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01-10-2011, 08:39 AM   #16
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QuoteOriginally posted by Jewelltrail Quote
It is true that the 28-75 handles vignetting better than its sibling due to being Full-Frame. However, it is not true that the 28-75 has better edge to edge sharpness than the 17-50, even though you enjoy are using a lens designed for FF in the case of the 28-75.

Actually, the 2 lenses perfrom very similarly, edge to edge. See, for example, Photozone's MTF charts for the Nikon copies. The closest you can get to a direct comparison, is the 35mm focal range of the 17-50 vs the 40mm focal range of the 28-75. Look at these charts and see what you think. Of course, these charts do not mean your copy of the 17-50mm performs the same. However, from what I can see with my 17-50 & 28-75, the 17-50 enjoys the sharpness edge in just about all situations.
You could be right about the edge to edge sharpness, and both lenses do produce excellent results in this regards. As far as sharpness wide open, if the 17-50mm truly does have a max aperture of only f/3.3 or f/3.4 (as I suspect), then it would be cheating in the sharpness game and direct comparisons at wide-open would not be fair.

01-13-2011, 10:07 PM   #17
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Holy Toledo, I just looked through the Tammy club shots and my jaw dropped at the sharpness. I really want one now! Have to say that I am attracted to the wide angle shots, causing more indescision. this problem with the 17-50 sounds like a deal breaker though. any thoughts about an alternative for the 17-50?
01-13-2011, 10:44 PM   #18
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QuoteOriginally posted by Genshu Quote
Holy Toledo, I just looked through the Tammy club shots and my jaw dropped at the sharpness. I really want one now! Have to say that I am attracted to the wide angle shots, causing more indescision. this problem with the 17-50 sounds like a deal breaker though. any thoughts about an alternative for the 17-50?
Even with the aperture problem, the Tamron 17-50mm is still a good lens, and for the price it's hard to beat as a direct replacement for the kit lens.

As far as an alternative, Sigma just released a new 17-50mm f/2.8. The few reports I've read of it are very positive, and it appears to have better image quality than the Tamron.

Another big advantage is that it has a silent and fast HSM focus motor, whereas the Tamron uses the screw-drive for focusing.

And the Sigma even has OS. Probably kind of redundant since Pentax has stabilization in the body, but Sigma's OS is supposed to be very good and may out-perform Pentax's OS. It would also allow you to see the effects of stabilization when looking through the viewfinder, which might be nice.

The only bad thing is that the Sigma costs about $200 more than the Tamron. The Tamron sells for around $460, while the Sigma is selling for $670.
01-14-2011, 07:07 AM   #19
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QuoteOriginally posted by Genshu Quote
Holy Toledo, I just looked through the Tammy club shots and my jaw dropped at the sharpness. I really want one now! Have to say that I am attracted to the wide angle shots, causing more indescision. this problem with the 17-50 sounds like a deal breaker though. any thoughts about an alternative for the 17-50?
A to full stop underexposure is easily compensated for, regardless of what exposure mode you are using. Shoot Av and add compensation, shoot manual and do it yourself. No biggee, you know about it and you dial it in (compensation) when you put the lens on the body.

Many of my Tamron lenses underexpose compared to other lenses. It is what it is, adapt or use something else.

Get the 28-75 first, it's better for portraits. Replace the kit lens with the 17-50 later. And yes, I have both lenses, and I got them in that order. The 28-75 was my main lens for almost 4 years. A Pentax 18-35 handled my wide angle stuff. Now the Tammy 17-50 does that.

01-14-2011, 09:49 AM   #20
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QuoteOriginally posted by bimjo Quote
A to full stop underexposure is easily compensated for, regardless of what exposure mode you are using. Shoot Av and add compensation, shoot manual and do it yourself. No biggee, you know about it and you dial it in (compensation) when you put the lens on the body.
Of course you can compensate for it, but the fact of the matter is that you're dealing with a smaller aperture, and everything that entails.

That means that for any given f-stop, you will have to use a slower shutter speed than you otherwise would. And that means that you are more likely to get motion blur from a moving subject, and/or soft pictures due to camera shake.

You also have less control over depth of field, since you will not have the same shallow depth of field at f/3.3 as you would at f/2.8.

So it's true that you can dial in compensation, but it's also true that you're missing out on the full advantages of a true f/2.8 lens. The lens simply doesn't capture as much light as it should.
01-14-2011, 10:48 AM   #21
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If it is mainly for photographing people, I would agree that the 28-75 would be the better choice (with the kit lens for when you want a wider lens).

Regarding the thought that you had to get the 28-75, because of possible problems with the 17-50, you might also want to consider the Sigma 18-50.

However, I think I would say go for the 28-75.
01-14-2011, 06:13 PM   #22
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QuoteOriginally posted by Edgar_in_Indy Quote
Of course you can compensate for it, but the fact of the matter is that you're dealing with a smaller aperture, and everything that entails.

That means that for any given f-stop, you will have to use a slower shutter speed than you otherwise would. And that means that you are more likely to get motion blur from a moving subject, and/or soft pictures due to camera shake.

You also have less control over depth of field, since you will not have the same shallow depth of field at f/3.3 as you would at f/2.8.

So it's true that you can dial in compensation, but it's also true that you're missing out on the full advantages of a true f/2.8 lens. The lens simply doesn't capture as much light as it should.
I'm curious- did you ever up the ISO settings to preserve shutter speeds? Can't argue DOF, assuming the lens is actually stopping down farther than it advertises. But I do have to think that if DOF is so critical that stop will ruin the shot you'd be shooting a faster lens than a f/2.8 zoom anyway.
01-15-2011, 12:31 AM   #23
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What a great site. Leaning for the 28-75, like the idea of gettin another wider one sometime later. $600 somethin for a lense right now is outta the question for me. regarding lense speed 2.8 is about as fast as I would want to go. dont see much use in those 1.4 somethings with a dof where a face is in focus but the nose is not!

01-15-2011, 03:45 AM   #24
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I would agree with others on the EV compensation. I currently use the 17-50,28-75,70-200 and 90 and adjust the EV control with them and my Simga and Pentax lens regularly. I have had to use Tamron service department(warranty) twice and they will address any and all issues you may have with their product.
Mike
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