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08-05-2019, 02:55 PM   #1
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Sigma 170-500 APO f/5-6.3 DG or non-DG comparison

In reviews, the non-DG version (Sigma 170-500mm F5-6.3 APO Lens Reviews - Sigma Lenses - Pentax Lens Review Database) is described as the "full frame predecessor" of the DG version (Sigma 170-500mm F5-6.3 APO DG Lens Reviews - Sigma Lenses - Pentax Lens Review Database). I have an opportunity to pick the older (non-DG) version for a reasonable price and would be interested in hearing any insights into how much similar or different these two lenses are optically.
(I have read a lot of reviews and do understand the differences between these lenses and e.g. the 150-500).
Is there some major reason why non-DG is getting significantly lower ratings than the DG version, other than small number of reviews which makes both "scores" less reliable?
Interestingly, the reviews tend to mention the 500mm end of the (either) zoom being "soft", but the only test series of images at different focal lengths I could find, shows perfectly sharp images up to 500mm.

So my question really is: is the non-DG version, optically, just a version with slightly older coatings? Or has there been some optical change for the DG version?

08-05-2019, 04:58 PM   #2
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QuoteOriginally posted by Landscape_with_K1 Quote
the only test series of images at different focal lengths I could find, shows perfectly sharp images up to 500mm.
Perhaps that was my set in the samples thread: Sigma 170-500mm F5-6.3 APO - PentaxForums.com The distance to subject in that sequence wasn't far - less than 5 metres from memory. As other reviewers have said, the sharpness at the long end is OK when the subject is close, but the limitations were exposed at greater distances (many images were throwaways). The same is true of other consumer tele zooms, but it was quite marked with this lens.

To be fair, I should say that I was using it with the K-30 - I didn't have the K-3 then. But I found the Sigma 400 f5.6 tele macro on the K-30 a big improvement from the 170-500. The FA*300 f4.5 with 1.5x TC is better again. Either of those is a FF option too and the weight is comparable to the 170-500.

Given that the 170-500 was a FF lens, I was surprised by the vignetting I saw on a crop camera. That would be more pronounced on K-1.

I can't compare with the DG version, but you will notice that one reviewer ( @Alan C; ) has had both and found the DG to be sharper at longer focal lengths. Each has 13 elements in 11 groups and 9 aperture blades. Presumably the difference is in the coatings.

Personally I'd be a little skeptical about the high ratings for the DG version. I'd like to see a comparison with a Bigma (let alone a DFA 150-450) in controlled conditions on a high-resolution sensor before being satisfied that it really is worth a 9.

Last edited by Des; 08-25-2019 at 02:03 PM.
08-05-2019, 11:51 PM   #3
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Thanks and yes, it was your images I was referring to. That was a very good thread with (at least) two posters having very crisp images, and made me to jump into this opportunity in the first place. The reviews for the non-DG lens being a bit on the negative side, I would almost guess some of the reviewers never used a 500mm lens before (and neither did I, for that matter). I just remember having quite a learning curve with my 300mm lens as well: the first few times I though the lens is crap and it actually sat unused for a year or two first, but then I picked it up again, used a sturdy tripod, started getting good results. (Currently use it handheld too, now that I am familiar with how it behaves and how much light I need). I am still a bit hesitating about these (even) bigger 500mm lenses, realizing that will be the end of handheld shooting (and I usually carry my gear well "into" the landscape before shooting). But I think I will give this lens a try, largely thanks to the thread where your images were sharp up to 300mm.
08-06-2019, 12:58 AM   #4
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Well good luck with it. Having realistic expectations, committing to using a tripod and not laying out too much money are a good start.

08-06-2019, 03:22 AM   #5
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I can't speak of the differences between the two versions, but I have the DG version and I find it a good enough lens within its limitations. Mostly, this boils down to "stop down at 500mm (f/9 will do)" and "forget about birds in flight".

The vignetting is extreme on my K-1; I still have to try it without the hood to see if it makes any difference.

Basically, my advice would be if it's cheap enough, give it a try, as long as you have realistic expectations (and it looks like you do).
08-06-2019, 04:22 AM   #6
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QuoteOriginally posted by nono Quote
The vignetting is extreme on my K-1; I still have to try it without the hood to see if it makes any difference.
Interesting, and a bit worrying as well. Yours will vignet even when stopped down?

