Depth of Field Question

[Pro-Vista]

I've done an empirical assesment, which seems to 'confirm' what I suspected, although I haven't yet got prints back to assess whether it's to do with what I see on-screen as opposed to an actual prints. (I hope that makes sense!)

[Pro-Vista]

Originally Posted by David Barry

My experience with the 1Ds MK III is that the sensor is so staggeringly sharp, that it shows every detail so precisely that you notice any imperfections in the image more than you would with an older one with lower resolution. You may just be seeing the actual performance of the lens for the first time.
I have a 24-70 L and I have been shooting less with it and more with the 35 and 50 Ls since getting the 1Ds MK III as the difference in image quality is pronounced.
I would however, certainly recommend doing a focus test and adjusting the micro adjustment in light of the results.

David.

Sorry, forgot to ask: Can you give me more info on how to do a micro-adjustment?
Thanks,
Steve

[Pro-Vista]

Originally Posted by jeffcable

The DCS/n was a 14Mpx body and it used a full frame sensor (35mm equivalent) if I am not mistaken. The Canon uses an APS-h sized sensor giving you a 1.3x field of crop. Lens focal length has an effect on depth of field and the longer the focal length the less depth of field will be available, at any given aperture.

Your 24 ~105mm lens is 35mm longer, at the 105mm end, than the 70mm of the 24~70mm lens which you used to use. If your habit is to turn the zoom ring to longest focal length, then your Canon lens will have less available absolute depth of field at 105mm (albeit somewhat negated by the smaller sensor size) than the 70mm of the the Nikon lens.

OTOH, you are shooting in a studio, and you can use a smaller aperture to regain your lost depth of field. Often, studio shooting can require that one has minimal depth of field settings so there is one possible advantage to your current lens.

Personally speaking, a lens with a maximum aperture of f/4.0 is going to be a bit too slow to produce knife-edge thin differential focus and it requires something like the 85mm f/1.2, which would most certainly be the puppy for that type of work. YMMV

I agree. I need to check actual prints (rather than on-screen assessments) to see if it's obvious. If it is, then I will shoot with a smaller aperture, which is not a particular problem in-studio, although I would be concerned in other circumstances if I am limited to using a smaller aperture to retain DoF, for obvious reasons.
Thanks,
Steve

[Pro-Vista]

Originally Posted by Doug_Kerr

Hi, P-V,


With the same format size on the two cameras, then at the same focus distance, aperture, and focal length, the depth of field should be the same. (This assumes the same visual "blur" criterion as the limit of "acceptable" misfocus when examining the images at the same overall angular size, such as at the same on-screen size viewed from the same distance.)

But at a greater focal length, the depth of field would be less. Is there any chance that you are in part making your comparison with the lenses on both rigs set at their respective maximum focal lengths?

There is another possible consideration. If your new rig yields grater actual resolution (not just "geometric" resolution, in terms of pixel dimensions), that can sometimes condition us to a greater expectation of sharpness, so that the same actual degree of blurring will seem more "offensive".


As an aside, I believe that etiquette here suggests that posters whose display name is not a form of their real name should at least use their real name in the signature.

I obviously need to 'brush up' on my etiquette!
Steve
(alias Pro-Vista - my company name)

[Pro-Vista]

Originally Posted by Duncan_Harris

You mention using "full AF function (rather than manual)". I'm relatively new to digital cameras (3 yrs) and can't compare your DCS but when using my 1Dmk11n with all focus points I believe it will first try to focus using the centre point then will focus on the nearest "subject". If you are using all points could this be causing it to focus forward and the apparent reduced DOF ?

Be interested from the more techical/experienced members to comment if I'm talking rubbish !!

Good point. I will try fewer AF points, and see how this works.
Steve
(Pro-Vista)

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