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06-27-2008, 08:23 AM   #1
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Crop Factor

There is no "crop factor". When will people wake up and realize this?

Thanks, I just had to get that out of my system.

06-27-2008, 08:27 AM   #2
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define crop...


an image taken on an APC sized sensor.. IF compared to a FF sensor, is in fact cropped

but again, this is only assuming that one tries to make that link between the two formats.

WHY such strong support for this reference exists is beyond me.
06-27-2008, 08:34 AM   #3
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QuoteOriginally posted by Wheatfield Quote
There is no "crop factor". When will people wake up and realize this?

Thanks, I just had to get that out of my system.
OK

But....


What other name would you give to the reduced FOV when using an APS-C sensor?
06-27-2008, 08:36 AM   #4
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QuoteOriginally posted by Ed in GA Quote
What other name would you give to the reduced FOV when using an APS-C sensor?
its only reduced if you choose to compare it to its hypothetical usage on a camera with a larger sensor/film.

considering pentax has no digital FF cameras, this comparison is irrelevant.

06-27-2008, 08:39 AM   #5
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Wheatfield, you are right. A 35mm lens is a 35mm lens. It sees what it sees, the way it sees it and has no idea what size sensor (film or electronic) is behind it. 70-80mm is a better portrait lens than a 50mm on a 35mm camera. using a 50mm on an APS-C sensor does not make it take on the characteristics that a 75mm has on full size. If you want those characteristics you would still need a 75mm lens.

There was a thread a while back where someone said that to minimize shake effect with the old maxim "shutter speed should exceed focal length", you should figure in the "crop Factor". i.e. if you have a 200mm lens on FF, use 1/200th+ shutter speed, but on APSC you would need 300+. I don't believe that as the lens produces an image circle of a given size focused at a specific point; it has no idea (and doesn't care) how much of that image is being recorded.

Last edited by Parallax; 06-27-2008 at 08:47 AM.
06-27-2008, 08:41 AM   #6
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QuoteOriginally posted by Gooshin Quote
its only reduced if you choose to compare it to its hypothetical usage on a camera with a larger sensor/film.
Golly, I thought that was the whole idea of the term.

Shame on me.
06-27-2008, 08:43 AM   #7
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QuoteOriginally posted by Ed in GA Quote
Golly, I thought that was the whole idea of the term.

Shame on me.
but the question is why would or should you care?
06-27-2008, 08:46 AM   #8
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QuoteOriginally posted by Parallax Quote
Wheatfield, you are right. A 35mm lens is a 35mm lens. It has no idea what size sensor (film or electronic) is behind it. 70-80mm is a better portrait lens than a 50mm on a 35mm camera. using a 50mm on an APS-C sensor does not make it take on the characteristics that a 75mm has on full size. If you want those characteristics you would still need a 75mm lens.

There was a thread a while back where someone said that to minimize shake effect with the old maxim "shutter speed should exceed focal length", you should figure in the "crop Factor". i.e. if you have a 200mm lens on FF, use 1/200th+ shutter speed, but on APSC you would need 300+. I don't believe that as the lens produces an image circle of a given size focused a a specific point; it has no idea (and doesn't care) how much of that image is being recorded.
While there is no "crop factor" as you say, and it is only a relitive comparison of formats, there is one point that MUST be considered. This is with respect to the "golden rule" of shutter speed = 1/focal length.

This "rule" is applied directly to 35mm format, and the ability to eliminate camera shake with respect to acceptable image sharpness for a full frame (35mm format again) 8 x 10 print.

If you enlarge beyond that, you must use higher shutter speeds. Therefore, if you make the same 8 x 10 inch print with a smaller sensor, you are using a higher enlarging magnification and you should consider this increased magnification, whether you call it crop factor or something else, in your estimation of shutter speed to produce acceptable image sharpness.

if not crop factor, what would you call it?

06-27-2008, 08:48 AM   #9
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QuoteOriginally posted by Ed in GA Quote
OK

But....


What other name would you give to the reduced FOV when using an APS-C sensor?
I call it field of view. When I shoot with my 6x7, I don't think in terms of cropping from the 4x5 format, when I shoot 4x5, I don't think in terms of a crop from a full plate (which if you are going to discuss "crop factor" the way it is bandied about would be the better reference standard), when I shoot 35mm, I don't think in terms of a crop from either 4x5 or 6x7, so why would I think of a "crop factor" with an APS-c digital SLR?

To me, it amounts to mushy thinking. The APS-C is a different format. It happens to use the same lens mount as a different format.

Out of curiosity, what is the "crop factor" of a DA70mm LTD? Or a DA14mm, or a DA 12-24, or a 21mm LTD, or the DA200 and 300 mm lenses. They aren't usable on 35mm, so why reference back to that format.
06-27-2008, 08:49 AM   #10
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how does the golden rule work against moving subjects? ehh? ehh?

also the golden rule goes out the window for people with shaky hands

it also goes out the window if you can prop yourself against a wall or something


likewise a modern age photographer should simply change this "golden rule" to something else.
06-27-2008, 08:50 AM   #11
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QuoteOriginally posted by Gooshin Quote
but the question is why would or should you care?
That question would be better asked of wheatfield since he is the one who made the original proclamation.

Personally, I'll call it whatever I wish.
06-27-2008, 08:52 AM   #12
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QuoteOriginally posted by Lowell Goudge Quote
....................This "rule" is applied directly to 35mm format, and the ability to eliminate camera shake with respect to acceptable image sharpness for a full frame (35mm format again) 8 x 10 print.

If you enlarge beyond that, you must use higher shutter speeds. Therefore, if you make the same 8 x 10 inch print with a smaller sensor, you are using a higher enlarging magnification and you should consider this increased magnification, whether you call it crop factor or something else, in your estimation of shutter speed to produce acceptable image sharpness..........................
Interesting point. I hadn't considered that aspect. Hmmmmmmmmmmmmmmm.
06-27-2008, 08:53 AM   #13
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QuoteOriginally posted by Parallax Quote

There was a thread a while back where someone said that to minimize shake effect with the old maxim "shutter speed should exceed focal length", you should figure in the "crop Factor". i.e. if you have a 200mm lens on FF, use 1/200th+ shutter speed, but on APSC you would need 300+. I don't believe that as the lens produces an image circle of a given size focused at a specific point; it has no idea (and doesn't care) how much of that image is being recorded.
The rules change when you change format. I can handhold my 6x7 at ridiculously show shutter speeds, much slower than I can handhold my K20, even with SR turned on. When I was using a Crown Graphic, I was able to handhold slower than I could hand hold my 6x7.
It's a different format, and has different rules.

Why not think of the format in it's own terms, rather than applying the rules from a different format and then applying a multiplication to get back to the format you are using?

I seem to be on a mission this morning.
06-27-2008, 09:00 AM   #14
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QuoteOriginally posted by Wheatfield Quote
.............
Why not think of the format in it's own terms, rather than applying the rules from a different format and then applying a multiplication to get back to the format you are using?
I'm for that 100%, but old ways, and thought processes, die hard. When everything finally goes FF the problem will be resolved and life will be much simpler.
06-27-2008, 09:02 AM   #15
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IF things go the FF way.
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