Depth of Field Discussion

[Capturingtheunseen.com]

This is an issue that has always been a bit puzzling to me. For starters, some of the tables I see include the camera body, and some don't. Why the reason for including it? Different sensors?

Also, I see the term "acceptable focus" used in the definition of DOF. As defined by what/who?

Finally, I wonder why so many people seem to be concerned with focusing on the eye of the target (for example, bird.) If the entire bird is within the dept of field, what difference does it make? Sometimes, trying to focus on the eye of a Cardinal at considerable distance will give you an out-of-focus image due to the AF missing the small target. Unless they are very close, and a larger bird, focusing on the body will also give you sharpness in the eye as they are on the same relative plane. A larger animal like a bear; of course I can see it then.

Here is a link to a DOF calculator, let me know what you think.

Depth of Field (DoF) calculator | PhotoPills

This Depth of Field (DoF) calculator will help you get the creative control on the design of your photos. Decide the zone of sharpness you need to tell the story you want and get your message across.

www.photopills.com

 

[JSD]

DOF is so limited with teles it’s always a balancing act between aperture, shutter speed and ISO to get everything right, especially when fast action and changing light keeps one on their toes. If the eye at least is dead sharp, the rest can be acceptable to some degree, depending on all the other factors, composition, etc. This is how I look at it.
I try to define”acceptable focus” myself, for my standards and for the photo’s appeal. I am sure there is a more technical explanation for it but I try to KISS.

 

[DRwyoming]

For starters, some of the tables I see include the camera body, and some don't. Why the reason for including it? Different sensors?

Yes, sensor size or more specifically media size has a big impact on DOF for the same focal length lens, aperture and subject distance. Having calculators where you enter a specific camera model is a convenient way of entering the sensor size.

An extreme example of this is what it took back in the day to get a from here to forever DOF in large format view cameras. It wasn't unusual to stop lenses down to f/64 to achieve the desired DOF in landscape images using large sheets of film and that's what Ansel Adams and his associates named their camera cohort, The f/64 Group.

I'm definitely in the 'eye comes first' school of focus priorities. I think we tend to accept images with soft wingtips but sharp eyes better than the other way around. But you're right it's most important for close ups where you can really see the eye detail and where a soft eye would be most distracting. And in fairness I shoot BIF in either Group or one of the Nikon Dynamic focus area modes and then I'm more or less betting that either the focus system happens to grab onto something in the same distance plane as the eye or there's enough DOF based on aperture, focal length lens and subject distance to get away with sharp enough eyes. Especially when running Group AF mode I don't always know exactly what the focus system latched onto but hope the eye is still as sharp as possible.

 

[Capturingtheunseen.com]

Yes, sensor size or more specifically media size has a big impact on DOF for the same focal length lens, aperture and subject distance. Having calculators where you enter a specific camera model is a convenient way of entering the sensor size.

An extreme example of this is what it took back in the day to get a from here to forever DOF in large format view cameras. It wasn't unusual to stop lenses down to f/64 to achieve the desired DOF in landscape images and that's what Ansel Adams and his associates named their camera cohort, The f/64 Group.

I'm definitely in the 'eye comes first' school of focus priorities. I think we tend to accept images with soft wingtips but sharp eyes better than the other way around. But you're right it's most important for close ups where you can really see the eye detail and where a soft eye would be most distracting. And in fairness I shoot BIF in either Group or one of the Nikon Dynamic focus area modes and then I'm more or less betting that either the focus system happens to grab onto something in the same distance plane as the eye or there's enough DOF based on aperture, focal length lens and subject distance to get away with sharp enough eyes. Especially when running Group AF mode I don't always know exactly what the focus system latched onto but hope the eye is still as sharp as possible.

Yep, I agree. I've heard photogs tell people "always focus on the eye." But if it's on the same plane that's all that matter. During BIF would it matter if the focus point is on the eye or the body of a duck, for example? Nope. Not in my experience. And the body is a much easier target to hit.

 

[Warren D]

With large format, you can also change your focus plane via tilts and swings. The DOF formulas use an item called circle of confusion. I won't get into the explanation, but the CoC differs based on format, ie, in modern terms, sensor size and thus the resultant DOF differs. In general, DX has about 1 stop more than FX. By the time you get to 4x5 or 8x10 you need f32-45 to get similar DOF to f11-16 on FX. Focal lengths and image circle also figure in.