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06-19-2011, 09:15 AM   #1
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What causes this haze/softness/blowout on Tamron 70-200mm?

I've been trying out my new K-5 and Tamron 70-200 F2.8 combo and I'm really annoyed at the performance at F2.8. Photos are hazy/soft/blown out (see example below). This is my second copy of this lens (the first was sent back because it front focused too much for the K-5 to compensate for it), and both showed this effect equally.

First, is this to be expected of this lens at F2.8, or is it something I'm doing wrong? I have an old vivitar 200mm f3.5 k mount lens and, while it exhibits this, it's not near so bad.

Second, what can I do to minimize or eliminate this effect if it's the lens or camera? There are times that I'd really like to take advantage of the lens wide open to minimize depth of field.

The attached photo has a 100% crop from two images. The left is 200mm, F2.8, ISO 125, 1/250sec. The right is 200mm, F4, ISO 160, 1/250sec. Distance is about 5ft, lens hood is on, it's a cloudy day. I simply dialed F2.8, took the first shot, dialed F4.0, and took the second.

Thanks,

Attached Images
 
06-19-2011, 09:36 AM   #2
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I think it's just overexposed. What mode are you using?

06-19-2011, 09:49 AM   #3
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I'm using Hyper-Program mode.

I figured that there was an element of overexposure there, but it's pretty darn consistent if so. Flowers, trees, signs, brick walls, etc. all consistently show the haze, softness, and bad washout at F2.8. The washout is particularly annoying of course.

I'll try some shots with varying degrees of exposure compensation and see what happens. It'd suck to have to adjust that every time I or the camera set the aperture to F2.8, but I guess that would beat not being able to do anything about it.

Anyone else experience this with this lens/camera combination?

EDIT: I tried repeating the shots with varying degrees of exposure compensation. It helped with the blowout, but by the time the blowout was gone the rest of the photo was too dark to be usable. I could not achieve a photo that approached anything like the F4 photo for overall exposure quality. It's more than just the camera getting the exposure incorrect when the lens is wide open.

Last edited by KyPainter; 06-19-2011 at 10:08 AM.
06-19-2011, 10:09 AM   #4
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When shooting flowers, I pick one of the semi auto modes (Av or Tv) and set EV comp to about -1 with auto ISO. It sometimes means I have to bring it up a bit in post processing but I generally avoid having everything blown out that way (and I use Spot metering almost exclusively).

2011 in Bloom - a set on Flickr

I've found when left to its own devices, the K5 tends to overexpose to begin with.



06-19-2011, 11:06 AM   #5
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Well, I took quite a few photos at F2.8 and F4 with different degrees of exposure compensation. Duplicated the photos with this lens on my K10d. Then I did the same using the old vivitar lens wide open and closed 1 stop. Everything is good, it's primarily an exposure issue.

It sure confuses the hell out of me though. I can put my Sigma 18-50 F2.8 on either camera, take photos of the same flowers, lens wide open, close enough to give the same photos, and never wash out the photos like that. Tried it. Blow some highlights for sure, blow the red channel in spots, but completely wash them out... not in a dozen deliberate tries and rarely that I can recall. Ditto with my Tamron 70-300 F4-5.6 macro or other slower lens.

Is there something different about longer, fast, lenses that makes this more prone to happen?
06-19-2011, 11:26 AM   #6
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I don't know. I'm out of ideas on that point. The longest zoom I used was the 50-135 Pentax.You're saying it does this with both the K10d And the K5? I must have missed that point. While the K5 tends towards overexposure IMO, the K10d always underexposed. Since you can take normal photos with your other lenses, I, like you, would have to question the 70-200.

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