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I am a Canon user, wanted a great all-purpose walk around lens, so bought the Sigma 18-200mm last year but was never happy with the results and found myself avoid using it and take my heavy Ls instead.
After reading a number of good reviews about the Nikon 18-200mm VR, decided to take the plunge and purchase the D200 and the 18-200 lens. Went to my favourite camera shop (they had a D200 and the lens available), but decided to test it against my Canon 30D+Sigma 18-200mm ….. and pleasantly surprised by the results. (VR on the Nikon was switched on during my test and the shooting mode was set to Av for both cameras)

http://www.stevesforums.com/forums/atta ... p?id=94609

What was strange, I found the Sigma to be much faster than Nikon …. Can anybody explain?

Can I clarify what you meant by much faster ?
Do you mean faster focusing ? (if so VR is said atleast by some to slow down the AF speed of the lens).

What I don't get is that you didn't use the same aperture/shutter speed for comparison. How else are you going to get a true picture of whether the VR is worth it etc?

The Sigma does look a little more contrasty and sharp, but I'd be interested in a comparison where all the settings were equal.

What I meant with faster is the shutter value was much higher on Sigma. Please note the photos are 100% corp

omik wrote:What I meant with faster is the shutter value was much higher on Sigma. Please note the photos are 100% corp

ahhh i see. Did you use the same camera? Or were you using the 30D with the Sigma? I would say that the two different cameras meter differently, so there's a chance you will get a difference.

are the images as shot or processed

ISO 200 on the Nikon may not be equivalent to ISO 200 on the Canon ?
(That's possible right, as far as I know) and as Des has said, they might be metering differently too.. where theses shots jpegs ?

Please forgive my English I will try to explain once more:

Both cameras were set (fixed) to:

- Aperture priority modes
- f/6.3
- AWB
- Center AF point
- ISO400 (I only mover the ISO up to 3200 on my last shoots for both cameras as I was shooting indoor).
- JPEG mode
- shots were not processed, just cropped in the center so 2 shots can be viewed side by side

Even so the aperture was the same, Sigma gave me a much higher shutter speed …. Maybe it has something to do with the lens size? As the Sigma is shorter than Nikon

I reckon it has more to do with difference in bodies than anything else. Unless you test both lenses on the same body, it's not a fair comparison.

To my mind this indicates a differential between metering systems on the two cameras.

and the winner is........

no-one here. Not a great test really. Are you testing the 30D v's the D200, or your handholding technique ? Your topic name suggests a lense comparison test but your questions further on indicate an interest in shutter speeds and apertures...

A better test here would be to get a Nikon mount Sigma lense and test them side by side on the D200.

Justin

Weird. I have the Sigma and I HATE IT!! I am so sick of the huge lack of sharpness from it. I wanted to get the 18-200VR but this has changed my mind.
I am probably going to just save up and get a 24-85 f/2.8-4, sigma 10-20 and the awesome 70-200 f/2.8 VR

As others have noted, you may well be seeing differences in the metering rather than the lenses.

It might be good to do a test with both cameras and various lenses on each camera using the "sunny f/16 rule"*. In bright sunlight, the correct exposure should be f/16 with the shutter speed as close as possible to 1 over the ISO. For example, if the camera is set to ISO 200, the shutter speed would be 1/200.

For each camera and each lens, set the camera at ISO 200 in aperture priority and the lens at f/16 and focus at infinity. Go outside on a sunny day and point the camera to a clear patch of sky to the south about 45º above the horizon. The camera should choose around 1/200 s. See what each camera does and whether different lenses change the reading. That way you will at least know where the metering differences are.

* From John Shaw's The Nature Photographer's Complete Guide to Professional Field Techniques.

losfp wrote:What I don't get is that you didn't use the same aperture/shutter speed for comparison.

Canon consistently come out ~1/3 stop faster for "the same" ISO in photo reviews. So that explains some of the difference.

Buyers remorse probably also plays a part.