focal length

Wheatfield · 03-23-2010, 05:22 AM

There is no such thing as crop factor. A 70/2.4 lens is a 70/2.4 lens, not matter what format is put behind it.

enoeske · 03-23-2010, 06:04 AM

Originally posted by Wheatfield

There is no such thing as crop factor. A 70/2.4 lens is a 70/2.4 lens, not matter what format is put behind it.

There is such a thing as crop factor. We aren't discussing the lens itself (which doesn't change) but the image that lens projects onto differing sized sensors such as APS-C and 35mm FF.

landscaped1 · 03-23-2010, 08:16 AM

Thanks to everyone for clearing that up. I feel better now!

sjwoo · 03-23-2010, 08:27 AM

I've seen in some reviews where they say that the 55-300mm Pentax kit lens is equivalent to 82-450mm, because of the 1.5x multiplier. Is this just marketing mumbo-jumbo, or is it actually true? From reading this thread, it seems as if 55-300mm is 55-300mm, a rose is a rose is a rose...

RioRico · 03-23-2010, 09:08 AM

Originally posted by sjwoo

I've seen in some reviews where they say that the 55-300mm Pentax kit lens is equivalent to 82-450mm, because of the 1.5x multiplier. Is this just marketing mumbo-jumbo, or is it actually true? From reading this thread, it seems as if 55-300mm is 55-300mm, a rose is a rose is a rose...

The rose IS the rose, and is ONLY the rose, but sometimes it looks like a BIGGER rose. Or something like that.

Look, crop factor or multiplier ONLY applies when you want to compare what a lens see on full-frame, with what it sees on APS-C or m4:3 or 110 or some other smaller frame. That's all -- it's a comparison. For people who are used to thinking in full-frame 35mm (35/FF) film terms, it's meaningful. It says, "A 300mm lens on APS-C has the same FOV as a 450mm lens on 35/FF." If you don't think like a film dinosaur (like me), FORGET YOU EVER HEARD OF CROP FACTOR!!

sjwoo · 03-23-2010, 09:14 AM

Originally posted by RioRico

The rose IS the rose, and is ONLY the rose, but sometimes it looks like a BIGGER rose. Or something like that.

Look, crop factor or multiplier ONLY applies when you want to compare what a lens see on full-frame, with what it sees on APS-C or m4:3 or 110 or some other smaller frame. That's all -- it's a comparison. For people who are used to thinking in full-frame 35mm (35/FF) film terms, it's meaningful. It says, "A 300mm lens on APS-C has the same FOV as a 450mm lens on 35/FF." If you don't think like a film dinosaur (like me), FORGET YOU EVER HEARD OF CROP FACTOR!!

What is this "film" thing you're referring to?

Thanks for clearing this up once and for all. I've always considered magnification a better descriptor for a zoom lens than the mm's...

RioRico · 03-23-2010, 09:48 AM

Originally posted by sjwoo

What is this "film" thing you're referring to?

In days of yore
When folks were poor
And baked pots in a kiln
George Eastman dried
A soupy goop
And called it Kodak film.

Don't get me started on early emulsions. I'm an emulsion freak. BACK TO ACTINIC LIGHT!! BACK TO 1880!! FORWARD, INTO THE PAST!

landscaped1 · 03-23-2010, 10:07 AM

Quote:

If you don't think like a film dinosaur (like me), FORGET YOU EVER HEARD OF CROP FACTOR!!

This is where I was getting thrown off. Trying to make comparisons that need not be made.

Wheatfield · 03-23-2010, 12:35 PM

Originally posted by enoeske

There is such a thing as crop factor. We aren't discussing the lens itself (which doesn't change) but the image that lens projects onto differing sized sensors such as APS-C and 35mm FF.

It's interesting that this term didn't come into existence until DSLR cameras.
I never, in all my years of discussing photography at the club level or pro level, had a discussion about crop factor.
We just learned what our lenses did on the format we were using them on rather than on a format that we were not using.
Considering the % of people shooting both film and digital is very small, the sideways thinking where one compares apples to grape nuts is kind of absurd.
People who have never picked up a film SLR in their lives discuss crop factor, even though it is a term with absolutely no frame of reference to them.

enoeske · 03-23-2010, 12:40 PM

Originally posted by Wheatfield

It's interesting that this term didn't come into existence until DSLR cameras.
I never, in all my years of discussing photography at the club level or pro level, had a discussion about crop factor.

Probably because you probably didn't compare image circles from the same lenses on large, medium and 35mm film. This topic comes up in the now because we are using film lenses made for 35mm size film on digital sensors smaller than that format.

