Focus question and advice please!

Started 2 months ago | Questions thread
Rick Knepper
Rick Knepper Forum Pro • Posts: 17,032
Re: Baby and bathwater

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

My personal opinion is that DOF calculators are garbage in the field, especially w MF - a total waste of time unless you are using one to demonstrate the general academic theory of aperture effect on DOF in a hand-wave kind of teaching moment.

DoF calculators are not wrong but they could return an incorrect value if the wrong input is used. Also, DoF calculators assume the use of hyperfocal distance which I am not always in favor of in landscape photography.

The best DoF calculator is one's familiarity with a given camera & and its characteristics if expediency is needed. Test shooting a variety of scenes at every aperture will help educate that memory muscle. But, shooting scenes on a photo trip at a couple of apertures takes very little additional time and can help with getting familiar with the apparent DoF. Also, using equivalence (and all that this concept implies) to convert apertures one was using with a smaller format to MF should get you the same DoF and diffraction characteristics.

By the way, I am not trying to talk anyone out of using their method. I am writing this for the benefit of the OP who asked for advise.

I could be wrong and don't mean to step on anyone's like or use of these DOF apps. Have at it if you think it will cause you to dial in a smaller apperture, because that is what you need to do e MF.

I want as much DOF as I can get almost 95 percent of my shooting situations because I am not a portrait artist. I dial in as much DOF as hand held speed will allow while maintaining a decent (hopefully base) ISO and try not to go into diffraction too much. But I am no longer afraid of F 11 to get DOF in MF landscapes. Olny Superman (and maybe Erik) will see the loss of res between F8 and 11. DOF tables are a waste of time and almost always wrong with MF. No... Not almost .... They are wrong always.

No one should be afraid of f16 or f22 if these are truly needed and other techniques are not desired or advisable based on conditions at the scene and finally, if deconvolution processing is understood and used.

Also, something to think about for folks who crop images to fill a 3840x2160 monitor. If one crops from the bottom, composing a scene can take that into account and allow wider apertures to be used because the oof areas (presumably closer objects) will be cropped out.

There's a baby in that bathwater. With the right CoC dialled in, DOF calculators and tables are just fine, as far as they go. They almost always ignore diffraction and sensor pixel blur, which can be more important in some parts of the image than CoC.


Jim, you went easy on me. But I knew I was not going to get away with that post unscathed..... 😁

Greg Johnson, San Antonio, Texas

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