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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 05 May 2009 (Tuesday) 11:53
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Conflicting info on "crop factor", zoom, etc.

 
Mk1Racer
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May 06, 2009 07:25 |  #46

Jman13 wrote in post #7865328 (external link)
Magnification is simply a reference to the amount of enlargement from either

a) The size of the real object to the size of the object on film/sensor. This is constant regardless of the size of the format, so magnification never changes with format when you are talking about lens magnification. I.e. a 1:1 macro can always do 1:1 on any format. Now, 1:1 on a crop body is a smaller object than 1:1 on a larger sensor, but it's still 1:1...the projected image is life size.

b) Magnification from sensor to print. Obviously, you are enlarging a crop sensor image more than an uncropped full frame image when printing. (I.e....printing an APS-C image at 8x12 inches is magnifying the sensor 13 times...printing a full frame image at 8x12 is magnifying the sensor 8 times.) This is regardless of pixels, as pixels enter no part of the equation. What should tell you this for certain is that there's no standard format for pixel size or density.

Yes, but if all else is equal (lens, distance from subject), you will have a 'larger' image from the FF sensor. To get exactly the same 8x12 image size (i.e. pictures are the exact same, except for the things like IQ, DoF, etc.), you would have to shorten the distance from subject, use a longer lens (zoom in more), or crop the FF image, all by a factor of 1.6. If you hold focal length and distance from subject constant, and crop the FF image to give you the same image 'content', you will magnify that section of the FF sensor 13 times, to get that 8x12 print.

Same with sensor size (and thus the 'full frame equivalent') 35mm is less than a century old. Before that, they still had lenses, and they still had focal lengths. Large format shooters (say, 8x10 view cameras) used 300mm lenses as the normal prime...we now use 50mm on 35mm format and 30mm on APS-C. Why don't we have a 10x crop factor on APS-C, since it's 10x smaller than 8x10? Why? Because there's no need...there is no master format...not now, not ever...which is why there can never be a change to the 'real focal length' based on format....there are TONS of different formats, and they all use lenses of the same focal length...they just look different on each format. When 35mm first started becoming popular, people didn't say that their 50mm lens was really an 80mm lens on 35mm, since it had the same FOV as an 80mm lens on medium format!

Totally agree.

Then, how does the EF-S lens come into play. I've heard these have the 1.6x thing factored in, and they are labeled "correctly" for 1.6x cameras. So, a 250mm EF-S lens is equal to a shorter EF lens?

Simple test, put an EF-S lens on your 30D and shoot a picture. Now take an EF lens @ the same focal length and same distance from subject, and shoot the same picture. The image 'content' will be the same. Things like sharpness, IQ, etc. may be different, but other than that, they'll be the same image. Focal length is focal length. I did this w/ my 40D using my EF-S 17-85 @ 70mm and my EF 70-200 f/4L @ 70mm (both @ f/8) and other than the obvious differences due to lens quality, both images were the same.


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xarqi
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May 06, 2009 07:32 |  #47

Mk1Racer wrote in post #7867173 (external link)
To get exactly the same 8x12 image size (i.e. pictures are the exact same, except for the things like IQ, DoF, etc.), you would have to shorten the distance from subject, use a longer lens (zoom in more), or crop the FF image, all by a factor of 1.6.

Changing distance will change perspective and therefore composition. The picture will not be "the exact same", unless you consider such a change inconsequential enough to be in your "etc."




  
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SkipD
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May 06, 2009 07:49 |  #48

xarqi wrote in post #7867200 (external link)
Changing distance will change perspective and therefore composition. The picture will not be "the exact same", unless you consider such a change inconsequential enough to be in your "etc."

Totally agree. Check out our tutorial on controlling perspective in your images.


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May 06, 2009 08:01 |  #49

HeathNC wrote in post #7865232 (external link)
Still, no one "absolute" answer. Everyone knows the answer, and they are still conflicting. At least it's been entertaining.

There is only one correct answer. The conflict is because someone is still wrong.


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HeathNC
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May 06, 2009 09:06 |  #50

Thanks guys. This was not only informative, but entertaining.


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Mk1Racer
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May 06, 2009 09:12 |  #51

xarqi and Skip,

Thanks for correcting me, I had forgotten to consider the perspective aspect of it. You guys are indeed correct. Thanks again for pointing out my error.


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slkfis
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May 06, 2009 09:30 as a reply to  @ Mk1Racer's post |  #52

As a rookie I to was confused on the FF vs 1.6 zoom lens and had actually been doing calculations as I reviewed potential lens purchases.

This thread has got me on the right track.

I found the easiest definition was to take a photo (40D) go to PP and crop it to the center.

Well lo and behold a simulated crop sensor! I think!

I certainly appreciate the sharing of knowledge, most obviously learned from experience, the people on this site will share. Maybe someday I'll have enought to share.

thxs

slkfis :cool:

Bob


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Mk1Racer
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May 06, 2009 09:33 |  #53

slkfis wrote in post #7867802 (external link)
As a rookie I to was confused on the FF vs 1.6 zoom lens and had actually been doing calculations as I reviewed potential lens purchases.