RioRico · 03-23-2010, 01:08 PM

Originally posted by enoeske

Probably because you probably didn't compare image circles from the same lenses on large, medium and 35mm film. This topic comes up in the now because we are using film lenses made for 35mm size film on digital sensors smaller than that format.

AFAIK many of the same lenses could be and were used on 4x5", 5x7", 8x10", and other large format cameras. Similarly with the different MF aspects: 645, 6x6, 6x7, 6x9. Not to mention the 6x9 and Polaroid backs used on some LF frames. I don't think crap foctors were discussed in those contexts, maybe because lenses for these were never mass-market items.

I *am* familiar with FF vs HF (half-frame), as I had a Olympus Pen-FT and several Canon half-frames, and I don't recall the term "crop factor" appearing in print (Half-frame 35mm is the same area as APS-C.) The Oly Pen-F series had adapters for M42, T-mount, and the various name-brand bayonets. Half-frame users just knew that FOV was tighter and composed accordingly. I never thought, "Oh, this 200mm is really 300mm! Wow!" Just, "That's a pretty narrow FOV."

OK, it's time to dig up the etymology of crop factor. Any volunteers?

Myltlpny · 03-31-2010, 05:58 AM

This is a very timely thread. I was just working out the same issues. I had read in several places confusing articles regarding focal length and crop factors and they just didn't seem to make sense to me; the inference seemed to indicate greater magnification.
As a bit of an experiment, I pulled out my old ME Super with a 1.4 50mm lens, and compared it to my K100D and KX, with a 1.4 FA 50mm, and my DA 18-55 set at 50mm. I swapped lenses around to all cameras and the only difference was the field of view. Magnification was the same for all three cameras, irregardless of the lens used, which is what I would have expected.

Ira · 03-31-2010, 06:56 AM

Originally posted by Myltlpny

This is a very timely thread. I was just working out the same issues. I had read in several places confusing articles regarding focal length and crop factors and they just didn't seem to make sense to me; the inference seemed to indicate greater magnification.
As a bit of an experiment, I pulled out my old ME Super with a 1.4 50mm lens, and compared it to my K100D and KX, with a 1.4 FA 50mm, and my DA 18-55 set at 50mm. I swapped lenses around to all cameras and the only difference was the field of view. Magnification was the same for all three cameras, irregardless of the lens used, which is what I would have expected.

And different viewfinders magnify differently.

flyer · 03-31-2010, 06:59 AM

Originally posted by landscaped1

The "crop factor" and FOV is what I was having trouble wrapping my head around.

You should forget all that crap about "crop factor" and just get use to what you get with a given lens on your camera. It's a lot easier to work that way. On an APS-C sensor, the normal lens is more or less 30 mm. Anything shorter is wide, and anything longer is tele. Case solved.

noblepa · 03-31-2010, 07:32 AM

Originally posted by flyer

You should forget all that crap about "crop factor" and just get use to what you get with a given lens on your camera. It's a lot easier to work that way. On an APS-C sensor, the normal lens is more or less 30 mm. Anything shorter is wide, and anything longer is tele. Case solved.

Absolutely!

As a long-time 35mm film user, I spent about five minutes thinking about crop factors, when I got my K10D. Then I realized that it didn't matter. As you say, you just need to learn a couple of reference points: 30-35 is "normal", less than 30 is wide, longer than 35 is tele, greater than 200 is long tele.

The same thing happened back in the seventies, when there was a push to switch to the metric system (which has been the official standard in the US since 1870, BTW). Insurance agents and everyone else were giving away english-metric converters, instead of calendars. This led people to believe that they needed to know how to convert from miles to kilometers, or from gallons to liters. You don't. You just need to learn that the speed limit is 100kph, instead of 65mph. You need to learn that your morning commute is 32 kilometers, rather than 20 miles. Comfortable room temperature is 20C, rather than 70F. This perceived math requirement may be one reason that it never caught on.

The only time that crop factor might be an issue is if you regularly switch between 35mm film (or FF dslr) and an aps-c dslr. Even then, only the reference points change. On FF, 50mm is "normal", less than that is wide, more than that is tele.

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03-23-2010, 05:22 AM	#16
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,975	There is no such thing as crop factor. A 70/2.4 lens is a 70/2.4 lens, not matter what format is put behind it.

03-23-2010, 06:04 AM	#17
enoeske Veteran Member Join Date: Jul 2009 Location: Surprise, Az Photos: Gallery Posts: 2,136	Originally posted by Wheatfield There is no such thing as crop factor. A 70/2.4 lens is a 70/2.4 lens, not matter what format is put behind it. There is such a thing as crop factor. We aren't discussing the lens itself (which doesn't change) but the image that lens projects onto differing sized sensors such as APS-C and 35mm FF.

