11-20-2011, 10:03 PM
[quote name='Brightcolours' timestamp='1321732917' post='13043']
I agree with Studor13, DOF "scales" and calculation tools are a bit nonsensical.
You use a certain aperture size for either the look of the photo, or the light conditions. Not to get a "measured" depth in focus (which is nonsense anyway).
If you do not want a blurry background, no need for a 85mm f1.8 lens. If you need a whole person somewhat in focus, no need to fiddle with DOF blah either, just set the lens to f5.6 and you will be fine.
85mm on your Nikon gives approximately the field of view of a 85 x 1.5 = 127mm lens.
[color="#0000ff"]The aperture of the lens is 85mm / 1.8 = 47.2mm. For that 127mm lens that means: 127mm focal length, 47.2mm aperture: 127 / 47.2 = f2.69
[/color]
Now that did not make your head hurt, I am sure.. Very simple really <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />
[/quote]
Quoted again, but now with highlight in blue and bolded.
[quote name='Brightcolours' timestamp='1321824328' post='13072']
You are totally wrong in thinking what I wrote is wrong.![[Image: dry.gif]](https://forum.photozone.de/public/style_emoticons/default/dry.gif)
Nowhere did I state the focal length changes, nor did I state anywhere the aperture changes. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/huh.gif' class='bbc_emoticon' alt='
' /> [/quote]
Well, maybe I read to much into it: you didn't mention it is equivalent to... etc. That is, IMO, quite a difference.
Well, the CoC stays important, because DoF is calculated based on a certain size CoC. IOW, if it is non-existent, then neither is DoF. CoC is part of the definition of perceived sharpness at a certain magnification and viewing distance, based on the (average) acuity of the human eye. And DoF is delimited by the area which is perceived as sharp according to this definition.
Whether you choose a quick and dirty method to calculate apparent aperture doesn't matter, but please do indicate that it is an equivalent aperture, compared to FF. That's what I meant by saying that the aperture stays the same. Same with FL. The aperture doesn't suddenly change because one is using a crop camera, neither does the FL. The effect is different, that's all.
Regards, Wim
I agree with Studor13, DOF "scales" and calculation tools are a bit nonsensical.
You use a certain aperture size for either the look of the photo, or the light conditions. Not to get a "measured" depth in focus (which is nonsense anyway).
If you do not want a blurry background, no need for a 85mm f1.8 lens. If you need a whole person somewhat in focus, no need to fiddle with DOF blah either, just set the lens to f5.6 and you will be fine.
85mm on your Nikon gives approximately the field of view of a 85 x 1.5 = 127mm lens.
[color="#0000ff"]The aperture of the lens is 85mm / 1.8 = 47.2mm. For that 127mm lens that means: 127mm focal length, 47.2mm aperture: 127 / 47.2 = f2.69
[/color]
Now that did not make your head hurt, I am sure.. Very simple really <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />[/quote]
Quoted again, but now with highlight in blue and bolded.
[quote name='Brightcolours' timestamp='1321824328' post='13072']
You are totally wrong in thinking what I wrote is wrong.
Nowhere did I state the focal length changes, nor did I state anywhere the aperture changes. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/huh.gif' class='bbc_emoticon' alt='
' /> [/quote]Well, maybe I read to much into it: you didn't mention it is equivalent to... etc. That is, IMO, quite a difference.
Quote:The DOF changes EXACTLY to what you would get with the FF equivalent I described. Does not matter if you want to approach that with the non-existent circle of confusion, or if you describe it with FF equivalence.
I did the latter. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />
Well, the CoC stays important, because DoF is calculated based on a certain size CoC. IOW, if it is non-existent, then neither is DoF. CoC is part of the definition of perceived sharpness at a certain magnification and viewing distance, based on the (average) acuity of the human eye. And DoF is delimited by the area which is perceived as sharp according to this definition.
Whether you choose a quick and dirty method to calculate apparent aperture doesn't matter, but please do indicate that it is an equivalent aperture, compared to FF. That's what I meant by saying that the aperture stays the same. Same with FL. The aperture doesn't suddenly change because one is using a crop camera, neither does the FL. The effect is different, that's all.
Regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....