input, the Leica frame screen size = w1. Conversion is performed.
[0065]
In addition, this invention is not limited to embodiment mentioned above. In the present embodiment, the assumed imaging system is a 35 mm silver salt film camera, and the embodiment camera is a digital camera. However, in the above, only the consideration and processing based on the difference in screen size are the only conditions. It is clear that the focal length conversion processing of the invention is applicable to general equal-depth blur photography under the same F-number when the screen sizes are different, regardless of the system such as the silver salt film and the electronic imaging system. . In the embodiment, the diagonal length of the screen is used as the imaging screen size w. However, the aspect ratio is naturally used for conversion between imaging systems in which the screen aspect ratio (aspect ratio) is the same (that is, the screen shape is similar). When converting between imaging systems having different sizes, not only the diagonal length but also an arbitrary one-dimensional quantity representing the size of the screen such as a horizontal length (screen width), a vertical length (screen height), etc. is used as the screen size w. good. Further, it can be applied regardless of whether the camera is a still camera or a movie camera.
[0066]
In addition, the present invention can be variously modified without departing from the scope of the invention in the implementation stage. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.
[0067]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to realize imaging having a blur characteristic equivalent to that obtained when an actual subject is photographed by a predetermined imaging system (for example, a silver halide camera).
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an electronic camera according to an embodiment of the present invention.
FIG. 2 is a view for explaining an imaging formula of an imaging optical system applied to the embodiment.
FIG. 3 is a view showing the relationship between the size of a circle of confusion and the defocus amount of the imaging optical system applied to the embodiment.
FIG. 4 is a view showing a relationship between a focal length and an angle of view coefficient in each of an imaging optical system and an assumed imaging system applied to the embodiment.
FIG. 5 is a first diagram showing depth blur characteristics in each of an imaging optical system and an assumed imaging system applied to the embodiment;
FIG. 6 is a second diagram showing depth blur characteristics in each of the imaging optical system and the assumed imaging system applied to the embodiment.
FIG. 7 is a third diagram showing depth blur characteristics in each of the imaging optical system and the assumed imaging system applied to the embodiment.
FIG. 8 is a fourth diagram showing depth blur characteristics in each of the imaging optical system and the assumed imaging system applied to the embodiment.
FIG. 9 is a flowchart showing a first operation example of the embodiment;
FIG. 10 is a flowchart showing a second operation example of the embodiment;
FIG. 11 is a flowchart showing a third operation example of the embodiment;
FIG. 12 is a flowchart showing a third operation example of the embodiment;
[Explanation of symbols]
101 ... Lens system
102: Lens drive mechanism
103. Exposure control mechanism
104 ... Filter
105 ... CCD color image sensor
106 ... CCD driver
107: Pre-processing section
108 ... Digital Process Department
109 ... Card interface
110: Memory card
111 ... LCD image display system
112 ... System controller (CPU)
113 ... Operation switch system
114 ... Operation display system
115 ... Lens driver
116 ... Strobe
117 ... Exposure control driver
118: Non-volatile memory (EEPROM)
112a: Focal length conversion unit

Claims (5)

An image pickup apparatus including an image pickup system including an image pickup lens and an image pickup element, which is a first focal length f1 that is a focal length of an optical system of an assumed image pickup system and a focal length at the time of shooting of the optical system of the image pickup lens. when performing the conversion between the second focal length f2, the conversion is based on the equal depth blur conditions and depth blur characteristic of the imaging system of the depth blur characteristic before and Symbol imaging device of the assumed image pickup system is equivalent to A conversion means for performing the conversion , wherein the equal depth blur condition is a first screen size w1 that is an imaging screen size of the assumed imaging system and a second screen that is an imaging screen size of the imaging system of the imaging device; Based on size w2
f1 ² / w1 = f2 ² / w2
Imaging device, characterized in that it. Conversion means for converting between the first focal length f1 which is the focal length of the optical system of the assumed imaging system and the second focal length f2 which is the focal length of the optical system of the used imaging system; The means is configured to perform the conversion based on an equal depth blur condition in which a depth blur characteristic of the assumed imaging system and a depth blur characteristic of the used imaging system are equivalent, and the equal depth blur condition is the assumption imaging blur Based on the first screen size w1 that is the imaging screen size of the system and the second screen size w2 that is the imaging screen size of the used imaging system
f1 ² / w1 = f2 ² / w2
The focal length conversion device characterized by being. An image pickup apparatus including an image pickup system including an image pickup lens and an image pickup element, which is a first focal length f1 that is a focal length of an optical system of an assumed image pickup system and a focal length at the time of shooting of the optical system of the image pickup lens. In performing the conversion between the second focal lengths f2, the conversion is based on an equal depth blur condition in which the depth blur characteristics of the assumed imaging system and the depth blur characteristics of the imaging system of the imaging apparatus are equivalent, and The conversion is performed when an equal angle of view condition based on the first screen size w1 that is the imaging screen size of the assumed imaging system and the second screen size w2 that is the imaging screen size of the imaging system of the imaging apparatus is not satisfied. Having a conversion means,
The imaging lens has a variable focal length, and is obtained by an input unit for designating the first focal length f1, which is a focal length of the optical system of the assumed imaging system serving as a reference, and the conversion unit. An imaging apparatus, comprising: a focal length setting unit that automatically sets a focal length of the imaging lens to the value of the second focal length f2. An image pickup apparatus including an image pickup system including an image pickup lens and an image pickup element, which is a first focal length f1 that is a focal length of an optical system of an assumed image pickup system and a focal length at the time of shooting of the optical system of the image pickup lens. In performing the conversion between the second focal lengths f2, the conversion is based on an equal depth blur condition in which the depth blur characteristics of the assumed imaging system and the depth blur characteristics of the imaging system of the imaging apparatus are equivalent, and The conversion is performed when an equal angle of view condition based on the first screen size w1 that is the imaging screen size of the assumed imaging system and the second screen size w2 that is the imaging screen size of the imaging system of the imaging apparatus is not satisfied. Having a conversion means,
The imaging lens has a focal length that is variably set by a manual setting by a photographer , and an input unit that designates the first focal length f1 that is a focal length of an optical system of the assumed imaging system that serves as a reference. An image pickup apparatus comprising: display means for displaying a value of a second focal length f2 as a focal length at the time of photographing of the optical system of the imaging lens obtained by the conversion means. An image pickup apparatus including an image pickup system including an image pickup lens and an image pickup element, which is a first focal length f1 that is a focal length of an optical system of an assumed image pickup system and a focal length at the time of shooting of the optical system of the image pickup lens. In performing the conversion between the second focal lengths f2, the conversion is based on an equal depth blur condition in which the depth blur characteristics of the assumed imaging system and the depth blur characteristics of the imaging system of the imaging apparatus are equivalent, and The conversion is performed when an equal angle of view condition based on the first screen size w1 that is the imaging screen size of the assumed imaging system and the second screen size w2 that is the imaging screen size of the imaging system of the imaging apparatus is not satisfied. Having a conversion means,
The imaging lens has a variable focal length, and a recognition means for recognizing a current focal length set automatically or manually of the imaging lens, which is the second focal length f2, and the recognition Display means for displaying the value of the first focal length f1 as the focal length of the optical system of the assumed imaging system, which is a reference obtained by the conversion means based on the value of the second focal length f2 recognized by the means. An imaging device characterized by comprising:

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