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Old Mar 19, 2010, 3:44 PM   #41
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Originally Posted by TCav View Post
Oh, you do more than digress.

Originally Posted by TCav View Post
No. Light gathering ability is a function of pupil diameter. "Resolving power" is sharpness, and while varying the pupil diameter varies sharpness, that's because a smaller pupil diameter masks out optical flaws. And neither resolving power or light gathering ability has anything to do with focal length or crop factor.
Originally Posted by TCav View Post
Are you suggesting that resolving power and/or light gathering ability is in some way related to focal length and/or crop factor?
Originally Posted by TCav View Post
The pupil diameter (aperture) doesn't affect the resolving power in any way, except that lenses that don't have a great deal of resolving power can perform better if a diaphram is closed such that, for instance, portions of the lens where the polished surfaces have more variability are prevented from contributing to the image. The same is also true of the crop factor, in that, less than perfect portions of an image are simply cropped out. These methods don't actually increase the resolving power of the optics, they just block the light where the resolving power is less than perfect.
Originally Posted by TCav View Post
Light gathering ability is a function of focal length and pupil diameter. The aperture (expressed as an f-number) is a function of just those two values (f-number = focal length / pupil diameter.) All f/2.8 lenses have the same light gathering ability regardless of their focal length or the crop factor of the body they're mounted on.
And then this classic...


I would not have to digress if you simply admitted any error at all. But you're always right, and never mispeak, let alone err. You stand by all the above? I was very careful not to take them out of context.

Again, to summarize - The cropping factor in a DSLR has the value of putting more pixels on target, and by doing so is able to give us a clear view of what the lens is capable of resolving. What it cannot do is match the resolving power of the larger lens. If it cannot distinguish between two objects which are very close together, you will simply get a clarified blur.

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Old Mar 19, 2010, 4:36 PM   #42
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Guys... It's pretty obvious that this debate is going nowhere, and continuing it doesn't serve any purpose other than to confuse members that may find it.

Mark1616 wisely moved the original subject matter to a separate sticky. But, this topic has been "beaten to death" and it's obvious to me that there is not going to be any agreement.

The last time I remember this same subject being debated for so long, members lost their tempers and starting getting personal, with some good members being banned because of it, with the thread being closed as a result.

Well... I'm not inclined to let it go that far this time around, and if that makes me the "bad guy", so be it. This thread is closed.
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