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03-22-2011, 05:47 PM   #16
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If I take 3 pictures and get std 6x4 prints, which two look the most alike?

Pic 1 : 35mm film camera using a 50mm lens
Pic 2 : APS-C dSLR using a 50mm lens
Pic 3 : 35mm film camera using a 75mm lens

?

03-22-2011, 06:46 PM   #17
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QuoteOriginally posted by HGMonaro Quote
If I take 3 pictures and get std 6x4 prints, which two look the most alike?

Pic 1 : 35mm film camera using a 50mm lens
Pic 2 : APS-C dSLR using a 50mm lens
Pic 3 : 35mm film camera using a 75mm lens

?
If the three photos are of me, my dog, and my cat, none will look alike. I hope.

If you mean, three photos taken from the same place of the same subject at the same distance with the same settings, the answer is the same: none of them.

If you mean, three photos taken of the same subject with the same settings, but with the camera moved to equally fill the frame with the subject, the answer is: (2) and (3). They will look *most* alike, except that perspective and background and other characteristics will be different.

These are apples vs oranges.

BTW, my dog and cat have both died. Please don't dig them up. Icky...
03-22-2011, 07:01 PM   #18
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QuoteOriginally posted by HGMonaro Quote
If I take 3 pictures and get std 6x4 prints, which two look the most alike?

Pic 1 : 35mm film camera using a 50mm lens
Pic 2 : APS-C dSLR using a 50mm lens
Pic 3 : 35mm film camera using a 75mm lens

?
2 and 3. (1 and 3 use the same body, one with standard and the other with a short telephoto lens).
03-22-2011, 09:18 PM   #19
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BTW, this little quiz is meant to emphasise from the point of view of the newbie looking at images as taken in camera (no PP cropping), hence the question including the word 'most'. They might not notice (or care about) the relationship between background and foreground objects, etc, they just want to get the object of their photographic desire in the picture... and thus 'you' can parrot on about a 50mm lens is a 50mm lens all day long but stick it on a camera with a different sized imaging device, and it does make a difference to the end result, and why this question will keep being asked regardless of the existance of search engines.

03-22-2011, 09:51 PM   #20
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QuoteOriginally posted by HGMonaro Quote
They might not notice (or care about) the relationship between background and foreground objects, etc, they just want to get the object of their photographic desire in the picture...
In that case, the answer is 1+2+3. All can make a frame-filling subject look rather the same, if the camera is in different positions for each shot, and if everything but the subject is ignored. Given your parms, format doesn't matter. Focal length doesn't matter. Nothing matters but EV. I could use 110 / m4/3, APS-C / 135/HF, 135/FF, 645, 6x9, and tiny P&S cams with various lenses of various focal lengths at various distances with various settings, and get shots where the subject looks essentially the same when printed small. BFD. Calling those 'equivalent' is just wrong. As in, it ain't so.
03-23-2011, 01:00 AM   #21
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cite your source

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 dont actually believe those numbers, can you cite your source so we can judge it for accuracy.

I also believe the original post was a troll, or where I come from its know as sh1t-stirring, YMMV
03-23-2011, 01:09 AM   #22
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simple

For those like me, who did come from a 35mm background, the change was simple.

I originally regarded 50mm as a "standard" lens, anything above was more or less telephoto, anything less was more or less wide-angle. Now I regard 35mm as the "standard". That's the sum total of my mind-change.

I also get to use my 24mm lens more, as it now gives me the FOV I favour for the majority of wild mountain landscapes. AND I have a great short fast tele for portrait work with the 50mm 1.4

Why do we always respond with a full blown dissertation whenever the "crop factor" is mentioned. Move on please.
03-23-2011, 04:37 AM   #23
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QuoteOriginally posted by RioRico Quote
In that case, the answer is 1+2+3. All can make a frame-filling subject look rather the same, if the camera is in different positions for each shot, and if everything but the subject is ignored. Given your parms, format doesn't matter. Focal length doesn't matter. Nothing matters but EV. I could use 110 / m4/3, APS-C / 135/HF, 135/FF, 645, 6x9, and tiny P&S cams with various lenses of various focal lengths at various distances with various settings, and get shots where the subject looks essentially the same when printed small. BFD. Calling those 'equivalent' is just wrong. As in, it ain't so.
but you're assuming you can move to obtain that similar subject size. That's not always possible. Why do manufacturers supply 18-55 kit lenses and not 28-75's?

