11-21-2011, 12:25 AM
[quote name='Brightcolours' timestamp='1321832434' post='13085']
Ian was SPECIFICALLY asking about FF equivalence. Why would I have to specifically repeat that, if it is him I was replying to? Should be obvious to anyone, really. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> [/quote]
Well, after a few posts these subtleties tend to get lost, whether it should be obvious or not.
Well, to you they may be non-existent. In that case Airy disks probably do not exist either, and neither does diffraction. They are all used for definitions of sharpness, as in, resolution. And DoF IS based on CoC - it is the one definition used in determining the DoF, amongst others, in all those DoF calculators you can find on the internet, and funnily enough, it is also used to determine DoF scales. It is after all used for the definition of what is considered to be sharp, and the CoC size determines, at what magnification, when something is sharp or not, from an industry standard POV. And any half-decent article on DoF will show this.
Do note that changing the CoC size will change DoF drastically...
Printing at the same size is prerequisite #1, indeed. Pixel pitch is important, as there should be enough pixels to have the resolution required to make the prints look sharp at the same viewing distance. Therefore, viewing distance is important too. In short, all of these are important, and to state it once more, medium size, and hence sensor size, while creating an equal size print, or image, means that the CoC has to change in order to be able to get an image at exactly the same size, same distance with equal sharpness and DoF. That is where it all starts, CoC IOW.
Crop factor is only a derivative.
Yes, I do know that. As mentioned, I think you made it appear is if this was the new FL and the new aperture, that's all.
Regards, Wim
Ian was SPECIFICALLY asking about FF equivalence. Why would I have to specifically repeat that, if it is him I was replying to? Should be obvious to anyone, really. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> [/quote]Well, after a few posts these subtleties tend to get lost, whether it should be obvious or not.
Quote:DOF calculations are not based on CoC, the non-existent CoC is used to cover many variables which may or may not be of importance depending on what one is comparing.
Well, to you they may be non-existent. In that case Airy disks probably do not exist either, and neither does diffraction. They are all used for definitions of sharpness, as in, resolution. And DoF IS based on CoC - it is the one definition used in determining the DoF, amongst others, in all those DoF calculators you can find on the internet, and funnily enough, it is also used to determine DoF scales. It is after all used for the definition of what is considered to be sharp, and the CoC size determines, at what magnification, when something is sharp or not, from an industry standard POV. And any half-decent article on DoF will show this.
Do note that changing the CoC size will change DoF drastically...
Quote:In case of DOF equivalences, the only thing that matters is the crop factor, nothing else. Not the print size (if we print at the same size), not the pixel pitch, not the viewing distance.
Printing at the same size is prerequisite #1, indeed. Pixel pitch is important, as there should be enough pixels to have the resolution required to make the prints look sharp at the same viewing distance. Therefore, viewing distance is important too. In short, all of these are important, and to state it once more, medium size, and hence sensor size, while creating an equal size print, or image, means that the CoC has to change in order to be able to get an image at exactly the same size, same distance with equal sharpness and DoF. That is where it all starts, CoC IOW.
Crop factor is only a derivative.
Quote:BTW, it helps to differ between aperture (size in mm) and f-value. The aperture I did not change in finding out what was equivalent. The (equivalent) f-value was what changed. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='' />
Yes, I do know that. As mentioned, I think you made it appear is if this was the new FL and the new aperture, 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 ....