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08-28-2009, 08:39 AM   #1
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Is a pentax or sigma for sharpness

I have had some great advice on this site regarding the sharpness of my photos taken with my 300ml zoom. Mainly that my lens is not the sharpest.
I found a Pentax 80-320 f4.5 5.6 lens here on Oz Ebay, and it looks OK but the seller is replacing it with a Sigma 70-200 f2.8. Any one know how it would compare with my Sigma 100-300ml 1:4.5-6.7?? Not sure I will be any better off.
Meanwhile thanks so much for all your advice here, I really do appreciate it, and will certainly try some of your advice. Seem to do ok with stationary objects, but must admit just not as sharp as I would like. I might even try my old manual 70-200 pentax lens. Thanks again.

08-28-2009, 08:46 AM   #2
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I disagree the problem is that your lens is not sharp enough. For a 100% crop, that's probably as sharp as *any* lens that would cost under $1000. I think the main problem is that your lens simply isn't long enough - if you had a 500mm lens or more, you wouldn't need to crop as much. I'd also susp[ect a faster shutter speed and/or a tripod would help, although perhaps you were already doing that. Anyhow, again, I mostly think you're placing unreasonable expectation on what can be done with a 300mm lens, especially one that costs under $1000. Had you beed close enough that you didn't need to crop to that level, I think the image would have been fine.
08-28-2009, 09:26 AM   #3
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The seller is probably replacing that lens for the Sigma because of the f2.8. I would like that lens also but it's out of my price range right now. I have heard that the 100-300 is a very sharp lens. It's also very expensive if it is the same one I am thinking about. I use a very inexpensive Sigma 70-300, not known for being the sharpest thing around either but using a tripod/monopod and staying around f/8-f/11 I have got some very sharp photos even extended to the 300mm end and cropped. The Pentax 80-320 is probably a better lens or certainly as good. With long zooms it all comes down to price but even the "cheap" ones have their sweet spot. If you want fast and sharp throughout the whole range of length and aperture then be willing to pay for it.
08-28-2009, 04:08 PM   #4
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Well IMO you won't be any better off. Both of the lenses you mention are consumer grade lenses. The Sigma 70-200/2.8 is an EX lens i.e. the top line of Sigma. I only own EX lenses and they are stellar lenses providing you get a good copy. As with any lens manufacturer, Sigma also seems to suffer from QC issues every now and again. I have been very lucky and all my copies are tack sharp.

When you mention sharpness; it depends what you use the lenses for and as others have said, if you have to crop a lot, image quality will suffer. Then again, EX lenses will provide better results when you crop. The downside is that they are very expensive and as with anything else; you get what you pay for.

If you find that you need to crop your image a lot, you are probably better served with a longer focal length. You don't state what you use the lens for.

08-28-2009, 04:18 PM   #5
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Trish, those consumer lenses can only perform so well, even under optimal conditions.
One lens you may consider within your budget and still give you reasonable results is Pentax's own DA 55-300. A little more expensive than the other 70-300s available (and much better than the FA 80-320) but considerably better sharpness (even at 300mm) and colour rendition.

I've just posted up a couple of photos from a garden I got using my own 55-300 on this thread:
https://www.pentaxforums.com/forums/post-your-photos/71469-more-bright-flowers.html

The first two were taken at 300mm, f/8 - this is where this lens performs its best, but you do need good sunlight for this lens to shine like it does here - not so good for indoors stuff, which is why I also have one of those 70-200 f/2.8 lenses...
08-28-2009, 10:06 PM   #6
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QuoteOriginally posted by trishytee Quote
I have had some great advice on this site regarding the sharpness of my photos taken with my 300ml zoom. Mainly that my lens is not the sharpest.
I found a Pentax 80-320 f4.5 5.6 lens here on Oz Ebay, and it looks OK but the seller is replacing it with a Sigma 70-200 f2.8. Any one know how it would compare with my Sigma 100-300ml 1:4.5-6.7?? Not sure I will be any better off.
Meanwhile thanks so much for all your advice here, I really do appreciate it, and will certainly try some of your advice. Seem to do ok with stationary objects, but must admit just not as sharp as I would like. I might even try my old manual 70-200 pentax lens. Thanks again.
Wouldn't piss on a Sigma if it were on fire.

