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07-25-2016, 10:59 AM   #1
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Sigma 18-300 vs Pentax 55-300

Hi, I'm wondering how the Sigma 18-300 Contemporary performs in terms of sharpness specially at the long end 300mm versus the Pentax DA 55-300. Does anyone have both to compare?

Thanks

07-25-2016, 11:25 AM   #2
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dxo mark tested both om them:
Pentax smc PENTAX DA 55-300mm F4-5.8 ED on Pentax K-5 IIs vs Sigma 18-300mm F3.5-6.3 DC MACRO HSM C Pentax on Pentax K-5 IIs

Go to Measurements>Sharpness you can compare different focal lengths and apertures in different graphs. The Pentax is sharper at 300mm according to these graphs.
07-25-2016, 11:28 AM   #3
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I have both. In the centre, the Sigma is great, but border performance at any focal length and aperture isn't very good. If your subjects will be centred in the frame, the Sigma is very decent and has added flexibility in wide-end focal length range, though it also lets in a bit less light which can be important in keeping ISO down. But the Pentax has better frame-wide performance, and has nicer, more predictable bokeh. Which is the better choice depends on what you want to use it for...
07-25-2016, 11:30 AM   #4
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I have both and uses only 18-300. Seems center sharpness is better at 18-300 at 300mm than my DA 55-300 and my son's DA 55-300. I think 18-300mm is very good to be a superzoom.

Boer1974's Album: Sigma 18-300mm - PentaxForums.com

07-25-2016, 12:04 PM - 1 Like   #5
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I have both lenses and I have to agree with Mike; it depends more on how you intend to use the lens rather than overall performance. I also agree with Boer1974 that, at least for a superzoom, the 18-300 is a great performer.

When I can have both a wide-angle and the 55-300 along (and I don't mind changing lenses) it's better to have the 55-300 since it really does have better edge performance. But, more often I find that the convenience of having the 18-300 outweighs the modest performance gains with some subjects. For images of things that I intend to really only show central sharpness (eg, birds, portraits, flowers, etc.) the Sigma 18-300 is pretty good performer. But, long-range landscapes are much, much better via the DA 55-300 (for me, it's more because of the reduced vignette rather than the uniform sharpness).

I should add that prior to buying the 18-300, I was doing a lot of "one lens travel" with an 18-200. In that sense, the 18-300 now wins as the best way to find a middle ground (i.e. not having the reach of a 300 mm at all).
07-25-2016, 01:21 PM   #6
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The 18-300 is going to provide you with opportunities you may not want to miss with the 18 wide end. I had it, and a 55-300. The 18-300 has silent AF, the (not newest) 55-300 I had did not. Silent AF is available in the newest 55-300 though. The 18-300 and 55-300 both shoot nice images. The 18-300 has external barrel movement sometimes when AF is used, which is something I did not prefer, so I sent it back for a refund, though as I said it takes very nice images. I ended up getting a 16-85 (for portrait and landscape) to complement my Sigma 150-500 (for wildlife, out of reach flowers, birds in flight). If you do not mind the external barrel movement of the AF on the 18-300, I suppose it would give you more opportunity with the availability of the wide end without differing that much from the 55-300 on the longer end. If you do decide on a 55-300, I would recommend the most recent one available from Pentax, which has silent AF. I do not know if it is shipping yet, but most likely it will not be too much longer. Below is a shortcut to a plant I took a picture of with the 18-300 when I had it.

https://www.pentaxforums.com/forums/attachments/16-pentax-news-rumors/280007d...nt_example.jpg

Last edited by C_Jones; 07-25-2016 at 01:27 PM.
07-25-2016, 02:30 PM   #7
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The new 55-300 is KAF 4. it will only work with the K-70 and the K-1, K-3 II, K-S2, K-S1 after a firmware update.

07-25-2016, 04:17 PM   #8
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Also note the transmission curves at DXO. The Pentax is almost a full stop faster in the range 70-200mm.
07-25-2016, 04:28 PM   #9
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Very helpful and informed comments above. I haven't used the 18-300, but the reviews look promising. Even Lenstip, which is often scathing about superzooms, rates this lens quite well (tested on a Nikon): Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM review - Introduction - LensTip.com The results in that review are consistent with the user experiences described above.

I'd make two comments (drawing on my own experience with the Tamron 18-250, which was quite a good superzoom):
1. Typically for a superzoom, the 18-300 is about a stop slower than the 55-300 across most of their common range. The Pentax is f4 up to 125mm and then f4.5 up to 200mm, whereas (according to Lenstip's numbers) the Sigma is already at f5.3 by 85mm, f5.6 by 100mm, f6.0 by 150mm and f6.3 by 200mm. At 300mm the difference is f5.8 v f6.3, which doesn't sound like much but makes a real difference in practice. And when you consider that you need to stop down by one or two stops for best resolution, the Sigma does need good light.
2. According to another review, the Sigma exhibits focus breathing. That is, the effective magnification at any particular focal length varies according to the distance of the point focused on. That is common with internal focus lenses. You will see a number of discussions about it here. What it means in practice is that the field of view is wider than you would expect for a given telephoto focal length, unless the lens is focused to infinity (and maybe not even then). The Pentax is not an internal focus lens, and doesn't exhibit focus breathing. In simple terms, the field of view with the Pentax at say 300mm will be the same, whether the lens is focused at the minimum focus distance or infinity. So if you photograph a bird say 5-10m away at 300mm with the Pentax, it will fill significantly more of the frame than if you took the same shot with the Sigma. (On the Tamron, the difference was huge.)

