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09-16-2015, 05:54 PM   #1
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Which Lens to Keep?

Okay, as the title suggests, I've got more lenses than I really need right now and two of them are very similar to each other, so perhaps it's time to re-home one of them by listing it on eBay. But which one to list and which to keep? The lenses in question are a Sigma 28-80mm f3.5-5.6 Aspherical Macro Zoom and a Quantaray 28-90mm f3.6-5.6 Aspherical Zoom. Comparing the two lenses side by side, they look almost identical, as well they should since the Quantaray lens was manufactured by Sigma for Ritz Camera.

The Quantaray, which I've had for about three years, has the advantage of a slightly longer reach (90mm vs. 80) but on the downside, it has a plastic mount. Pentax Forums rates this a lens a respectable 8.67. Somewhere, I have the original box for this lens, so it might be a little more attractive on eBay.

A recent acquisition, the Sigma has a shorter reach (80mm vs. 90) and although it has the same plastic construction as the Quantaray, it does have a metal mount. It's also got that nifty little 'Macro/Normal' switch on the side, not that it really does anything except lock the zoom ring in at 80mm--or does it? Pentax Forums rates this lens more than half a point lower at 7.93.

Whichever lens I keep will have a semi-permanent home on the front of my K100D as its default "walkin' around" lens. I'll probably be doing a shoot-out with the two lenses this weekend to determine a winner, but if anyone wants to venture an opinion, feel free.


Last edited by E-man; 09-16-2015 at 05:58 PM. Reason: more information
09-16-2015, 06:00 PM   #2
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I like the idea of the metal mount Sigma, but can't really give you a great reason. I just like the more durable mount.
09-16-2015, 06:20 PM - 1 Like   #3
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I don't have the mentioned Quantaray, but I DO have the Sigma 28-80mm and it is, without a doubt, one of my favorite lenses. I especially like the 1:2 macro feature. Despite it's rather less than stellar rating, my particular copy has always provided me with amazingly sharp images regardless of which FL I choose. It has also produced some amazing macro shots as well. It will be one of the last lenses I would ever part with.

Last edited by Dewman; 01-02-2016 at 07:10 AM.
09-16-2015, 06:23 PM   #4
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I'm with you there. The Quantaray is the only lens I have with a plastic mount and I've always felt like it's inherently more fragile than the metal mounts on my other lenses. One amusing factoid I forgot to mention in my initial post is the lenses are so similar that my cameras mis-identify the Quataray as a 28-80mm Sigma in the EXIF data.

09-16-2015, 06:24 PM   #5
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The mount being plastic or metal is irrelevant. I think I've heard of maybe 3 or 4 plastic mounts breaking and those were under circumstances that would likely have broken a metal mount too. Also, plastic mounts do not scratch up the camera mount like a metal mount lens will.

Is the Quantaray really 90mm on the long end? I mean have you tested them side by side for results? Sometimes the focal length is a bit odd (85mm for example) and one brand gets marked a conservative 80mm and the other an optimistic 90mm.

I would test them side by on the K10D against a few focusing targets and keep the one that gives you the better image. If you cannot tell the difference then sell the one that will bring the most money.
09-16-2015, 06:32 PM   #6
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I haven't done any side-by-side comparisons yet. I plan to do that this weekend. The Quantaray is physically a tad longer than the Sigma when zoomed all the way out, by maybe 1/8-inch but that doesn't necessarily mean anything.
09-16-2015, 08:01 PM   #7
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If the lens is almost always going to be on the mount - keeping the plastic one is going to matter little. i would shoot several subjects with both in varied conditions and compare the shots. It there is little difference pick one based on the mount or similar reason. If there is a optical difference there is your answer.
09-16-2015, 08:20 PM   #8
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That's precisely what I plan to do this weekend. I'm not expecting much, if any, appreciable difference between the two as they seem to be variations on the same design. I'm still curious as to whether that little "normal/macro" switch on the Sigma actually does anything beyond locking down the zoom ring at 80mm. The Quantaray lacks this switch.

QuoteOriginally posted by UncleVanya Quote
If the lens is almost always going to be on the mount - keeping the plastic one is going to matter little. i would shoot several subjects with both in varied conditions and compare the shots. It there is little difference pick one based on the mount or similar reason. If there is a optical difference there is your answer.


09-16-2015, 08:35 PM   #9
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On some lenses after it locks in a particular focal length that switch allows the focus ring to turn more I think.
09-16-2015, 08:54 PM   #10
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I had never noticed it before but the focus ring's turning radius more or less doubles in macro mode. Interesting.

QuoteOriginally posted by UncleVanya Quote
On some lenses after it locks in a particular focal length that switch allows the focus ring to turn more I think.
09-16-2015, 08:54 PM   #11
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The Quantaray has 9 blades vs the Sigma's 8. Not sure if it makes a difference or not.
09-17-2015, 02:36 AM   #12
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You may want to check the completed auction prices on eBay to see if selling is worth it or not. That zoom range is pretty common on the market.
09-17-2015, 02:16 PM   #13
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You're right. We're not talking high dollar stuff here. I might have a total of about $50 tied up in the two lenses.

QuoteOriginally posted by ramseybuckeye Quote
You may want to check the completed auction prices on eBay to see if selling is worth it or not. That zoom range is pretty common on the market.
09-17-2015, 06:52 PM   #14
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So when I got home from work this afternoon, I did a little "shoot-out" between the two lenses and came away with a few insights:

•Many of the images were indistinguishable from one another in terms of overall sharpness but Sigma lens did do a bit better with close-up work in macro mode.
•The Quantaray lens does indeed have greater telephoto reach as advertised.
•On a couple of shots, the Quantaray produced slightly brighter images; that is, objects in shadow showed up more clearly.

I'm still not completely sure what I want to do with these two lenses. The nice thing is I'm under no obligation or timetable to do anything. I'll probably continue to ponder this for a while and maybe even take a few more test shots to get a better comparison.
09-17-2015, 10:18 PM   #15
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What the mount is made of means absolutely nothing, it just makes the product "feel" more premium.

That being said, unless you need the extra 10mm, the Sigma being better at close focus stuff seems to make it a clear winner.

I would however do some controlled tests on a tripod and do some pixel peeping.
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