03-23-2010, 08:16 AM	#18
landscaped1 Senior Member Join Date: Jan 2010 Location: Louisiana Photos: Gallery Posts: 153 Original Poster	Thanks to everyone for clearing that up. I feel better now!

03-23-2010, 08:27 AM	#19
sjwoo Forum Member Join Date: Mar 2010 Photos: Albums Posts: 70	I've seen in some reviews where they say that the 55-300mm Pentax kit lens is equivalent to 82-450mm, because of the 1.5x multiplier. Is this just marketing mumbo-jumbo, or is it actually true? From reading this thread, it seems as if 55-300mm is 55-300mm, a rose is a rose is a rose...

03-23-2010, 09:08 AM	#20
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Originally posted by sjwoo I've seen in some reviews where they say that the 55-300mm Pentax kit lens is equivalent to 82-450mm, because of the 1.5x multiplier. Is this just marketing mumbo-jumbo, or is it actually true? From reading this thread, it seems as if 55-300mm is 55-300mm, a rose is a rose is a rose... The rose IS the rose, and is ONLY the rose, but sometimes it looks like a BIGGER rose. Or something like that. Look, crop factor or multiplier ONLY applies when you want to compare what a lens see on full-frame, with what it sees on APS-C or m4:3 or 110 or some other smaller frame. That's all -- it's a comparison. For people who are used to thinking in full-frame 35mm (35/FF) film terms, it's meaningful. It says, "A 300mm lens on APS-C has the same FOV as a 450mm lens on 35/FF." If you don't think like a film dinosaur (like me), FORGET YOU EVER HEARD OF CROP FACTOR!!

03-23-2010, 09:14 AM	#21
sjwoo Forum Member Join Date: Mar 2010 Photos: Albums Posts: 70	Originally posted by RioRico The rose IS the rose, and is ONLY the rose, but sometimes it looks like a BIGGER rose. Or something like that. Look, crop factor or multiplier ONLY applies when you want to compare what a lens see on full-frame, with what it sees on APS-C or m4:3 or 110 or some other smaller frame. That's all -- it's a comparison. For people who are used to thinking in full-frame 35mm (35/FF) film terms, it's meaningful. It says, "A 300mm lens on APS-C has the same FOV as a 450mm lens on 35/FF." If you don't think like a film dinosaur (like me), FORGET YOU EVER HEARD OF CROP FACTOR!! What is this "film" thing you're referring to? Thanks for clearing this up once and for all. I've always considered magnification a better descriptor for a zoom lens than the mm's...

03-23-2010, 09:48 AM	#22
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Originally posted by sjwoo What is this "film" thing you're referring to? In days of yore When folks were poor And baked pots in a kiln George Eastman dried A soupy goop And called it Kodak film. Don't get me started on early emulsions. I'm an emulsion freak. BACK TO ACTINIC LIGHT!! BACK TO 1880!! FORWARD, INTO THE PAST!

03-23-2010, 10:07 AM	#23
landscaped1 Senior Member Join Date: Jan 2010 Location: Louisiana Photos: Gallery Posts: 153 Original Poster	Quote: If you don't think like a film dinosaur (like me), FORGET YOU EVER HEARD OF CROP FACTOR!! This is where I was getting thrown off. Trying to make comparisons that need not be made.

03-23-2010, 12:35 PM	#24
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,975	Originally posted by enoeske There is such a thing as crop factor. We aren't discussing the lens itself (which doesn't change) but the image that lens projects onto differing sized sensors such as APS-C and 35mm FF. It's interesting that this term didn't come into existence until DSLR cameras. I never, in all my years of discussing photography at the club level or pro level, had a discussion about crop factor. We just learned what our lenses did on the format we were using them on rather than on a format that we were not using. Considering the % of people shooting both film and digital is very small, the sideways thinking where one compares apples to grape nuts is kind of absurd. People who have never picked up a film SLR in their lives discuss crop factor, even though it is a term with absolutely no frame of reference to them.

03-23-2010, 12:40 PM	#25
enoeske Veteran Member Join Date: Jul 2009 Location: Surprise, Az Photos: Gallery Posts: 2,136	Originally posted by Wheatfield It's interesting that this term didn't come into existence until DSLR cameras. I never, in all my years of discussing photography at the club level or pro level, had a discussion about crop factor. Probably because you probably didn't compare image circles from the same lenses on large, medium and 35mm film. This topic comes up in the now because we are using film lenses made for 35mm size film on digital sensors smaller than that format.

