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02-26-2013, 05:10 PM   #1
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Soft at f2.8

Just a question. Have struggled getting quality images with my month old Tamron 70-200 at f2.8 . After reading the forum reguarding focus adjust I set up a test . K-30 tripod mounted shake reduction off aperture priority. Focused from nearest point set in manual switched to auto select point to focus and used 2 sec delay for shutter outside in overcast light from about 12 ft away and square to focus point . Adjusted focus to a -4 and at 2.8 seems very soft . At f4 sharpens up considerably. My question is this acceptable softness from this lens ? Why buy a 2.8 if the images are unuseable at 2.8? I have had good results at f4 and higher . Any comments from Tamron users will help calm my LBA remorse!

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02-26-2013, 05:21 PM   #2
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24 looks to be in better focus than 22. If 22 is the focal plane of the paper then you need to adjust the focus backwards.
02-26-2013, 05:25 PM   #3
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22 is the focal plane . I thought this was considered front focus and required a minus adjustment . What do you think about the sharpeness at 2.8?
02-26-2013, 05:51 PM   #4
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We adjust the focus like this: 0 first,+2, +4, +6, then -2, -4, -6. Look at this pics and pick the best one and re-set the camera for that focus and re-do the pic that was sharpest to make sure it still looks the best, or bracket again in 1 increments. BTW, that lens is one we have and it is a little glowey at F2.8 and 200mm but gets a lot better at F4, and we love that lens and use it all the time. YMMV,

David

02-26-2013, 06:07 PM   #5
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Glowey is a good description of some of the results . Just want to make sure its common with this lens . I know it is not super expensive but I want to make sure it is not a bad copy . I have posted before but the bad weather up here has limited my use and produced some less than perfect results.
02-26-2013, 06:12 PM   #6
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I'd just take the shot in manual focus to determine if it's soft or not. Adjusting focus is more for checking if your thing hits focus or not. That being said, here is a series of full resolution sample shots on my k-x for you to review:

Tamron 70-200 F2.8:
@200mm F2.8 unprocessed - http://farm9.staticflickr.com/8372/8511976984_b89e0d8960_o.jpg
@200mm F2.8 processed - http://farm9.staticflickr.com/8509/8510864989_273ae95cd9_o.jpg

@200mm F2.8 unprocessed - http://farm9.staticflickr.com/8375/8510864695_8c93b7932f_o.jpg
@200mm F2.8 processed - http://farm9.staticflickr.com/8379/8510864465_f1e0532d95_o.jpg

@200mm F4 unprocessed - http://farm9.staticflickr.com/8375/8510864695_8c93b7932f_o.jpg
@200mm F4 processed - http://farm9.staticflickr.com/8532/8510864041_007f1776ef_o.jpg

As you can see, once processed, F2.8 is pretty reasonable. It can be glowey - as David said, and I attribute that partly to the hood. The hood is designed for 70mm so it doesn't vignette, but that means it won't fully cover 200mm. This means there can be quite some amount of angled lighting causing the image to lose contrast.

With all that being said, my lens is much much sharper in the 70-135 range, and still very sharp in the 135-170 range. Once I go to 170-200, it becomes softer.
02-26-2013, 06:22 PM   #7
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I took a few shots from about 50ft away tripod mounted and the focus seemed better .
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02-26-2013, 06:29 PM   #8
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Use CDAF focus - ie live view, to eliminate focusing issues from your investigations about the lens. CDAF is a lot more accurate (but slower).
Also, do these outside in daylight. Artificial light has not got the complete colour spectrum, so getting your focus right under artificial light will mean your lens will be incorrectly adjusted for daylight.

Also, I would bet that the lens were correctly adjusted in the factory and it's best to leave focus adjustment at zero. The factory tests are likely to be better than what you can carry out at home with cardboard boxes. So unless your lens has been dropped - assume it's already correctly adjusted!

--
edit - I see you posted as I was typing.
The outside shots prove my point I think, about artificial light.

02-26-2013, 06:50 PM   #9
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Both tests done outside today with overcast sky at 3:30 pm DST
02-26-2013, 07:25 PM   #10
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There has beeni a lot of discussion over the years about tamron and sigma 70-200/2.8 lenses and changes to the optical design and sharpness wide open at F2.8

Of all the lenses, I think the Sigma APO 70-200/2.8 EX non DG non macro is the sharpest wide open at 200mm and 2.8 which is why I have never "traded up"
02-26-2013, 07:54 PM   #11
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Is there a way to see the full-size image? I don't know how anybody can comment much on sharpness without seeing the full size image.
02-27-2013, 08:53 AM   #12
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I can upload a full image . Which one would be better?
02-27-2013, 10:12 AM   #13
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I suppose the test chart at f/2.8 would be the one to upload in full-size. And if you took that picture using autofocus, then you may want to take another one, this time focusing manually with maximum magnification in live view. That way we know that any softness is caused by the optics, and not by any autofocus inaccuracy.
02-27-2013, 11:28 AM   #14
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Full image of test grid and tree bark test. It is pouring rain here today so another test shot with live veiw in day light might have to wait .
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02-27-2013, 12:18 PM   #15
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The images you just posted are only 1208x800, or about 1 megapixel. Maybe it's not possible to post full size images using the forum image tools. I'm not sure, because I never use them. I always host my images on my own server space.

Last edited by Edgar_in_Indy; 02-27-2013 at 02:43 PM.
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