JoeW
Been spending a lot of time on here!
- Joined
- Dec 17, 2013
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If I wanted to use low apertures (like 1.8-2.8) how far away can I be for it (the persons EYES) to still be tack sharp?
I know that It make the DOF much smaller, But I have no idea how to calculate what distance I should be from the subject. I have tried DOF calculators, but they don't really help.
Please help me clear this up.
I think you're confusing two different concepts here. Lots of people use wide-open apertures (f1.8, f2.0) in low light b/c it maximizes the amount of light coming in to the camera and they want to use only ambient light (either don't have or don't want to use speed lights). And they recognize that the DoF gets narrower as the aperture gets wider.
But you're asking about two separate issues here. First, is the actual DoF. As Braineac pointed out, the actual size of the DoF (even if it's set at f1.8) varies depending upon how far away you are from your subject. But I don't think that's what you mean to ask. My apologies if I'm wrong but it sounds to me what your'e really asking is how close can you be to the subject. And that's a function of the lens, not the aperture. I've got a macro lens that allows me to shoot mere inches from the subject and still be in focus (and with a very narrow DoF).
Also, as others have pointed out, focus and being "tack sharp" aren't the same. You can be in-focus and end up with a blurry picture b/c the light is so slow you're shooting at 1/20th or 1/15th shutter speed. That's going to produce blur with a living object (and that assumes you're rock solid still which you aren't--you pushed down the shutter release, you were breathing...all things that moved the camera). If your focus is on tack sharp photos, it gets in to things like:
--stable platform (camera on a tripod, wireless release)
--quality glass
--stable subject (ideally an inanimate one that doesn't move or breath).