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I have a Canon EF 100mm Macro and a Canon EF-S 18-200mm Lens, and using a Canon EOS 60D.

I believed that when setting the Zoom Lens to 100mm it would show the same field of view as the one from Macro.

Turns that I was wrong. Even putting the Zoom Lens to 200mm, the field of view from the Macro Lens is "closer". But why is that?

I tried to google and just read that there should not be any differences between the EF and the EF-S model regarding the crop factor.

Here the two pictures in question (both taken from tripod):

Image 1 - 100mm Macro Lens - Exif <-- It's more zoomed in than Image 2

Image 2 - 200mm Zoom Lens - Exif

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Regarding your examples: try the same thing outdoors; shoot something that is far from the camera and you will see that you get the same field-of-view. (It gets much trickier at macro distances.) – Jukka Suomela Oct 8 '11 at 9:06
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Is the camera fixed on a tripod, or are you moving each lens to focus, as the macro will be able to get closer and make the object larger? – Dreamager Oct 8 '11 at 10:12
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Actually, it is not the location of the camera that matters, it is the location of the center of perspective that matters. If you keep the location of the camera fixed and change lenses, in most cases you will actually move the center of perspective slightly. That's one reason why it is tricky to compare field-of-view at macro distances. See also en.wikipedia.org/wiki/Entrance_pupil – Jukka Suomela Oct 8 '11 at 18:00
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@gsharp: I think we need more information. We need to know specifically ALL of the differences between the two shots. Simply changing a lens does not account for the differences. Focus, DOF, and FOV are all important factors, and are all affected by camera position, focal length, focus setting of the lens (are they both focused at their closest focus setting?), etc. Can you explain in more detail exactly how you took each shot? – jrista♦ Oct 8 '11 at 18:07
@JukkaSuomela: you were right. When shooting something far from cam, the field of view is pretty the same. If you put it in an answer, I will mark it as accepted answer. – gsharp Oct 8 '11 at 20:28
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3 Answers

up vote 4 down vote accepted

When both set to 100mm, the field of view is the same - the difference comes where the macro lens can focus much closer; which gives much higher magnification ratios of the image on the sensor.

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Sorry lack of english. Are you saying that there is a difference because it's a macro, or that at 100mm the field of view should be the same? – gsharp Oct 7 '11 at 21:24
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Same focal-length on same body = Same field of view (or extremely similar as there is some small tolerance) – Itai Oct 8 '11 at 1:57
@Itai but why then it's not in my case? I've updated my quesiton with the two pics in question. – gsharp Oct 8 '11 at 6:40
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@gsharp Are those two samples taken with the camera on exactly the same position (i.e. on a tripod, or similar) – Rowland Shaw♦ Oct 8 '11 at 12:53
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@Itai read the comments of Jukka Suomela in my questions. That explains it pretty good. – gsharp Oct 9 '11 at 8:30
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up vote 1 down vote

Focal length figures are measured with the lens focussed at infinity (i.e. as far away from macro as you can get). Even then they are rounded up or down - it seems an error of up to 10% is acceptable, meaning your 100mm lens could be 90mm or 110mm.

At macro distances the focal length does change, sometimes quite considerably depending on the focusing method (rear internal focus mechanisms like the 100 macro change focal length more than front group extending focus mechanisms).

So I would expect the field of view to be different when both lenses are set to "100mm", but I'm still perplexed by how the zoom lens at 200mm appears to be wider than the 100 macro, this seems like far more variation in focal length than I would have thought possible.

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I'm wondering if he's tried focusing at the closest focus distance for each lens? In the EXIF info there's "Focal Length (in 35mm film)" of 313 vs 626 which is confusing me and making me think that he's zoomed in more with the 200, but moved back to focus at the closest point. Probably just odd exif data though as it's clearly just double the other – Dreamager Oct 8 '11 at 11:19
@Dreamager not closest, but pretty close. – gsharp Oct 8 '11 at 20:33
So you have moved the camera with each shot to get pretty close? Or it's stayed in the same spot? – Dreamager Oct 11 '11 at 8:23
up vote 0 down vote

Seeing the images the focal length is obviously different. My guess would be that the 18-200 lens is reporting focal length incorrectly on EXIF data.

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nope it's not. I put the zoom to the max on 200mm – gsharp Oct 8 '11 at 10:09

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