03-23-2011, 05:57 AM   #24
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QuoteOriginally posted by Lowell Goudge Quote
Someone once said given enough data you can prove anything with statistics
There are lies, damn lies, and statistics. I've heard that more than once from multiple sources.
03-23-2011, 06:06 AM   #25
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QuoteOriginally posted by NaClH2O Quote
In addition it is ONLY useful for photographers who initially started shooting with 35mm film cameras.
That's not quite true — if that were the only use, it probably wouldn't have gotten so much traction. It's also useful for comparing field of view between sensor formats — our 1.5×, Olympus's 2×, Canon's 1.6× and 1.3×, and of course full 35mm frame.

Oh, and with the 645D, for that matter.
03-23-2011, 08:20 AM   #26
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QuoteOriginally posted by keithlester Quote
I dont actually believe those numbers, can you cite your source so we can judge it for accuracy.

I also believe the original post was a troll, or where I come from its know as sh1t-stirring, YMMV
It was a poll on the forum, a few months back. You can dredge it up.

It's a public poll, so it is not accurate.
03-24-2011, 03:27 AM   #27
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QuoteOriginally posted by NaClH2O Quote
Long answer: The 1.5 "crop factor" is only applied to the focal length of the lens...
That's not correct. When a conversion factor is applied, it has to be applied to both focal length and f-ratio.

Of course, the optical properties of a lens don't change when switched from one camera to another with a smaller sensor. But the FOV changes. Since photographers don't express the field of view of a lens in FOV degrees but in terms of focal length and the 35mm standard has been a common standard for a long time, it makes sense to express the new FOV in terms of the old 35mm format as an equivalent focal length.

The equivalent focal length, i.e., it is a hypothetical focal length, not a real one, of a 50mm lens on APS-C is 75mm (assuming a 1.5 crop factor). In other words, a 35mm camera with a 75mm lens would produce the same image as the APS-C camera with a 50mm lens (camera position unchanged). But only if one also converts the f-ratio. If the 50mm lens on APS-C is set to f/1.4 then the 75mm lens on the 35mm camera must be set to f/2.1. Only then both cameras will produce the same image with the same DOF.

Therefore, the 35mm-equivalent lens of a 50/1.4 on APS-C is a 75/2.1. In other words, if the crop factor is used to calculate equivalent properties then not only the focal length has to be converted, but the f-ratio as well.

One easy way to think about this is to imagine how one could reproduce the image projected on an APS-C sensor on a 35mm-sized sensor. The device that does exactly this, is a 1.5x teleconverter. As we all know, teleconverters do not only convert focal length, but also f-ratios.

Hope that helps.

QuoteOriginally posted by HGMonaro Quote
If I take 3 pictures and get std 6x4 prints, which two look the most alike?

Pic 1 : 35mm film camera using a 50mm lens
Pic 2 : APS-C dSLR using a 50mm lens
Pic 3 : 35mm film camera using a 75mm lens

?
Assuming the camera position is not changed (doing so would change perspective and thus create different images), 2 & 3 as long as the 75mm lens is set to an f-ratio that is 1.5 x the f-ratio setting on the 50mm lens.

QuoteOriginally posted by bimjo Quote
There are lies, damn lies, and statistics.
Statistics can only be lies if the reader doesn't see the potential manipulation. There are mathematical laws as to what can be concluded from a number of events and what not (-> statistical significance). If the numbers don't allow the conclusions claimed then someone just lies; nothing to do with statistics.

Last edited by Class A; 03-24-2011 at 03:38 AM.
03-24-2011, 04:44 AM   #28
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ClassA. Your answer is unfortunately very misleading. Go back to basics. Any lens when used to take a picture from the same place at the same magnification will produce the exact same perspective regardless of the crop factor. Just try a simple test. Take one shot and print 2 copies of it on a full page. Now cut the middle 60% out of one copy and copmare it to the second. Did anything change NO.

