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03-22-2011, 09:16 AM   #1
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the 1.5 factor

so would this efect the apature allso im saying on older lenses like take a 28mm f/2.8 would you take 28mm x 1.5 and then thake the f/2.8 and divided it by 1.5 to get an f/1.8 then???

03-22-2011, 09:30 AM   #2
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please forget you ever heard about the 1.5 factor

this single point is the worst thing to ever hit the DSLR.

the 1.5 factor really applies to the ratio of the image sensor to that of a 35mm film frame.

Lens parameters such as focal length and aperture are wholly independant on the sensor size,

focal length is defined (for a simple lens) as the distance from the focusing plane to the lens center for a subject infinitely far to appear sharp.

Aperture us the ratio of focal length to diameter of the lens

Nothing in either of the above 2 definitions about crop factor or sensor size is there?

the real change, and this is relitive to every different format of film and / or sensor is the field if view (measured as an angle) of the lens, when used with a sensor. a 50mm lens on film has a wider field of view than a 50mm lens on an ASP-C sensor (with 1.5 crop factor) but all other settings the same, and the subject enlarged to the same size in both film and ASP-C digital sensors, nothing else changes, not Depth of field, not esposure, not the blurr form camera shake, NOTHING AT ALL

People get confused about the crop factor but all it really is is taking the center portion of the image that would have been cast on a frame of film, and enlarging it more to get to the final print.



the bottom line is, a lens is a lens is a lens.
03-22-2011, 09:33 AM   #3
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What Lowell said!
03-22-2011, 09:37 AM   #4
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QuoteOriginally posted by lguckert79 Quote
so would this efect the apature allso im saying on older lenses like take a 28mm f/2.8 would you take 28mm x 1.5 and then thake the f/2.8 and divided it by 1.5 to get an f/1.8 then???
Short answer: No
Long answer: The 1.5 "crop factor" is only applied to the focal length of the lens. In addition it is ONLY useful for photographers who initially started shooting with 35mm film cameras. Because 35mm film is larger than the sensor in the pentax digital cameras, the field of view is smaller, making the image on it SEEM larger. It actually isn't. In addition the focal length doesn't change either. The only thing that happens is that if you are used to how a 28mm lens performs on a 35mm film camera, the image produced an APC sized sensor will look bigger to you. Approximately the same as if it had been shot with a 44mm lens on a film camera. If you've never shot much with a 35mm film camera you can completely forget about all the "crop factor" BS.

NaCl(hope that helps)H2O

03-22-2011, 09:48 AM   #5
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i started with film in 1995 so this is good to hear from some people about this it helps me understand the difference between the two.
03-22-2011, 10:18 AM - 1 Like   #6
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QuoteOriginally posted by NaClH2O Quote
Short answer: No
Long answer: The 1.5 "crop factor" is only applied to the focal length of the lens. In addition it is ONLY useful for photographers who initially started shooting with 35mm film cameras. Because 35mm film is larger than the sensor in the pentax digital cameras, the field of view is smaller, making the image on it SEEM larger. It actually isn't. In addition the focal length doesn't change either. The only thing that happens is that if you are used to how a 28mm lens performs on a 35mm film camera, the image produced an APC sized sensor will look bigger to you. Approximately the same as if it had been shot with a 44mm lens on a film camera. If you've never shot much with a 35mm film camera you can completely forget about all the "crop factor" BS.

NaCl(hope that helps)H2O

Your explanation is completely accurate. I have only one quibble and a suggestion. In your first sentence, you say the crop factor "is only applied to the focal length of the lens". For those of us who understand the concept of "crop factor", let's all agree that we will refer to it applying to the ANGLE OF VIEW, not the focal length.

Maybe if we start a trend of referring to it this way, the idea of the crop factor will make more sense to newbies, who have been told that their 50mm lens "becomes" a 75mm lens, which we all know is not true.

If you think about it, the term "crop factor" is, in a rather obtuse way, self-explanatory. We don't refer to cropping a lens; we crop an image. That is exactly what the term refers to. If you take a 24 x 36mm image and crop a 24 x 16mm image out of the center, you have an APS-C sized image.
03-22-2011, 10:33 AM   #7
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QuoteOriginally posted by noblepa Quote
Your explanation is completely accurate. I have only one quibble and a suggestion. In your first sentence, you say the crop factor "is only applied to the focal length of the lens". For those of us who understand the concept of "crop factor", let's all agree that we will refer to it applying to the ANGLE OF VIEW, not the focal length.

Maybe if we start a trend of referring to it this way, the idea of the crop factor will make more sense to newbies, who have been told that their 50mm lens "becomes" a 75mm lens, which we all know is not true.

If you think about it, the term "crop factor" is, in a rather obtuse way, self-explanatory. We don't refer to cropping a lens; we crop an image. That is exactly what the term refers to. If you take a 24 x 36mm image and crop a 24 x 16mm image out of the center, you have an APS-C sized image.
Yes to that :-)

A recent poll indicated about 80% of respondents started on 35mm film, so the crop factor indeed is relevant. But yes, it should refer to the angle of view, not the length.
03-22-2011, 10:39 AM   #8
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Paul: I stand corrected. In fact if you read my post, I seem to contradict myself a bit. First I say that it applies to the focal lenght of the lens and then I say the focal lenght doesn't change. I should have said the field of view the focal length generates that would have been more correct.