Consumer-grade Sigmas are terrible lenses, and CRK's copped a lot of flak (rightly, in this poster's opinion) for only selling Pentax bodies with Sigma lenses (which does nothing for Pentax's image) in Aus at least up until recently.

My thoughts are that the Pentax would eat the Sigma for breakfast (the resulting digestion and excretion would no doubt improve the Sigma, though.) Consumer-grade Sigmas are famous for chromatic aberration, high distortion and softness, and I've found that to be the case.

I just picked up an SMC-F 100-300mm f4.5-5.6 for $90. Good contrast, fairly sharp, excellent build - there's metal on there, and it's an internal zoom - and it's faster at the top end than the Sigma. There's a bit of chromatic aberration (purple fringing) but it is a consumer lens.

I am certain the 80-320 will have better quality than any similar Sigma.
08-29-2009, 02:22 AM   #7
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QuoteOriginally posted by lithos Quote
Wouldn't piss on a Sigma if it were on fire.

Consumer-grade Sigmas are terrible lenses, and CRK's copped a lot of flak (rightly, in this poster's opinion) for only selling Pentax bodies with Sigma lenses (which does nothing for Pentax's image) in Aus at least up until recently.

My thoughts are that the Pentax would eat the Sigma for breakfast (the resulting digestion and excretion would no doubt improve the Sigma, though.) Consumer-grade Sigmas are famous for chromatic aberration, high distortion and softness, and I've found that to be the case.

I just picked up an SMC-F 100-300mm f4.5-5.6 for $90. Good contrast, fairly sharp, excellent build - there's metal on there, and it's an internal zoom - and it's faster at the top end than the Sigma. There's a bit of chromatic aberration (purple fringing) but it is a consumer lens.

I am certain the 80-320 will have better quality than any similar Sigma.
Couldn't agree more on the thoughts of a Sigma lens.Like lithos says about selling Pentax camera with Sigma lenses.To me it is a rip!!I got the 18-50 Sigma lens with my K100D and must say it would be better off as a door stopper,and the thing is,we are paying top dollar for these type of( Sigma) kit packages.Give us here in Australia FULL PENTAX GEAR FOR A DECENT PRICE!!!
08-29-2009, 04:18 AM   #8
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Thanks again. I think I shall go hide in the bushes and get closer to these blue birds. As for the birds of prey that I try to shoot I think I will have to save my pennies. Still not sure about the Pentax Lens I mentioned as some seeingly conflicting views here. But I have learned a lot anyway! (um not sure of some of the abreviations used here, what is an EX lens ) Marc I think you might be on the right track as I have a very sharp pic of what we call here a 'willy wagtail' even the drop of water on its beak is sharp. It just happened to land on a twig very close to me. It is cropped up a little as it was still a little too far to avoid using the 300ml range. Thanks


Last edited by trishytee; 08-29-2009 at 04:23 AM.
08-29-2009, 04:37 AM   #9
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Hi Trish,

I assume you are referring to my reply. The EX range of lenses are the pro grade lenses of Sigma. Similar to the DA* line of Pentax.

The longest lens I currently own is the Sigma 100-300mm F/4 EX DG APO IF which is a stellar lens. Then again, I've heard of someone having a lot of problems with it. Sigma did in the end replace the lens and his copy is tack sharp as well now.

Saying this, if you use your lens for birding, you'd probably be better off with something in the 400-500mm range. Since Pentax doesn't do anything longer than 300mm in the current range, you probably need to look at the current Sigma range or older Pentax glass but you'd be paying a premium for them (if you can find any).

This was taken with the Sigma and is quite a heavy crop. I know, it is not a bird but it gives you an idea of the quality.