So, for birds and other wildlife, and in mediocre light, the Pentax should perform considerably better. I should add that one upside of internal focus is that the Sigma has a much shorter minimum focus distance; the Pentax is a (sometimes frustrating) 1.4m.
07-25-2016, 06:59 PM   #10
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Thanks to all who replied. I actually have the DA 55-300 and I'm contemplating of upgrading to one that is sharper at 300mm(or longer) at wide aperture. I shoot mostly airshows and motorsports so subject isolation is rather important. I find my copy soft at f/5.8 and have to step down to f/8 or even f/11 to get the sharpness that i wanted and had to settle at higher ISO in the process. I'm hoping to find an affordable alternative and i think the Sigma 18-300 might be a good option. Another peeve i find in the 55-300 is its focus tracking capability. I use a K-3 btw. When a subject is locked and and fast approaching the lens will sometimes go berserk trying to re-focus by focusing all the way to infinity and back thus losing the opportunity. Not sure if the Sigma has this same issue.
07-25-2016, 07:02 PM   #11
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Hi,

Just thought I put tuppence worth in.

I've had a Sigma 18-250 and thought it was a great walk around lens but in a fit of madness I also bought a Pentax 55-300 thinking it would give me better IQ and a little bit longer reach, I was no too impressed. The 18-250 was in use everyday but when I came to use the 55-300 for some long distance work I was very disappointed with it, the Sigma was better at 250mm than the 55-300 and out at 300mm the Pentax was decidedly soft. I traded the 55-300 in for a second hand Pentax DA *300 and have never regretted it. I gave the Sigma to one of my daughters as I now use a FA 28-105 as my standard lens, this lens is awesome!

Nick
07-25-2016, 07:14 PM   #12
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QuoteOriginally posted by mazinger Quote
Thanks to all who replied. I actually have the DA 55-300 and I'm contemplating of upgrading to one that is sharper at 300mm(or longer) at wide aperture. I shoot mostly airshows and motorsports so subject isolation is rather important. I find my copy soft at f/5.8 and have to step down to f/8 or even f/11 to get the sharpness that i wanted and had to settle at higher ISO in the process. I'm hoping to find an affordable alternative and i think the Sigma 18-300 might be a good option. Another peeve i find in the 55-300 is its focus tracking capability. I use a K-3 btw. When a subject is locked and and fast approaching the lens will sometimes go berserk trying to re-focus by focusing all the way to infinity and back thus losing the opportunity. Not sure if the Sigma has this same issue.
What we all want: long, fast, sharp, quick-focusing and affordable. You need to compromise on some of those criteria.
07-25-2016, 07:35 PM   #13
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QuoteOriginally posted by Des Quote
What we all want: long, fast, sharp, quick-focusing and affordable. You need to compromise on some of those criteria.
I agree with you. I'm just looking for one step up or two without breaking the bank.
07-25-2016, 07:57 PM   #14
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I wonder if your 55-300 needed some AF adjustment; I've never had a disappointing copy and I've owned several On the other hand, an exceptional 18-250 is worth keeping, I've tried a copy or two of the Tamron model too!
07-25-2016, 09:35 PM   #15
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Sure a lens can make a difference in focus speed and accuracy. A lens with a long focus throw (e.g. the DFA 100) will take longer to acquire focus, a lens without a focus limiter can hunt over a wider range, and a lens which transmits less light (e.g. because its aperture isn't wide enough) makes it harder to acquire focus, and some AF systems in lenses work faster than others. But that's only part of the story. When I have trouble getting focus on moving subjects with the 55-300 and other screw-driven lenses, I attribute most of the problem to my technique (and maybe the settings in the camera) rather than to the lens.

Lots of users here get good shots of moving subjects with screw-driven lenses, including the 55-300. Screw-drive AF isn't necessarily worse than SDM/HSM. In fact the 55-300 out-performed the DA*60-250 in most AF tests: HD Pentax-DA 55-300mm F4-5.8 ED WR Review - Autofocus vs DA* 60-250 | PentaxForums.com Reviews

I'd start by working on trying to get better results with the 55-300 rather than just shelling out for another lens. Particularly one that is f6.3 at the long end. That's a recipe for disappointment.

If you do want a long lens with a wider aperture and faster AF performance, you would need to look at something like the DA*300 f4 or DFA 150-450. People do say that the DA*300 focuses accurately.

Last edited by Des; 07-26-2016 at 12:19 AM.
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