NaCl(mea culpa...which is a fancy of saying my bad)H2O

03-22-2011, 10:39 AM   #9
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QuoteOriginally posted by SpecialK Quote
Yes to that :-)

A recent poll indicated about 80% of respondents started on 35mm film, so the crop factor indeed is relevant. But yes, it should refer to the angle of view, not the length.
I started on film in 1980 and still (as of last week anyway) shoot both. I never ever think focal length but field of view, or in extreme telephoto shots image size relative to sensor size. Just do a search when people ask about magnification. I always quote:

image size = subject size * focal length / distance

Note here there is no crop factor involved just pure optics
03-22-2011, 10:45 AM   #10
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QuoteOriginally posted by SpecialK Quote
Yes to that :-)

A recent poll indicated about 80% of respondents started on 35mm film, so the crop factor indeed is relevant. But yes, it should refer to the angle of view, not the length.
Is it that high? really? I am astounded. If you had asked me I would have said that 50% or less of the people shooting with DSLRs came from the film world.

NaCl(but what do I know?)H2O
03-22-2011, 11:00 AM   #11
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QuoteOriginally posted by noblepa Quote
Your explanation is completely accurate. I have only one quibble and a suggestion. In your first sentence, you say the crop factor "is only applied to the focal length of the lens". For those of us who understand the concept of "crop factor", let's all agree that we will refer to it applying to the ANGLE OF VIEW, not the focal length.

Maybe if we start a trend of referring to it this way, the idea of the crop factor will make more sense to newbies, who have been told that their 50mm lens "becomes" a 75mm lens, which we all know is not true.

If you think about it, the term "crop factor" is, in a rather obtuse way, self-explanatory. We don't refer to cropping a lens; we crop an image. That is exactly what the term refers to. If you take a 24 x 36mm image and crop a 24 x 16mm image out of the center, you have an APS-C sized image.
APS was around as a "crop" film standard long before digital sensors coalesced on the format:

Advanced Photo System - Wikipedia, the free encyclopedia
03-22-2011, 11:08 AM   #12
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QuoteOriginally posted by Aristophanes Quote
APS was around as a "crop" film standard long before digital sensors coalesced on the format:

Advanced Photo System - Wikipedia, the free encyclopedia
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03-22-2011, 01:27 PM   #13
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QuoteOriginally posted by SpecialK Quote
Yes to that :-)

A recent poll indicated about 80% of respondents started on 35mm film, so the crop factor indeed is relevant. But yes, it should refer to the angle of view, not the length.
I don't place much stock in polls. The "science" in this discipline has devolved into relative meaninglessness in many cases.

If the question was: "Did you own and use a 35mm film SLR or interchangeable lens rangefinder camera at any time before you purchased your DSLR?" then the number could be close to valid. . .

If the question was "Have you used 35mm film for photography in the past?" then I'd question the validity -- anyone that ever used a disposable camera or a P&S film camera would think back and say "yeah". . . and respond positively -- but have no actual reference burned in as to the relationship of FL to FOV.

My personal feeling is that since the great majority of DSLRs are now APS-C format, this should be the current "standard" and FOV on this sensor should be the reference. Then, FL would be FL again, with an implied 24x16 FOV as the standard.

I shot 35mm SLRs from '67 to about '80 and have shot Pentax DSLRs (with tens of thousands more actuations) since '06 to the present. my F1 Original has not had film in it for 30 years and I couldn't mentally reference 35mm FOV to FL other than "normal" "wide" or "tele" to save my life.

Since "APS-C" is a PIA for me to type, I'd also shorten the sensor format description to AD ("D" for digital). Right hand holds the Shift key, A and D only needs the left hand.

This, of course, has little chance of gaining much foothold in the industry. The P&S camera makers constantly reference FL equivalence, and it's in 35mm film terms. The majority of first time DSLR buyers come from the P&S digital world, so the mfgs assume that they will want continuity. . . But that's not necessarily true because many of these users only real reference to FL is the "zoom factor" so they tend to think in terms of 3x, 18x instead of FL or even FL equivalence.

Perhaps we need a law that requires the Marketing Director of the mfg to answer every "crop factor" question that ever appears in any online forum dedicated to their camera make. . .

I assume that the MF digital community doesn't have this problem because the entry fee is high enough that only people with significant photographic background enter into it. . .

Sorry for the rant. . . I couldn't help myself

Scott
03-22-2011, 03:09 PM   #14
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QuoteOriginally posted by NaClH2O Quote
Is it that high? really? I am astounded. If you had asked me I would have said that 50% or less of the people shooting with DSLRs came from the film world.

NaCl(but what do I know?)H2O

Yep. I also say polls should be outlawed, though not because of that one, necessarily.
03-22-2011, 04:49 PM   #15
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QuoteOriginally posted by SpecialK Quote
Yep. I also say polls should be outlawed, though not because of that one, necessarily.
Someone once said given enough data you can prove anything with statistics
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