Last edited by Cloggie_UK; 08-29-2009 at 04:46 AM.
08-29-2009, 04:37 AM   #10
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QuoteOriginally posted by trishytee Quote
It is cropped up a little as it was still a little too far to avoid using the 300ml range. Thanks
If you dial it back just a little bit from the 300mm extreme, you might be surprised at the difference. The extremities (both ends) are usually softest. Unfortunately at the long end, softness/blurring will be worse because the tiniest movement on your part is magnified.
08-29-2009, 04:38 AM   #11
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I would agree to look into the 55-300 Pentax DA lens. It has had generally good reviews. I had one Sigma lens (since gone) and unfortunately for whatever reason, even stopped down it was very soft. It also produced quite different colors from what I was used to from my other lenses. I know many like the Sigma EX lenses and I wouldn't disparage all their products, but certainly their cheap zooms seem to be lacking.
08-29-2009, 06:27 AM   #12
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I agree that 300mm is too short for birding--I have the DA*300mm but almost always use it with a tc for birds. As a rule, I think IQ will suffer if you're getting to 300mm at the long end of a zoom--especially if you're going to use a TC. That said, I'll agree that the DA 55-300mm is very good--in it's price class.

I'm also going to dissent from the vituperative posts regarding Sigma lenses: I have several (10-20mm, 24-60mm, 105mm, and 70-200mm) and couldn't be more pleased with them. All manufacturers, even (gasp) Pentax, have QA issues from time to time. Apparently, Sigma had some in the past but, of late, their record seems to have been very good indeed.
08-31-2009, 07:06 AM   #13
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QuoteOriginally posted by Barnster Quote
Couldn't agree more on the thoughts of a Sigma lens.Like lithos says about selling Pentax camera with Sigma lenses.To me it is a rip!!I got the 18-50 Sigma lens with my K100D and must say it would be better off as a door stopper,and the thing is,we are paying top dollar for these type of( Sigma) kit packages.Give us here in Australia FULL PENTAX GEAR FOR A DECENT PRICE!!!
So I assume, that you have used the Sigma EX 18-50/2.8 or the EX 10-20mm or the EX 50-500 (aka Bigma) etc. and you have made abyssmal experiences with those to support your very negative notion? This is the Sigma lens line, René referred too.

I have all of those and a couple more and have not had a single Sigma EX lens underperforming. My Pentax DA 16-50/2.8 is currently in repair, because the zoom ring jammed and the AF is performing erraticsely. My Sigma 18-50/2.8 is tack sharp and never caused any problems. THAT is my real life experience!

Nevertheless I wouldn't call ALL Pentax lenses crap, not even the DA 16-50, as it is a very good lens, when it works. Pentax has just got exactly the same quality check problems, ANY other manufacturer has got. (Though, again I have to state, none of my 5 Sigma EX lenses caused any trouble.)

Ben
08-31-2009, 09:26 AM   #14
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And to add to that; Sigma EX lenses here in the U.K. come with 3 year warranty. Also here in the U.K. (I can't speak for other countries) Sigma service is excellent with very fast turn around if you do have a problem (not my personal experience as I've had no issues but I've seen quite a few reports from people who have used their service). One person (in Canada) had loads of problems with his 100-300/4 EX. Sigma replaced his lens and due to the wait for a new batch to be delivered they gave him a Bigma on loan in the mean time so he wasn't without a lens. Pentax can learn something here.

Last edited by Cloggie_UK; 09-01-2009 at 04:02 AM.
08-31-2009, 07:57 PM   #15
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QuoteOriginally posted by Ben_Edict Quote
So I assume, that you have used the Sigma EX 18-50/2.8 or the EX 10-20mm or the EX 50-500 (aka Bigma) etc. and you have made abyssmal experiences with those to support your very negative notion? This is the Sigma lens line, René referred too.

I have all of those and a couple more and have not had a single Sigma EX lens underperforming. My Pentax DA 16-50/2.8 is currently in repair, because the zoom ring jammed and the AF is performing erraticsely. My Sigma 18-50/2.8 is tack sharp and never caused any problems. THAT is my real life experience!

Nevertheless I wouldn't call ALL Pentax lenses crap, not even the DA 16-50, as it is a very good lens, when it works. Pentax has just got exactly the same quality check problems, ANY other manufacturer has got. (Though, again I have to state, none of my 5 Sigma EX lenses caused any trouble.)

Ben
You may be right about how good some of the Sigma lenses are that you have mention,but as I was saying in my comment,that the Sigma kit lens(18-50mm) that we get over here is nothing more than a dust cover for the great Pentax camera.And when we want the better Pentax equivalent,we have to pay a whole lot more for that privalege.
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