tamron 28-75 or sigma 24-60??

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which lens is sharp wide open? and which has better bokeh and less cromatic abberation? and which has quality control issue?
Sorry for my bad english

Haven't tried the Sigma, but here are some shots with the Tammy 28-75 wide open, on K100D + K20D:

K100DS:



Rest, K20D:

nero501 said:

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which lens is sharp wide open? and which has better bokeh and less
cromatic abberation? and which has quality control issue?
Sorry for my bad english

Click to expand...

I don't have them both and so cannot give comparison based on my own experience. I have Sigma 24-60 and absolutely love it.

The main reason I chose Sigma 24-60 was because of it's bokeh. The lens gives very nice rendering picking the main object (the focused level) from the rest of the picture (making them "smooth"). It is not on the same level as, say Pentax FA77 with it's wonderful 3D rendering, but it still really stands out of the competition. You can see it when you compare pics and valuate how much your eyes wander around the picture, are there something irritating in the background etc. Sigma 24-60 has 9 aperture blades which helps in making smoother out of focus highlights. This lens has been respected as wedding photography lens, according what I have read, because of it's characteristics.

Some pics taken by me that are still available on this forum:

http://forums.dpreview.com/forums/read.asp?forum=1036&message=29315182

http://forums.dpreview.com/forums/read.asp?forum=1036&message=27649564

Here is one Canon forum that has pics taken with the Sigma (hope this link works here, there are lots of pics on different pages of that thread):
http://photography-on-the.net/forum/showthread.php?t=392699

I have to say that, what has just been said about Sigma EX 24-60, can be quite likely applied to Tamron 28-75 also. The best images I have seen taken with it, show same kind of nice bokeh.

I think that there are lots of people happy with the sharpness of Sigma, although the "ravings" of the sharpness of the Tamron gives me the idea that it just might have edge here. I guess, the difference is actually more on the contrast level. I think Tamron is at least a bit more contrasty than Sigma and so gives appearance of sharpness more easily than Sigma. But, the less contrast that the Sigma has, makes it more suitably for example for portraits. My experience of the sharpness of the Sigma is that it doesn't lack sharpness compared to primes (at least on cropped sensor we now have on all Pentax DSLRs), although it is less contrasty than the primes.

If not counting the aperture blades (Tamron 8 versus Sigma 9) I would say the choice comes more to the question, which focal lenght is more suitable for you. Tamron lacks wide angle end and Sigma just and just might be wide enough for a walkaround zoom.

Sigma has had it's bad reputation what comes to "quality control". I would say it is actually more a question of correct focusing than "quality control". Some Sigma's need adjustment before it gives the best focus with a certain camera. But no manufacturer of lenses are without such problems. From other aspects I do not find anything that hints that this particular Sigma would be somehow of low quality, quite the reverse: I feel very condifent using it. I haven't encountered with chromatic aberration using this Sigma, my luck or indication of something, I cannot say. At least I have no bad words about the Sigma. Same goes probably with the owners of the Tamron.

Tough choice. Try them both, if possible, before the purchase. And there were some thread ages ago on this forum showing very nice pics taken with the Tamron. Hope the images are still available.

-Veijo-

--
He hath made every thing beautiful in his time... Eccl. 3:11

Check my photogallery at http://www.kolumbus.fi/veijo.matikainen/Galleriat/PoD2008/PoD.html

Thanks for reply!

I'm tempted by sigma for the price (ebay: sigma 249 euro, tamron 320 euro), 24mm and tamron for colour and cotrast.
Hard choice!

nero501 said:

Thanks for reply!
I'm tempted by sigma for the price (ebay: sigma 249 euro, tamron 320
euro), 24mm and tamron for colour and cotrast.
Hard choice!

Click to expand...

To make it even harder, I'm waiting for the new Sigma24-70/2.8 with silent/fast HSM focusing. It will be more expensive though than the two other options...

