Sunday, January 20, 2008

Sigma 600mm f/8 Pre-Review

I have a ton of tests, images, and documentation I want to do for the Sigma review, but I wanted to get some early information posted about the Sigma 600mm f/8 mirror lens I won on eBay with an EOS/FD mount adapter because the full review will take me a while.

As usual, all photos in this post can be clicked to see them larger.

First, the obligatory moon picture, shown at the top of the post. The Sigma 600mm with the 20D crop factor produces a 35mm equivalent of approximately 960mm. In reality, it is probably a bit longer than that (maybe 1100mm?) because the adapter works as a small teleconverter. The result is a full frame image shown below -- approximately 20x magnification and the diameter of the moon is half of the vertical frame dimension.

To put it in layman's terms, the thing feels like a friggin' telescope. Any minor hand shake is magnified in a big way, and getting solid shots requires a super-fast shutter speed (1/1000s or faster) or a quality tripod. For this setup, my cheap tripod doesn't cut it very well.

On the flip side, the lens itself handles like a dream. The focus wheel is wonderfully damped and it feels very solid in my hands. Nothing about the lens is cheap, from the rear-filter holder to the barrel markings to the machined metal hood.

Sadly, on my initial inspection I found some small blotches of mold/fungus on the main mirror. I'll talk more about that in another post with some images of it. To be honest, I'm not planning on returning the lens but I may ask for a partial refund. I don't think the damage hurts image quality noticeably but it will definitely hurt resale value of the lens if/when I decide to get rid of it.

Quality-wise, the images are so-so. The raw, 100% crop from above (with exposure compensation as needed) is below. Pretty soft by my standards, but still substantially better than upsizing an image from the Canon 70-200mm F/4 USM.

The moon pictures were taken the first night after the adapter arrived (Saturday night). Today I wanted to get some pictures outside, but as luck would have it, it was one of the rare overcast California days. On an overcast day, you absolutely need a tripod with this lens. My only subjects were some ravens (I believe) but I was able to get a few good images of them. Both these images are essentially uncropped.

Pretty good for shooting to my roof from about 15 yards away. Again, the Sigma 600mm has some extreme reach. Also, note the donut-shaped bokeh in the background of the second image which is a hallmark of all catadioptric lenses. In this case, I actually don't mind it at all.

For the images above I tried removing the glass from the FD to EOS converter and it seemed to help the quality some (not as much as I hoped though). Surprisingly, the lens focuses far enough past infinity that the unglassed converter almost gives me infinity focus. An unedited 100% crop is below.

I will say, even though the 100% sharpness isn't great, I love the quality at 50%; the lens has very few aberrations and the softness is relatively easy to address in post-processing as long as you aren't printing a poster. Ultimately, I think getting a clean shot without vibration will outweigh the image limitations of the lens. Considering I got a passable 600mm lens for about $100, I'm pretty happy. Once I've had some more time with the lens in sunny conditions, I'll be able to say more.

In the meanwhile, let me give you a little teaser about posts I'm planning for the next few weeks:

  • Full Sigma 600mm F/8 review with comparisons to Canon 70-200mm F/4 USM.
  • Full FD/EOS converter review and discussion (I'm pretty happy with the $35 model I bought).
  • A brief guide to buying used lenses on eBay.
  • A guide to dealing with fungus on a lens.
  • A brief teleconverter guide.
  • A Canon FD 100mm F/4 Macro review (yeah, just bought one today!).

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