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06/24/2004 12:35:32 PM · #1
I'm thinking of getting the Canon 100 or the Sigma 105. Any opinions either way? Also, does 1:1 or lifesize mean the image on the sensor is the same size as the image being taken? If so, does that mean the 300D with a 1:1 lens actually gets you 1.6x lifesize?
06/24/2004 12:44:21 PM · #2
It meams that the image on a 35mm frame is lifesize, so what you will get with the Rebel is a crop from that image. It will appear to be 1.6x bigger than it would have been on film, but only because it's cropped.

So I guess the answer is yeah ... sorta.

As for the lenses - I believe both are very good, as is the Tamron 90. Sigma has a new version of the 105 on the way too.
06/24/2004 12:46:52 PM · #3
Both are probably about the best lenses that either company produce.

The Canon one usually gets better ratings for build/ focus speed/ handling compared to the sigma, but often focus speed isn't an issue and they both give stunning images.

magnification ratio and 'life size' is based on the sensor size. The 300D and other 1.6x 'focal length multiplier' cameras have a physically smaller size.

The image formed by the lens is still the same size - i.e., still life size. You then take a crop out of the middle of that image - so that is still life size - its just a smaller part of the scene. Least that's how my current thinking goes :) So no - a 100mm macro lens can form a life size image, big or small sensor. It does give the equivalent focal length of a 160mm lens when used in 'non macro' terms, but magnification-wise it is still 1:1

Message edited by author 2004-06-24 12:49:21.
06/24/2004 12:46:58 PM · #4
I have the Sigma and would recommend against picking it up, unless you like having to "pop your barrel" and flip a switch just to change AF to MF (and back). You can easily forget to switch one or the other (usually the barrel pop) leaving you with soft images. Otherwise, it's a great lens. Oh, I think the Canon is all internal focusing, which you might consider important for your application.

Re: magnification. No, it's 1:1 at the sensor plane. The smaller sensor just leads to a crop, so you'll see less of the same object at the same magnification.

Edit: I believe the new incarnation of the Sigma 105 will still suffer from the barrel-pop plus switch-flip AF/MF issue. Suckage.

Message edited by author 2004-06-24 12:49:11.
06/24/2004 12:49:09 PM · #5
Originally posted by dwoolridge:

Oh, I think the Canon is all internal focusing, which you might consider important for your application.


The canon is all internal, so the lens stays the same length and any filters don't rotate during focusing.
06/24/2004 12:51:22 PM · #6
Originally posted by Gordon:

The canon is all internal, so the lens stays the same length and any filters don't rotate during focusing.

Ahh, the Sigma is rotation-free (at the end, where the filter goes), but not length invariant.
06/24/2004 12:55:15 PM · #7
Yes, I also found this to be incredibly annoying. My personal favorite lens from the Sigma lineup is the 50mm f/2.8 macro EX. I have tried many of their lenses including the other two macro lenses and I fully believe that the 50 is the best lens they make. The Canon 100mm f/2.8 macro USM is an awesome lens also and would be my choice in the 100mm range because of its internal focusing, USM and slightly superior optics. The Tamron 90mm is pretty nice also. I am excited to see how the new Sigma macro lenses are because I must say that I have been totally thrilled with the 50 and if they can improve on that and bring the 105 to itís level I will certainly own both.

Greg

Originally posted by dwoolridge:

I have the Sigma and would recommend against picking it up, unless you like having to "pop your barrel" and flip a switch just to change AF to MF (and back). You can easily forget to switch one or the other (usually the barrel pop) leaving you with soft images. Otherwise, it's a great lens. Oh, I think the Canon is all internal focusing, which you might consider important for your application.

Re: magnification. No, it's 1:1 at the sensor plane. The smaller sensor just leads to a crop, so you'll see less of the same object at the same magnification.

Edit: I believe the new incarnation of the Sigma 105 will still suffer from the barrel-pop plus switch-flip AF/MF issue. Suckage.
06/24/2004 02:50:41 PM · #8
I personally want the sigma 180mm 3.5. But then again I am weird. A couple of things I like is that you don't have to get so close to the subject and the other is it has the hsm autofocus motor.
06/24/2004 08:10:33 PM · #9
Thanks everybody! Now I feel safe adding yet another lens to my wishlist.
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