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Tom - http://www.pentaxphotogallery.com/tomvijlbrief

Same for me. I have the Tamron SP 28-75/2.8 and love it. It's an excellent lens at a good price.

In fact, it was my favourite lens until I got the Pentax DA* zooms, but they are in a different price range. In terms of IQ, there is not a great difference between the three of them, but the Tamron is not weather-sealed and relies on the screw-drive for focussing. The Tamron's zoom range overlaps both of the DA* zooms, which I find very useful, as I can avoid lens changes by picking the appropriate zoom.

--

Horses are good subjects for photography, but terrible platforms for a photographer.

I worked recently with a friend's Tamron 28-75. Very nice lens, but it had a seeeeeerious frontfocus, I had to adjust my K10D to -200 to get decently focused image. And it was a nasty, curious sort of fronfocus, because it depended on the distance. That means that for for closer subjects (under one meter distance) a focus correction of -150 was enough, while for distanced objects (more that 10 meters) the correction needed was somewhere at -250. I picked -200 as a middle value and got pretty decent shots at a conference, with quite wide apertures (F3.5 - F4.5), in a variety of situations (close subjects, distanced subjects, etc).

Therefore, I would suggest to pay attention also to return policies, to be able to change the lens if it's not working properly, or to take your money back.
I know absolutely nothing about similar issues in Sigma.
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Comments, criticism, suggestions: it goes without saying!
http://s86.photobucket.com/albums/k107/huzururmuz/

Here's one i took...



k10d, sigma 24-60 @ f 2.8, sigma 530 dg super on cam -1ev

VaLeX said:

I worked recently with a friend's Tamron 28-75. Very nice lens, but
it had a seeeeeerious frontfocus, I had to adjust my K10D to -200 to
get decently focused image. And it was a nasty, curious sort of
fronfocus, because it depended on the distance. That means that for
for closer subjects (under one meter distance) a focus correction of
-150 was enough, while for distanced objects (more that 10 meters)
the correction needed was somewhere at -250. I picked -200 as a
middle value and got pretty decent shots at a conference, with quite
wide apertures (F3.5 - F4.5), in a variety of situations (close
subjects, distanced subjects, etc).

Click to expand...

I used to have a 28-75 too, it behaved a bit funny when it came to focus accuracy, to me it seemed like focus shift when stopping down. Another thing, even if it was very sharp on close to medium distances, it was never very impressive on more distant subjects.

Could you explain how ou adjust a K10D autofocus to correct for frontfocus? One of the advantages of stepping up to the K20 from the K10 was the ability to adjust AF in the 20, something lacking in the 10.

Is there a feature of my K10D I should know about?

VaLeX said:

I worked recently with a friend's Tamron 28-75. Very nice lens, but
it had a seeeeeerious frontfocus, I had to adjust my K10D to -200 to
get decently focused image. And it was a nasty, curious sort of
fronfocus, because it depended on the distance. That means that for
for closer subjects (under one meter distance) a focus correction of
-150 was enough, while for distanced objects (more that 10 meters)
the correction needed was somewhere at -250. I picked -200 as a
middle value and got pretty decent shots at a conference, with quite
wide apertures (F3.5 - F4.5), in a variety of situations (close
subjects, distanced subjects, etc).

Therefore, I would suggest to pay attention also to return policies,
to be able to change the lens if it's not working properly, or to
take your money back.
I know absolutely nothing about similar issues in Sigma.
--
Comments, criticism, suggestions: it goes without saying!
http://s86.photobucket.com/albums/k107/huzururmuz/

Click to expand...

--
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We cannot photograph our own emotions.
http://web.me.com/lawsonstone1
http://www.flickr.com/photos/lawsonstone/

to cut a long story short, you have to access the debug mode - but you'll be able to make only one focus adjustment and save the setting. The modification you'll make will apply to any lens you put on the camera.

