[outsider]

Does anyone know what the sharpest focal length is for the tamron 70-200 2.8 macro? I usually shoot portraits at about 135-160, but am afraid of going much past for fear of softness and distortion.

[JinDesu]

Sharpest focal length of the 70-200 is 70-125 I believe. I have ridiculously sharp shots at that focal length. For portraits, I have used it for a few shots in the 100-150mm range and it's great at F2.8. Stop down to F4 and poof, pure magic.

Supposedly 135mm is the weakest, then it gets better again between 135-200. Some full sized photos from my k-x below...

http://farm8.staticflickr.com/7066/6845298028_72f6bffc49_o.jpg - 70mm
http://farm8.staticflickr.com/7202/6887737360_96f5acc96d_o.jpg - 80mm
http://farm8.staticflickr.com/7235/7075585957_9dbd812db3_o.jpg - 90mm
http://farm8.staticflickr.com/7165/6833351655_6a7efd614c_o.jpg - 115mm
http://farm7.staticflickr.com/6227/6281465105_ee1695e764_o.jpg - 140mm (F4)
http://farm7.staticflickr.com/6118/6281980698_5f9531bb07_o.jpg - 170mm (F4)

[SpecialK]

You could do some test shots with your copy and look for the elusive differences :-)

[chickenandavocado]

stop down to f/4 on this lens and i find all FL's are good performing!

[Marc Sabatella]

Just because a lens is X% sharper at one focal length than another doesn't mean it suddenly becomes useless outside of its sharpest range. This is a professional quality lens, used by professionals at *all* focal lengths.

[outsider]

Just because a lens is X% sharper at one focal length than another doesn't mean it suddenly becomes useless outside of its sharpest range. This is a professional quality lens, used by professionals at *all* focal lengths.

Obviously I didn't say it was useless because of a less performing range. I just wanted to see if anyone knew of the optimal range (which there probably is for all copies), so I could make the most of the lens for my portraits.

[Marc Sabatella]

I was respnsng to the notion that you avoid certain focal lengths. Takng a pciture at the wrong focal length - and thus getting a composition other than you wanted (either because sibject size is wrong, or perspective is wrong) just to avoid a slight reduction in sharpness makes no sense. That,s like looking for your dropped cars keys on the wrong side of the street because the light is better.

[Ash]

I agree with Marc on this one. It is unhelpful information to know where the 'sharpest' and where the 'least sharp' focal lengths are on the lens.
There were reports on 135mm being the 'weak point' of the Tamron 70-200, but few real world shots that support it.
I have a number of 135mm shots at f/2.8 that are just excellent.

[joe.penn]

That,s like looking for your dropped cars keys on the wrong side of the street because the light is better.

But with more light wouldn't it be easier to find your keys


EDIT: BTW, not sure where the 135mm "not good" comes from, according to the MFT charts 135mm shows the strongest center sharpness across f/stops. The chart is for a canon sensor but it has to be somewhat relative -> http://www.photozone.de/canon-eos/576-tamron70200f28apsc?start=1

[Ash]

No Joe - no matter how much light you have, you won't find the keys if you're not looking for them in the right place.

And this is where I got the 135mm data from:
Tamron SP AF 70-200mm F2.8 Di LD (IF) Macro review: Digital Photography Review

It is the Canon mount version that was tested, but it is optically the same lens. You can check the striking difference in figures given by the DPreview group by using their MTF-50 test curve.
"A generally impressive performance, let down only by some softness wide open in the middle of the zoom range (particularly at 135mm)."

[Sage97]

stop down to f/4 on this lens and i find all FL's are good performing!

I'll try this later today. Thanks.