35mm L lenses on APS-C sensor cameras?

[Rubar]

Hi!

I've been searching around the net to find out what happens if I attach a Canon L series lenses to a APS-C sized sensor cameras. I found several sites with images and lots of information, but did not get a clear answer. I understand the framing difference, but I can’t figure out the thing with numbers.
If I attach for example Canon EF 70-200mm f/4.0 L IS USM lens to my Canon 600D, do I get at maximum zoom the same results as wit Canon EF-S 18-200mm f/3.5-5.6 IS Lens? Or I get with EF 70-200 L lens 200x1.6=320mm which is more zoom than EF-S 18-200 lens?

Thanks in advance!

[Sean Setters]

If you attach a 70-200mm lens to a camera with an APS-C sized sensor, it will have a Full Frame equiv. focal range of 112-320mm. If you attach a 35mm lens to a camera with an APS-C sized sensor, it will have an equiv. focal length of 56mm.

[clemmb]

If you attach a 70-200mm lens to a camera with an APS-C sized sensor, it will have a Full Frame equiv. focal range of 112-320mm. If you attach a 35mm lens to a camera with an APS-C sized sensor, it will have an equiv. focal length of 56mm.

And if you attach an 18-200 to your camera it will have a Full Frame equiv. focal range of 28.8-320mm. The crop factor is 1.6 regardless of whether it is an EF or EF-S lens.

[neuroanatomist]

If I attach for example Canon EF 70-200mm f/4.0 L IS USM lens to my Canon 600D, do I get at maximum zoom the same results as wit Canon EF-S 18-200mm f/3.5-5.6 IS Lens? Or I get with EF 70-200 L lens 200x1.6=320mm which is more zoom than EF-S 18-200 lens?

Focal length is an intrinsic property of the lens, and is a measure of the distance between the rear nodal point of the infinity-focused lens and the focal plane (sensor). Sensor size (APS-C vs. FF) has nothing to do with it and no effect on focal length. The numbers printed on the barrel of the lens are not somehow 'adjusted' for the sensor size, at least with dSLR lenses (some point-and-shoot cameras do have the FF equivalent focal lengths printed on them). What a smaller sensor like APS-C does is only capture a smaller portion of the image circle projected by an EF lens, and EF-S lenses are designed with a smaller image circle (which is why they don't work on FF cameras) to reduce size, weight, and cost.

So, in theory for your example of the EF 70-200mm L lens vs. the EF-S 18-200mm, if you use them both on the same camera, 200mm will give you the same field of view. In practice, there is a difference in this case - the 18-200mm lens doesn't really deliver 200mm at the long end; I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

[clemmb]

I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

Interesting

[HDNitehawk]

. In practice, there is a difference in this case - the 18-200mm lens doesn't really deliver 200mm at the long end; I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

That one is odd. I think I would go back and check the testing methods. Canon could owe allot of people money for false advertising, I wonder what 40mm would be worth in a class action lawsuit

[Daniel Browning]

That one is odd. I think I would go back and check the testing methods. Canon could owe allot of people money for false advertising, I wonder what 40mm would be worth in a class action lawsuit

The 18-200mm *is* 200mm at infinity. I'm sure that Neuro's test was for a much closer focus distance. Focal length can vary with normal manufacturing tolerances, and +/- 5% wouldn't surprise me, but 20% certainly would.

[HDNitehawk]

The 18-200mm *is* 200mm at infinity. I'm sure that Neuro's test was for a much closer focus distance. Focal length can vary with normal manufacturing tolerances, and +/- 5% wouldn't surprise me, but 20% certainly would.

Daniel, I think we are confusing manufacturing tolerances with marketing tolerances. I think within 30% accuracy would be the norm for Canon's marketing accuracy. They just tweaked the numbers so they got a nice even 200

[neuroanatomist]

That one is odd. I think I would go back and check the testing methods. Canon could owe allot of people money for false advertising, I wonder what 40mm would be worth in a class action lawsuit

My testing method was to focus on an object at a reasonable distance (50 feet or so) and take a picture with the 18-200mm at 200mm and the 70-200mm L at 200mm, then overlap them in Photoshop and estimate the relative cropping. It was significant. Bryan notes the same phenomenon in his review of the 18-200mm, and the pics of the starfish seem no different at 170mm vs. 200mm.

It could just be really bad focus breathing, such that anything even a little less than infinity focus results in a much shorter apparent focal length. Most people who buy a 100mm L Macro don't know they're really buying a zoom lens , and at 1:1 magnification the effective focal length is only 80mm. But in the case of the 18-200mm, I wasn't anywhere near a 'macro' distance.

[HDNitehawk]

It was significant. Bryan notes the same phenomenon in his review of the 18-200mm, and the pics of the starfish seem no different at 170mm vs. 200mm.

Wow...this really muddies the answer to Rubar's original question. If you go to Canon's website it says that this lens is the FF equivalent to 29mm-320mm. If what you and Bryan found is true, which I do not doubt what you found, this would really be blatant false advertising. But I guess 18-200mm just sounds and sells better than say a 18-170mm