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03-06-2012, 10:49 AM   #1
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Should I upgrade my 28-70 EX DG Sigma?

This post will show my absolute ignorance of the limits of a mid range zoom, especially with regards to sharpness, so I am relying on this community's brilliance and kindness to guide me. I shoot portraiture, and I just feel unhappy with my Sigma. I really only use it to get a bit more width when shooting in studio, and have toyed with picking up a 35 prime to replace it. But, for fashion, I do like having a bit of space between myself and the subject, and I would really like to know if there is a better mid range zoom out there. I'm willing to pay for it. Maybe not $1300, but up to $900-ish.

I do want to say that I get such stellar images with my 50mm 1.7, and I know that comparing the two is like comparing apples and alligators. But, seriously, can I get closer to the sharpness of the 50 with a zoom? Any closer at all?

Thanks for any advice.

03-06-2012, 11:13 AM - 1 Like   #2
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You might want to take a look at the Tamron 28-75mm and 17-50mm lenses. They can both be picked up fairly cheap off the marketplace here and they both have reputations for being quite sharp in IQ!

Also, you might take a look at the Sigma 24-70mm EX HSM lens. I hear it's better than the one you say you have.

Or what I might suggest if you're willing to pay around $900, is to get the Tamron 17-50mm and the Pentax DA* 50-135mm. You'd have a nice range covered then and fantastic IQ at that!

Just some thoughts...
03-06-2012, 12:10 PM   #3
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Thank you for your thoughts. I will check out the Tamron 28-75 as you suggest. I know there are at least several well respected photographers here who use that fairly extensively, and that recommends it to me as well. The Pentax 50-135 is on my list, but more for weddings than studio where I need something to cover the wide end. Thank you again!
03-06-2012, 12:12 PM - 1 Like   #4
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Have you calibrated your lens to your camera?

I own the newest versions of the non-OS 24-70 EX HSM and 70-200 EX HSM II and wasn't too thrilled with them out of the box. I attempted in-camera calibration as I did with my DA*16-50, but there wasn't enough calibration available that would work for the two Sigma lenses.

So I sent both lenses to Sigma (along with one of my Pentax bodies) for calibration. What a difference did that make!

Calibration might be worth looking into before dropping money on a replacement lens. Instead, you can then buy a prime lens or a wide-zoom and add to your arsenal.

03-06-2012, 02:13 PM   #5
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the Tamron 28-75 is being replaced by a new model later this year so you may want to wait!
03-06-2012, 02:37 PM - 1 Like   #6
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What conditions are you shooting with? Are you shooting in studio, F8? Or wide open?

The Tamron 28-75 will do MUCH better than the Sigma 28-70 at 28mm wide open. Stopped down, they both perform similarly with the Tamron doing better at all focal lengths and aperture. The Sigma (and Tamron) 17-50 will do better than the Tamron 28-75 at 50mm or so, but at 28 they are equal.

So, with all that in mind, if you are shooting F8, none of them should be THAT much better than your current Sigma. And none of them really compare that well vs a good 50mm prime at the same aperture.

So if you shoot wider, the Tamron is better than your Sigma. If you shoot at 50mm, the 17-50s are better than your Sigma.
03-06-2012, 03:38 PM   #7
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QuoteOriginally posted by kmwsbabe Quote
Thank you for your thoughts. I will check out the Tamron 28-75 as you suggest. I know there are at least several well respected photographers here who use that fairly extensively, and that recommends it to me as well. The Pentax 50-135 is on my list, but more for weddings than studio where I need something to cover the wide end. Thank you again!
That is why I suggested the Tamron 17-50mm as well to cover the wide side.

QuoteOriginally posted by Franky2step Quote
the Tamron 28-75 is being replaced by a new model later this year so you may want to wait!
I hadn't heard that before. Do you know for sure that it will replace the current Pentax one? Because with the 17-50mm they released the second edition with USD (or whatever the AF motor is called for Tamron) or was that VC? but Pentax didn't get it.
03-06-2012, 03:47 PM - 1 Like   #8
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Tamron -Tamron develops world's first*1 full-size, high-speed standard zoom with built-in image stabilization - SP 24-70mm F/2.8 Di VC USD (Model A007)

looks like Pentax has been excluded

03-06-2012, 05:18 PM   #9
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George, the calibration is a great idea. I would expect it would matter which body was sent, though. Is this an incorrect assumption? Because I can't really do without my k5, but I could send in my k-x.

JinDesu, I do tend to shoot wide open when I need the light. And it's typically around the 30-35mm focal length. However, even when I strobe, working with f8 and a tripod, I still don't feel the images are a sharp as they should be. But, I know I am unfairly comparing it to my 50, and there is no way they can compare. So, I went ahead with a 35mm purchase today. Just the cheapie 2.4 since it has predominantly good reviews, and it will be about a year before I can drop $1300 on a lens. And I am still highly considering the Tamron version, since this is a great zoom range for fast toddlers.

Ubuntu_user, thanks for the recs. I get where you are coming from on the 2 lenses. They are a bit out of my current budget together, but the 50-135 is definitely on the wish list.

I really appreciate all the thoughtful advice from everyone. It has been very helpful! Thank you so much!
03-06-2012, 10:56 PM   #10
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It would matter which body you send. In my case, my K5 and K20 are the same when it comes to lens calibration. When I calibrate my 16-50 on one, I end up doing the same to the other with good results. In my case, I sent my K20 as the K5 is my primary.

When the lenses got back, I did more testing using the K5, and with zero adjustments they were spot on.

They also upgraded the firmware on the lenses, which included the AF data). As a bonus, now both lenses are properly identified in Lightroom :-D
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