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Archive 2005 · Tamron 28-75 Focus Issues

  
 
steve_t
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p.3 #1 · p.3 #1 · Tamron 28-75 Focus Issues


saaketham wrote:
...Did you try shooting with higher ISO. I got sharper images at f/2.8 when shooting at ISO-400.

That's camera shake, not lens sharpness (higher ISO = faster shutter). Lay off the coffee for a bit.



May 25, 2005 at 12:20 PM
saaketham
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p.3 #2 · p.3 #2 · Tamron 28-75 Focus Issues


steve_t wrote:
That's camera shake, not lens sharpness (higher ISO = faster shutter). Lay off the coffee for a bit.


I don't drink more than 2-3 cups of coffee a week or so.
As for the shake, I was shooting on a tripod, with remote release and mirror lockup, indoors, taking pictures of a static, inanimate subject, at both low and high ISOs. What more could I do to reduce shake?



May 25, 2005 at 01:04 PM
Jkan2001
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p.3 #3 · p.3 #3 · Tamron 28-75 Focus Issues


saaketham wrote:
They all look horribly soft. Just like the Tamron 28-75 and Sigma 24-70 I recently bought on Buy & Sell. By f/4, images are much sharper and f/5.6, it's great. f/8 seems to be the sweet spot. Did you try shooting with higher ISO. I got sharper images at f/2.8 when shooting at ISO-400.


On those particular test images I shot ISO 100, it was too bright outside to use 400. Anyways, the shutter speeds were well over 1/150th so I imagine it wouldn't make a technical difference. The lens does sharpen up quite a bit at F4 and it's very good by F5.6. I guess it's just not a wonder lens @ F2.8.

I can't decide if my case is normal or to send it back and demand it be calibrated till it's sharp @ F2.8



May 25, 2005 at 02:08 PM
saaketham
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p.3 #4 · p.3 #4 · Tamron 28-75 Focus Issues


I've read of many owners claiming "mine's incredibly sharp at f/2.8". But, when asked for 100% crop, sharp samples at f/2.8, nobody posts anything. Instead, some post sharp images at f/4 or narrower. These are 100% crops, no sharpening, only contrast adjusted. The links show actual image sizes.
- At f/4
- At f/4
- At f/11
- At f/2.8

http://i.pbase.com/u26/saaketham/large/43868673.1.jpg
http://i.pbase.com/u26/saaketham/large/43868833.2.jpg
http://i.pbase.com/u26/saaketham/large/43868838.3.jpg
http://i.pbase.com/u26/saaketham/large/43868843.4.jpg



May 25, 2005 at 02:47 PM
Jkan2001
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p.3 #5 · p.3 #5 · Tamron 28-75 Focus Issues


saaketham wrote:
I've read of many owners claiming "mine's incredibly sharp at f/2.8". But, when asked for 100% crop, sharp samples at f/2.8, nobody posts anything. Instead, some post sharp images at f/4 or narrower. These are 100% crops, no sharpening, only contrast adjusted. The links show actual image sizes.
- At f/4
- At f/4
- At f/11
- At f/2.8

http://i.pbase.com/u26/saaketham/large/43868673.1.jpg
http://i.pbase.com/u26/saaketham/large/43868833.2.jpg
http://i.pbase.com/u26/saaketham/large/43868838.3.jpg
http://i.pbase.com/u26/saaketham/large/43868843.4.jpg


It looks like you got a really sharp copy, it looks decent even at F2.8. I should definetely do some F4+ shots to compare. What ISO/shutter speed were these taken at?

Also for a 100% crop did you just randomly crop what you thought was the middle and save the file or is there a better way to post a 100% crop?



May 25, 2005 at 04:11 PM
steve_t
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p.3 #6 · p.3 #6 · Tamron 28-75 Focus Issues


saaketham wrote:
I've read of many owners claiming "mine's incredibly sharp at f/2.8". But, when asked for 100% crop, sharp samples at f/2.8, nobody posts anything. Instead, some post sharp images at f/4 or narrower. These are 100% crops, no sharpening, only contrast adjusted.

Them's fightin words. Here's a quick test of the Tamron @28mm and F2.8 through F5.6
Tripod mounted, ISO 100 & MLU enabled, best of three each on a 350D.
http://www.pbase.com/sp_todd/image/43874337/original
Usable at F2.8 I think you'll agree.



May 25, 2005 at 05:44 PM
Jkan2001
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p.3 #7 · p.3 #7 · Tamron 28-75 Focus Issues


steve_t wrote:
Them's fightin words. Here's a quick test of the Tamron @28mm and F2.8 through F5.6
Tripod mounted, ISO 100 & MLU enabled, best of three each on a 350D.
http://www.pbase.com/sp_todd/image/43874337/original
Usable at F2.8 I think you'll agree.


Judging from your pics I think i've come to notice that almost all the lenses are pretty sharp @ F2.8-F4 when it's an up close shot within 5 feet or so. When I shoot the box the lens came in i'm not too dissapointed @ F2.8 and i'm actually happy with F4, however when I go outside and shoot something 100 feet away F2.8 it's another story.



May 27, 2005 at 04:34 PM
RDKirk
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p.3 #8 · p.3 #8 · Tamron 28-75 Focus Issues


[Judging from your pics I think i've come to notice that almost all the lenses are pretty sharp @ F2.8-F4 when it's an up close shot within 5 feet or so. When I shoot the box the lens came in i'm not too dissapointed @ F2.8 and i'm actually happy with F4, however when I go outside and shoot something 100 feet away F2.8 it's another story.


Is that an autofocus issue or an optical issue? What are the results when you focus manually?



May 27, 2005 at 06:23 PM
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