I have two Nikon D70's and several excellent lenses. Although not hugely experienced Iam not a beginner photographer. I understand the concept of depth of field and its effects. However I remain mystified as to the value of the DoF preview button. I feel I can get a clearer view of depth of field through the viewfinder without use of this function(after focussing) than with it. So far no one has been able to explain to me what exactly I shoud be seeing through the viewfinder when I press the DoF preview button. It is never explained in photography books or tutorials except to say that the DoF preview button enables you to see exactly the DoF that you will get at a certain aperture etc. It seems to me that it is actually harder to see DoF when the button is presssed as the image becomes darker at small apertures and seems unchanged at larger ones. This issue has frustrated me for several years and I would love to understand what it is i am missing!Can you help? denise.
That's a really good question, Denise.
One problem is that a D70 viewfinder is dark to start with. I don't notice this when shooting with mine unless I pick up my old Pentax Spotmatic for some reason, and then I am reminded how bright an optical viewfinder can be. So, in many cases, you will find the DOF preview useless not because it isn't working, but because the scene is simply too dark for you to see the differences.
Second thing is to notice what DOF you are seeing when you DON'T have DOF pressed. I think all modern cameras give you viewfinder at wide open aperatures -- so until you press DOF, you are seeing the focal depth produced by your lens' widest aperature. So don't expect to see much difference if you hit DOF with the aperture set at 2.2 on a F/1.8 lens -- you're comparing very similar lens apertures.
In fact, I notice that with my F/1.8 lens, I don't see any differences in where my focus lies until I have closed the lens down to maybe F/8. But beyond there, I can clearly see that more and more of the scene is in focus.
If you're still curious but not seeing it, try some test shots. Change the aperture and using shutter time to compensate, and see if your photo DOF matches the preview.
Hope that makes sense!
-- eastpole
Posted on Dec 07, 2007
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Dear Eastpole, thank you for such a lengthy articulate and logical explanation! I will certainly try out the thngs you have suggested including a comparison with a Pentax Spotmatic that I have inherited from a family member. Your comment about the increased difficulty in seeeing DOF with a D70 also helped me to feel less of an idiot! i really appreciate your time and help. many thanks. waratah.
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