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Forum: Pentax SLR Lens Discussion
07-20-2015, 05:41 PM
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I'm pretty sure the original intent of the concept of equivalence was to allow film based FF photographers to get a handle on crop mode digital cameras so they could maintain their traditional relationship with FOV and DOF. This would have been used as a simple guide to allow transition across formats but has mutated into a ridiculous online p*ssing contest.
Some of the posts here are quite personal and denigrating in nature. I'd like to say that if your true intent is to win an argument then you don't win any arguments by laughing at people and putting them into a competitive orientation.
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Forum: Pentax SLR Lens Discussion
07-15-2015, 02:54 AM
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Forget I mentioned it. For some unknown reason I was thinking the registration distance was different for FF and APS-C. I've been thinking a lot about MF lately and I have been preparing to mount an exhibition of my late mother's artwork. Lots of stress. :o
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Forum: Pentax SLR Lens Discussion
07-13-2015, 09:22 PM
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Well said.
I tried to simplify this idea even further by using a magnifying glass as an example, which was decried instantly so I didn't bother to reply.
Also, the inverse square law regarding light fall-off, must play a factor in helping FF lenses on APS-C due to the smaller distance to the sensor, although I haven't worked out by how much.
---------- Post added 14-07-15 at 01:57 PM ----------
Before you view the picture it is both alive and dead. ;)
---------- Post added 14-07-15 at 02:02 PM ----------
Equivalence is a useful concept while people are moving between formats, but after a while one doesn't think about it anymore. I started out with a K2, LX and MX back in the day and so I thought in terms of FF glass. When I finally got a K5 I had to relearn my relationships with Aperture, DOF, FOV and FL. After a while, as you say, you learn the nature of the gear and format doesn't really count as long as you are familiar with the gear and know how to achieve what you want.
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Forum: Pentax SLR Lens Discussion
07-13-2015, 04:24 AM
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Dx0 "normalizes" all images to 8MP (IIRC) and a lot of noise gets swallowed up by that process.
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Forum: Pentax SLR Lens Discussion
07-12-2015, 05:02 PM
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Focal Ratio is a measure of the ratio of the focal length divided by the aperture of the glass.
The amount of light captured (brightness) depends on the size of the sensor relative to the the exit pupil of the lens. If you don't believe this then experiment with a magnifying glass, making large and small projections on a piece of paper, and you will find that the smaller the projection, the brighter the image.
DOF does change with format (FOV) and is due to the 1.5x extra magnification that a standard print or monitor presents. People say "oh, it's still a 50mm lens etc" but they overlook the extra TELECONVERTER EFFECT of the output medium.. which, combined with change in FOV, changes the DOF.
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I've uploaded a couple of screen grabs from LR to show (as closely as my sloppy methodology allows) how a 24mm lens @F2.8 is a "match" for a 36mm lens @f4-4.5.
This is a Tamron 24-70 F2.8 VC lens on a D810 in FF Mode(36mm) and 1.5x Crop Mode(24mm)
They look close apart from the exposure time. The light changed a bit and it's windy (shots taken about 20 minutes ago). I believe that f/4 @36mm is a closer match however.
The close-up 100% shows the relative sizes of the OOF specular highlights to the subject. They look close in each image.
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