Cropping choices and their impact on depth of field

Listening to recent reviews and discussion around the Canon 5DS, 5DSR and the Leica Q you find some comment around in camera cropping options; features that let you set different crops or effective focal lengths in camera.  Likewise, there’s a note to some 5DS and 5DSR reviews that with so many pixels, one can crop in post and still have decent size files.  Of course, in all these cases you’re losing pixels and image size, and that’s the main focus of debate I encounter.

One nuance I don’t see mentioned so much is the difference in depth of field between a shot “cropped” with a camera feature or in post, versus a shot “cropped” by recomposing, moving nearer your subject.  My street portrait of Czech girl Jitka hopefully serves to illustrate the difference here.

Jitka (Stranger #35/100), London Brick Lane

Above is the main shot from last year’s street encounter with Jitka.  As well as this shot, I took another closer cropped version stepping nearer her (see below).  Depth of field, obviously, is an equation with multiple facets – the width of aperture, the focal length of the lens, but also the distance from sensor to subject, and from subject to background.  Composing more tightly, a closer crop, by stepping near your subject changes an input in that equation – by getting you nearer your subject, it gives a shallower depth of field, as many people seek in a portrait.  It has a three dimensional impact on your composition.

Cropping with a camera feature or in post has only a two dimensional impact on your composition.  It doesn’t change your depth of field, or help to drop a background.  Here’s an example to illustrate.  The first image (left/top) is a Lightroom crop of the main image above.  The second image (right/bottom) is a separate image shot by stepping closer to Jitka – helping to drop the background further out of focus.

Alternate Take - Jitka (Stranger #35/100), London Brick Lane (Simulated Crop)  Alternate Take - Jitka (Stranger #35/100), London Brick Lane

As ever it depends what you’re shooting and what effect you are seeking.  If you are shooting landscapes, seeking front to back sharpness, this nuance probably needn’t enter your considerations and the loss of file size is maybe the biggest trade off to consider.  For those shooting shallow depth of field portraits, I think it’s a valid footnote to the discussion about the advantages of these new features or pixel counts.

Sometimes the advice against cropping with a camera setting or in Photoshop is overwhelmed by “purists” who simply object on ethical grounds.  That’s a shame, as it disguises some of the tangible effects these decisions have on our images.  I’m a pragmatist, I don’t care how I get the end image.  Often that’s best done in camera, and hopefully this quick examination highlights one of the situations where that’s definitely the case!

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One thought on “Cropping choices and their impact on depth of field

  1. cool post, the top one is interesting as the curvy lines make me think of brain waves coming out of her head, and her skin tone is warmer. But the other one has better separation so I guess that would be the preferred choice.

    Like

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