Now move in using a shorter lens and take a shot framing the image on an ASP-C sensor to match your original image and print to the same size. All sorts of things change because you have moved and you have also in erased the image enlargement by 50%.

So forget all this BS about crop factor and simply consider how the lens performs on digital. Also the crop factor is not relevant to someone coming from film but only to someone shooting multiple formats at the same time. I shoot both and I don't care at all about crop factor. I concern myself with magnification ratio or projected subject size when looking at telephoto lenses and field of view with wide angle shots. It's that simple
03-24-2011, 01:26 PM   #29
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QuoteOriginally posted by Lowell Goudge Quote
ClassA. Your answer is unfortunately very misleading.
Lowell, I don't think so. I think that stating that "crop factors are BS" is misleading. Say you have been shooting with a 50mm lens on 35mm film almost all your life. Now someone gives you a digital Canon camera with a 1.3 crop factor. How do you work out what focal length you need on the new camera to replicate the 50mm on 35mm film FOV, you've been using all your life? Use the crop factor to calculate the equivalent lens parameters and you are done. I find that useful because it works for all sorts of funny formats you find in the film world.

QuoteOriginally posted by Lowell Goudge Quote
Any lens when used to take a picture from the same place at the same magnification will produce the exact same perspective regardless of the crop factor.
I have never said anything to the contrary.

QuoteOriginally posted by Lowell Goudge Quote
Just try a simple test. Take one shot and print 2 copies of it on a full page. Now cut the middle 60% out of one copy and copmare it to the second. Did anything change NO.
If this test has to do with an APS-C vs FF comparison, note that one would typically print to the same size so the inner 60% would appear enlarged to the 100% size (reducing the DOF), and this -- unlike your experiment -- changes quite a lot. Also note, that someone having the inner 60% only (e.g., an APS-C shooter) does not have the outer 40%. So yes, while making the sensor smaller doesn't change anything to the image captured by both smaller and larger sensor, there are still important differences regarding a final image.

QuoteOriginally posted by Lowell Goudge Quote
Now move in using a shorter lens and take a shot framing the image on an ASP-C sensor to match your original image and print to the same size. All sorts of things change because you have moved and you have also in erased the image enlargement by 50%.
We agree. I said you must not move the camera, otherwise the perspective changes and you'll never get "alike" images.

Please read my post again. To get an equivalent image, you must not change the camera position. If you change the sensor format, you have to change both focal length and f-ratio to get the same image. Are you disputing that? If not, what is wrong about letting people do the math about what settings they need?

Say someone wants to replicate a famous Ansel Adam shot. If they know the focal length, f-ratio (and potentially shutter speed) Adams used, then -- by doing a format conversion involving a crop factor -- they can work out which focal length, f-ratio to use on APS-C.

My "misleading" explanation would allow me to replicate the shot.

How would you replicate the shot without using a "BS crop factor"?

QuoteOriginally posted by Lowell Goudge Quote
So forget all this BS about crop factor and simply consider how the lens performs on digital.
A crop factor calculation allows me to know how a lens will perform on digital without trying it. I find a "consideration" that is based on "knowing (in terms of FF parameters" better than one that must rely on doing test shots.

QuoteOriginally posted by Lowell Goudge Quote
I shoot both and I don't care at all about crop factor.
Good for you, but there is no need to call a perfectly clear explanation that may be useful to some "misleading".

QuoteOriginally posted by Lowell Goudge Quote
I concern myself with magnification ratio or projected subject size when looking at telephoto lenses and field of view with wide angle shots. It's that simple
To be honest, I don't find that particularly useful myself, but to each their own. I'm fine for you to use whatever approach you like, but I kindly ask you to not label my explanation as "misleading".

Last edited by Class A; 03-24-2011 at 01:33 PM.
03-24-2011, 01:40 PM   #30
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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???
The 28mm/2.8 lens doesn't change its physical properties when you mount it on an APS-C camera.

What the crop factor allows you to do is to
  1. work out what lens you'd need on a full-frame camera to replicate the look a 28/2.8 lens produces on APS-C (-> 42 mm f/4.2)
  2. work out what lens you need on APS-C to replicate the look a 28/2.8 lens produces on an FF camera (-> 19mm f/1.9)
Hope that helps and sorry that I didn't answer it like that straight away.
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