For detailed info, check these:
http://photographyrulez.blogspot.com/2008/06/k10d-focus-error-adjustment.html
http://www.rarwebworks.com/Photography/Pentax.htm

Later edit:

Here you can find a software for accessing debug mode through USB, no matter what firmware you use on a K10D:
http://www.rarwebworks.com/Photography/PentaxLinks.htm
--
Comments, criticism, suggestions: it goes without saying!
http://s86.photobucket.com/albums/k107/huzururmuz/

Snigelben said:

I used to have a 28-75 too, it behaved a bit funny when it came to
focus accuracy, to me it seemed like focus shift when stopping down.
Another thing, even if it was very sharp on close to medium
distances, it was never very impressive on more distant subjects.

Click to expand...

Interesting information, someone say if the sigma is not sharper at long distant?

One was totally out of focus at 75. One was really badly BF'd at 28. The last was BF'd at 75.

If Pentax adds a focus correction curve so you can specify the amount of BF/FF correct at different focal lengths, it might help Tamron 28-75 users. A simple straight line between control points for adjustment would work ok but being able to specify a curve would be better probably. Tamron really should fix this "feature" though. Sounds like some of the Tamron 70-200/2.8 copies also have this issue...

I'm waiting for the new Sigma 24-70/2.8 HSM to show up early next year before deciding whether I want to go back to Tamron roulette

I can only speak to the Tamron 28-75 lens. It is a good one. But when I returned from a trip in which I only carried it and a Pentax prime, the difference in results between the two was so telling that I sold the Tamron and have since purchased two more Pentax primes. This may not be helpful, but it is my personal experience/preference.

Good luck,
Michael

It is the first lens I bought for my Pentax dSLR and probably I use it most often, even now that I have good collection of primes.
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-Dominik

I really like the Sigma 24-60mm f2.8, though I use it in a different mount.

The only thing I don't like about it is that it isn't F1.4.

I'd be more concerned with the camera's AF. After all it is the camera not the lens that decides where the focus point is. If the camera doesn't like the focus point it should keep trying. If it doesn't then the camera thinks it is in focus.

This is a problem that is cropping up more and more as the pixel density of the cameras has increased. This was never an issue during the film days nor in the days of 6 MP cameras only.

People think it is easy just to pick on the lens when the lens has nothing to do with picking the focus point.

Reason why tech support likes to get the lens and camera is mainly, one, to see if the lens is in specs and two to adjust the camera's AF system by using that lens.

And the issue about focus points varying with subject distance has been cropping up with all brands, even Canons using pro "L" lenses.

That is why they are all putting AF micro adjustment in the cameras so they don't get as much people sending things back to "fix".

Correct focus point should be 1/3rd from front of range and 2/3rds from back of range. Not in the middle as that is incorrect. But as the pixels go up the actual range of acceptable focus shrinks due to lens limitations.
Kent Gittings

I can't really speak about the sigma,because I haven't used it, but the tamron is a fantastic lens. It has great contrast and bokeh, and I find it pretty sharp from wide open at all focal lengths. In short I don't find myself avoiding any apertures or focal lengths. I found it makes a great pair with the DA 12-24mm

A few Samples:

1/15s f/2.8 @ 55mm & ISO 400 on K10D



1/125s f/3.5 @55mm ISO200 K10D



1/80s f/7.1 @28mm ISO100 K10D



1/160s f/4.5 @43mm ISO200 K10D



1/80s f/7.1 @55mm ISO200



1/200s f/7.1 @63mm ISO200



--
Craig
http://www.flickr.com/people/craigjewell/

Thanks for the answers. Finally i have buy a Tamron 17-50 f/2.8 from Japan (ebay) for 280 euro ( shipped ).
Later post some pic in comparison with 18-55 da end fa 50.

nero501 said:

Finally i have buy a Tamron 17-50 f/2.8 from

Click to expand...

good to know what you decided.
if you have only one lens, i think the lens you selected is a better range.

of the two you were considering, i think the Sigma is not wide enough for one lens. i feel like i would want to buy another lens, too, that would be wider.