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03-23-2010, 01:08 PM	#26
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Originally posted by enoeske Probably because you probably didn't compare image circles from the same lenses on large, medium and 35mm film. This topic comes up in the now because we are using film lenses made for 35mm size film on digital sensors smaller than that format. AFAIK many of the same lenses could be and were used on 4x5", 5x7", 8x10", and other large format cameras. Similarly with the different MF aspects: 645, 6x6, 6x7, 6x9. Not to mention the 6x9 and Polaroid backs used on some LF frames. I don't think crap foctors were discussed in those contexts, maybe because lenses for these were never mass-market items. I am familiar with FF vs HF (half-frame), as I had a Olympus Pen-FT and several Canon half-frames, and I don't recall the term "crop factor" appearing in print (Half-frame 35mm is the same area as APS-C.) The Oly Pen-F series had adapters for M42, T-mount, and the various name-brand bayonets. Half-frame users just knew that FOV was tighter and composed accordingly. I never thought, "Oh, this 200mm is really 300mm! Wow!" Just, "That's a pretty narrow FOV." OK, it's time to dig up the etymology of crop factor. Any volunteers?

03-31-2010, 05:58 AM	#27
Myltlpny Inactive Account Join Date: Oct 2007 Location: Gloucester, VA Photos: Gallery Posts: 27	This is a very timely thread. I was just working out the same issues. I had read in several places confusing articles regarding focal length and crop factors and they just didn't seem to make sense to me; the inference seemed to indicate greater magnification. As a bit of an experiment, I pulled out my old ME Super with a 1.4 50mm lens, and compared it to my K100D and KX, with a 1.4 FA 50mm, and my DA 18-55 set at 50mm. I swapped lenses around to all cameras and the only difference was the field of view. Magnification was the same for all three cameras, irregardless of the lens used, which is what I would have expected.

03-31-2010, 06:56 AM	#28
Ira Inactive Account Join Date: Mar 2009 Location: Coral Springs, FL Photos: Gallery \| Albums Posts: 5,216	Originally posted by Myltlpny This is a very timely thread. I was just working out the same issues. I had read in several places confusing articles regarding focal length and crop factors and they just didn't seem to make sense to me; the inference seemed to indicate greater magnification. As a bit of an experiment, I pulled out my old ME Super with a 1.4 50mm lens, and compared it to my K100D and KX, with a 1.4 FA 50mm, and my DA 18-55 set at 50mm. I swapped lenses around to all cameras and the only difference was the field of view. Magnification was the same for all three cameras, irregardless of the lens used, which is what I would have expected. And different viewfinders magnify differently.

03-31-2010, 06:59 AM	#29
flyer Veteran Member Join Date: Jan 2008 Location: Ste-Anne des Plaines, Qc., Canada Posts: 2,013	Originally posted by landscaped1 The "crop factor" and FOV is what I was having trouble wrapping my head around. You should forget all that crap about "crop factor" and just get use to what you get with a given lens on your camera. It's a lot easier to work that way. On an APS-C sensor, the normal lens is more or less 30 mm. Anything shorter is wide, and anything longer is tele. Case solved.

03-31-2010, 07:32 AM	#30
noblepa Veteran Member Join Date: Sep 2007 Location: Bay Village, Ohio USA Posts: 1,142	Originally posted by flyer You should forget all that crap about "crop factor" and just get use to what you get with a given lens on your camera. It's a lot easier to work that way. On an APS-C sensor, the normal lens is more or less 30 mm. Anything shorter is wide, and anything longer is tele. Case solved. Absolutely! As a long-time 35mm film user, I spent about five minutes thinking about crop factors, when I got my K10D. Then I realized that it didn't matter. As you say, you just need to learn a couple of reference points: 30-35 is "normal", less than 30 is wide, longer than 35 is tele, greater than 200 is long tele. The same thing happened back in the seventies, when there was a push to switch to the metric system (which has been the official standard in the US since 1870, BTW). Insurance agents and everyone else were giving away english-metric converters, instead of calendars. This led people to believe that they needed to know how to convert from miles to kilometers, or from gallons to liters. You don't. You just need to learn that the speed limit is 100kph, instead of 65mph. You need to learn that your morning commute is 32 kilometers, rather than 20 miles. Comfortable room temperature is 20C, rather than 70F. This perceived math requirement may be one reason that it never caught on. The only time that crop factor might be an issue is if you regularly switch between 35mm film (or FF dslr) and an aps-c dslr. Even then, only the reference points change. On FF, 50mm is "normal", less than that is wide, more than that is tele.