My purpose is to use this as a landscape lens (in wide open landscapes with fells or mountains) and I am not so much worried about the lack of brightness (as I have no need to catch any wildlife let alone birds in flight, and I will have a tripod). I have some ideas regarding shooting certain backlight scenes which brings into discussion the CA, which I have learned is going to be bad as well. But time will tell.

I could not immediately find a hood on eBay. Any tips welcome about where to find one. (A temporary hood you can easily make out of a sheet of paper but that is not very practical out in the wild..).
08-06-2019, 06:03 AM   #7
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I will try to post a few pictures showing the vignetting when I get back home this evening.
08-07-2019, 01:22 AM   #8
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QuoteOriginally posted by nono Quote
I will try to post a few pictures showing the vignetting when I get back home this evening.
I would be very thankful for that. Mine has not arrived yet, so I am still in the research phase..

08-07-2019, 05:27 AM   #9
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Oops, sorry, totally forgot yesterday. I will try to post these tonight.
08-07-2019, 01:41 PM   #10
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Here are a few examples, all at 500mm between f/9 and f/11. Just imported and converted in Darktable, no processing except the base curve. The images themselves are blurry and/or unfocused, but you can see the vignetting.







08-07-2019, 02:54 PM   #11
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Thanks a lot! Very good reference images. I do agree there is some vignetting. This type of vignetting is bad when you have clear sky or snow in the frame, and I am seeing that in some good-quality wide angle zooms as well, so it is nothing new. (Of all my lenses, some longer primes such as the Sigma 105mm and Pentax 85mm soft, are the only lenses where I do not see this). Sometimes, it can be difficult to correct in post processing. Having said all that, I am still quite confident that for most of my use cases, this vignetting is not going to be a problem.
08-19-2019, 08:52 AM   #12
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I now have the lens at hand and unfortunately, I think I will need a second opinion (other than mine) regarding its condition.

The seller's information about the lens was as follows: "In pretty good overall cosmetic condition with some light signs of age, wear and use. Clean internally bar the odd dust speck or two that are usually seen in used lenses."

Now, when receiving it, my immediate observation was that the second lens from the outer end, has got a "thick" coating of dust. Images included. I would hate to be the one who complains about a second hand item. I also sell my gear online myself, and it should go (almost) without saying that a used lens can have some dust. However, I have yet to see anything comparable to this one. With this information, would you others (try to) return it?





For some reason I cannot make the picture appear here, so I am adding links instead:
https://www.dropbox.com/s/xylicgr2ixyhcsn/2019-08-19%2018.33.33%20HDR.jpg?dl=0
and https://www.dropbox.com/s/h4wf0h6pw88q6ad/2019-08-19%2018.28.12.jpg?dl=0

Last edited by Landscape_with_K1; 08-19-2019 at 09:04 AM.
08-19-2019, 09:57 AM   #13
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It is an old lens. It is a zoom. So it will such in dust everytime you zoom in and out. I don't think this is exceptional in the sense that there is more dust then to expect for a lens this age that has been used. If that is acceptable. ......well depends on the price paid.

I owned the DG version for a short period in 2010. So I used it only on the K-7. The difference was the coatings if I remember right. It needs to stop-down for sharpness, so it does need a lot of light to work with. Going to f8 at least is recommended and even some more for 500mm.

This video was shot with the lens and zoomed in to 500mm.
08-25-2019, 05:01 AM   #14
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I finally had time to try the lens, even if only for a limited number of shots. It also was quite dull two days when I had it on camera, which tends to flatten the images. There was no wind, however, which made it possible to test it on a tripod and actually trust the results. I think the image quality is pretty okay for being the low-end 500mm option. Maybe a bit soft, yes, but not overly so. I also cannot see it being any worse when distance increases - would attribute this to athmosperic issues. Obviously you cannot crop the images like you can with the wide angle DFA lenses but this was to be expected. Unfortunately, I did not have a proper backlight situation to see if the excessive dust would have a huge impact, but did have some frames where I think I am seeing it. I would still be thankful for your comments regarding the dust situation. Are the images I am showinbg, reallty representative of typical condition for an older zoom lens (and then there is the question of not mentioning that in the listing).
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