Pentax 560mm lens now listed on Adorama...any takers!

Started Nov 5, 2012 | Discussions thread
falcon_wizard Regular Member • Posts: 316
Re: Overpriced product - just buy Sigma 500/4.5

Greyser wrote:

Interesting observation. Thank you.

I had a few encounters with the older Sigma long telephotos: two Sigma 100-300/4 and one 400/5.6 TeleMacro (unfortunately with crippled AF).

Perhaps due to my limited time with these lenses (I decided do not keep them) I came to interesting conclusion: these Sigmas did not withstand aggressive cropping as well as similar aged Pentax FA* or newer DA* lenses, especially when shot is taken with assistance of 1.4-1.7x TC.

Most likely it is only mine observation, though. Could you comment on this please?

Thank yoiu in advance,


Hi Greyser,

I have not handled the 100-300 or the older 400/5.6, so I do not have first hand comparison. I do recall however that the MTF on Sigma's site clearly showed that the 500/4.5 was significantly sharper than the 100-300 (not sure it is still available). The 500/4.5 seems to actually be the sharpest of all Sigma's super tele or tele-zoom (800/5.6, 300-800, 300/2.8), except for the 32k$ 200-500/2.8, which shows better MTF at 2.8 that the 500/4.5 at 4.5 (quite an achievement!). Most Sigmas are not exceptionally sharp compared to top of the line lenses of Nikon, Canon or Pentax. The 500/4.5 is probably the exception in that category of pro lenses. They do have however a lot of "very good" (but not stellar) consumer/enthusiasts lenses. Maybe the new lenses are better now that they make their own bodies, I'm not sure.

As I was indicating in my above post to Leopold, shooting with a TC constrains your "operational envelope' quite a bit if sharpness needs to be maintained. As such, magnifying a less than tack sharp shot will simply magnify the defects in the image. Working effectively with TCs require practice, good skill/set-up and an understanding of the limitations. What people may forget to do is to stop down at the lens's sharpest aperture when using a TC, such as to minimize the drop in IQ. Using a TC and then shooting wide open to account for the light loss usually means all those images will end up in the recycle bin, unless the lens you used is at its sharpest wide open. The Sony 70-400 is one those lens, which is sharpest wide open at 5.6. The Pentax 60-250 is also very sharp at f/4.

Now cropping in itself does not affect sharpness. If your image is tack sharp when looking at 100% view, then it is sharp. You can crop and keep the part you want. Provided you have sufficient pixels left for the final size of web/print you need. When I assess sharpness on my wildlife images, I always look at them at 100%. So yes I am setting high expectations on the results, but this is the bar I set for myself for what I want to do.

So, if you use a lens that is not all that sharp on its own to begin with, and add a TC on top of that, shoot wide open and hand held for example, you can quickly see how everything will just add-up to make a shot that will go to garbage! The sigma 500/4.5 definitely can provide usable (ie very sharp) results with both the 1.4 and 2x TC in the proper conditions (lots of light, light wind, etc) and with the right technique (stopped down to sharpest aperture, tripod, long lens technique to dampen vibrations, high enough shutter speed based on final effective focal length...).

Hope this helps..!

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Stephane Neron

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