Mirror telephoto lenses

<p>I don't take a lot of shots where I'm seeking a lot of reach...I have a 70-200 f/2.8 L with a 2x TC, so when considering long lens options, I'm comparing against that...400mm f/5.6 IS. So while I know that the 400mm f/5.6 prime would give me better IQ, I can't justify the expense on that slim of a margin for a lens I won't use often. Anything 200mm+ and faster is out of my price range for much the same reasons. So, I picked up used a Sigma 600mm f/8 from KEH. It's slow, and manual focus, but for the price, I can't beat it, considering that overall, the use will be infrequent at best.</p>

<p>That said, the biggest issue I've seen with these kinds of lenses is the doughnut-shaped bokeh that can be very distracting. While I don't expect this lens to be as sharp as an L prime, would I be better off stacking TCs as far as IQ is concerned? It's manual focus either way, so IQ is really the only issue...I could tack on another 2x TC and have an 800mm f/11, or a 1.4x TC and have a 560mm f/8, not much different than the mirror.</p>

<p>Thoughts? As I said, anything longer/faster than the 400mm f/5.6 isn't really an option considering frequency of use: cost ratio, and that's out seeing as I can match it with my current equipment.</p>

<p>My guess is the mirror will be better than stacked TCs. I've never used the Sigma 600 but I have briefly reviewed the Tamron 500/8 and found it to be pretty sharp. See <a href="http://www.bobatkins.com/photography/tutorials/mirror.html">http://www.bobatkins.com/photography/tutorials/mirror.html</a> for some comparison shots against a Canon 500/4.5L</p>

<p>I'd agree that the Canon 400/5.6L is your best bet if you want optical quality, good bokeh and convenience (AF, variable aperture etc.). It also takes the Canon TCs.</p>

<p>Thanks, Bob. I read your article, I think it will be passable. I might do some tests and compare the double stacked TCs vs the mirror and see how that works out.</p>

<p>There's a Sigma 500/7.2 (ordinary telephoto, not mirror) which you may be able to find cheaply. It is not electronically compatible with newer Canon bodies but it may work wide open. At a maximum aperture of f/7.2, wide open is probably fine.</p>

<p>I doubt that stacking two teleconverters will give you any improvement in quality over just cropping out the centre part of the image and scaling it up in software.</p>

<p>I owned the Sigma 600mm mirror many years ago, used with Olympus OM. I recall the pictures being on the low contrast side. I replaced it with the Olympus 500 mirror lens, and those pictures were noticeably snappier. Maybe some of the low contrast can be overcome in post processing.</p>

<p>Looks like mirror lenses are making a bit of a comeback. Tokina just announced a tiny 300mm one for m4/3 cameras.</p>

<p>Mirror lenses are not perfect. They have their hotspots because of their construction. They are devilishly difficult to focus because of the very shallow depth of field, and they do have 'donuts'. Contrast is said to be low, although I suspect most cases cited are the result of flare. They definitely need a deep lens hood.</p>

<p>All the same, they are a very cost-effective solution to the problem of needing a long lens occasionally. I got into a kind of obsession with them a few years back and so tried out many of them (sad, or not, story at http://www.photo.net/classic-cameras-forum/00RaKy ). I also, the last one so far, got a Sigma 600 f/8 (report at http://www.photo.net/classic-cameras-forum/00XSrL ). It and the Nikkor 500mm f/8 were the pick of the lot, although the later Spiratone mirror lenses were also decent). The Sigma came with a deep hood which also helps a lot.</p>

<p>As it happens just last week I did a tour of the Missouri Botanical garden and one of the kits I carried was this Sigma 600mm (and a monopod) on a Canon 20D. Worked fine and gave me a new perspective on a commonly shot subject of mine. I also used it later on my 5D where it produced satisfactory results, as well.</p>

<p>BTW, you can also use older teleconverters for the original mount on the lens to boost these suckers up considerably. Had to go out and buy a massive tripod to hold the nearly 2000mm equivalent. :|</p>

<p>Please look at my reply in <a href="00ROFu">this thread</a>.</p>

<p>Happy shooting,<br>

Yakim.</p>

<p>I think it performs fine. It's tough to focus accurately on even slow-moving subjects, especially when tripod mounted. The attached shot is with a 1.4x telextender also attached.</p><div></div>