This thread has got me on the right track.

I found the easiest definition was to take a photo (40D) go to PP and crop it to the center.

Well lo and behold a simulated crop sensor! I think!

I certainly appreciate the sharing of knowledge, most obviously learned from experience, the people on this site will share. Maybe someday I'll have enought to share.

thxs

slkfis :cool:

Bob


Bob, you've essentially double-cropped that picture (compared to a FF body). What you would need to do, is shoot that photo w/ a 5D or a 1D and then crop it, to simulate what you'd get out of the xxxD or xxD bodies.


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Marius ­ B
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May 06, 2009 09:42 |  #54

One question:
I use both my 5D and my 40D, when I was at the track the other day, I changed from 5D to 40D with my 70-200 to "zoom" closer. Are you guys saying that I could have taken the picture with my 5D and cropped it and got a better or equal result?

I think of it as changing camera is like original zoom, but cropping in PP is like digital zoom.. I have never compared these different approaches.


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May 06, 2009 09:53 |  #55

Marius B wrote in post #7867869 (external link)
One question:
I use both my 5D and my 40D, when I was at the track the other day, I changed from 5D to 40D with my 70-200 to "zoom" closer. Are you guys saying that I could have taken the picture with my 5D and cropped it and got a better or equal result?

I think of it as changing camera is like original zoom, but cropping in PP is like digital zoom.. I have never compared these different approaches.

Yes, assuming that the pixel density (how many in a square millimeter) was identical, then [Shoot FF and crop] = [Shooting APS-C]

In the past, APS-C pixel density was often higher than the 5D, leading to the so-called 'reach advantage'. Compare the same camera's APS-C pixel density to a 5DII, that 'advantage' of APS-C well might disappear! For example, 5D has 121 pixels/mm, 30D has 155, 5DII has 156. Comparing the current APS-C to the current FF, there is even higher pixel density for th 40D and 50D.

So reach advantage 30D vs. 5D, no reach advantage 30D vs. 5DII. Reach advantage once again, 40D/50D vs 5DII.


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MikeES
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May 06, 2009 10:07 |  #56

Wilt wrote in post #7867943 (external link)
Yes, assuming that the pixel density (how many in a square millimeter) was identical, then [Shoot FF and crop] = [Shooting APS-C]

In the past, APS-C pixel density was often higher than the 5D, leading to the so-called 'reach advantage'. Compare the same camera's APS-C pixel density to a 5DII, that 'advantage' of APS-C well might disappear! For example, 5D has 121 pixels/mm, 30D has 155, 5DII has 156. Comparing the current APS-C to the current FF, there is even higher pixel density for th 40D and 50D.

So reach advantage 30D vs. 5D, no reach advantage 30D vs. 5DII. Reach advantage once again, 40D/50D vs 5DII.

This assumes that all pixels were created equal. I was under the impression that larger pixels create better pictures...is that way off base?


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Marius ­ B
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May 06, 2009 10:26 |  #57

Wilt wrote in post #7867943 (external link)
Yes, assuming that the pixel density (how many in a square millimeter) was identical, then [Shoot FF and crop] = [Shooting APS-C]

In the past, APS-C pixel density was often higher than the 5D, leading to the so-called 'reach advantage'. Compare the same camera's APS-C pixel density to a 5DII, that 'advantage' of APS-C well might disappear! For example, 5D has 121 pixels/mm, 30D has 155, 5DII has 156. Comparing the current APS-C to the current FF, there is even higher pixel density for th 40D and 50D.

So reach advantage 30D vs. 5D, no reach advantage 30D vs. 5DII. Reach advantage once again, 40D/50D vs 5DII.

Thanks, didn't know the numbers of pixel/mm. So then there is a reason for me to use the 40D for longer reach/reach advantage.


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May 06, 2009 10:32 |  #58

SkipD wrote in post #7863091 (external link)
Focal length is focal length, period.

It doesn't get any simpler than that.

Thanks for your post, Skip. Hopefully it'll educate those who are misinformed.


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May 06, 2009 10:36 |  #59

MikeES wrote in post #7868034 (external link)
This assumes that all pixels were created equal. I was under the impression that larger pixels create better pictures...is that way off base?

Not off base...larger pixel produces less noise. However, the processing can nullify that. Witness the smaller pixel of 50D vs. 40D, yet 50D processing is better at reducing noise, so that noise content of the final print is about the same.

Problem is that IQ is 'resolution' and 'noise', not merely one not the other. 'Reach advantage' only addresses resolution advantage, ignores noise disadvantage.


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May 06, 2009 12:22 |  #60

cwphoto wrote in post #7867338 (external link)
There is only one correct answer. The conflict is because someone is still wrong.

Can't fault the logic!


Mark.

  
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