Did I get a sharp Tamron 28-75/2.8?

[pablo_s]

After reading the great reviews (including Bob Atkins') I decided to

replace my EF 24-85/3.5-4.5 lens by the Tamron 28-75/2.8. I bought

it used locally. Since some people say they got a soft version of

this lens, I did a few tests to check whether that was the case with

mine.

 

It seems to be a little bit softer than the 50/1.8 at 50mm... on one

hand this is not too surprising; in fact, it's surprising that it

comes so close to one of Canon sharp primes. But Bob says the Tamron

is at least as good as the Canon if stopped down, and that doesn't

seem to be the case with mine. I'm attaching 100% crops of the

center, shot at f/5.6. First the Canon.<div></div>

[pablo_s]

Now the Tamron. Notice that even though the shot was taken at 50mm (confirmed by EXIF data), the actual forcal length seems to be less, since the crop is smaller and the area represented is the same. Do you know what may be going on?

 

Thanks in advance!<div></div>

[shawngibson]

What was your focusing distance from the subject? I'll perform a similar test and post you the image I get if you want...but I don't have the 50, only the Tamron...

 

Shawn

[shawngibson]

...also was it RAW, or what jpeg settings, anything in Photoshop etc...?

[shawngibson]

...and what camera might help:(

 

Sorry, just woke up...

[panos_voudouris]

The focal length will be slightly different if you are not focused to infinity. This is also true for the prime but different lenses lose different amounts depending on the design.

[shawngibson]

I never focus to infinity, actually, as I'm always trying to get some background blur. That said, if you are curious to compare with my version, gimme the test condifions (I've a tripod and a remote) and I'll post what I get...just for fun, and to be a nice neighbour:)

 

Shawn:)

[sean_mclennan]

well, I own both these lenses myself, at F8 I *cannot* tell the difference in clarity/sharpness between the two at anywhere between 40 to 60mm on the Tamron...at either far ends on the Tamron, I do notice a small difference, mostly in the edges of the photo.

 

At F5.6, I find them very close and often have to really look hard to spot the difference, again, mostly outside the center of the photo.

 

Once I stopped worrying about these 100% inspections and just started shooting...I honestly can't tell which lens I used for which shot unless I look at the Exif data (if I shot the Tamron close to 50mm)or it was very low light condition or very high bokeh.

 

For what it's worth, I find the two photos you posted to be very close and I wonder what they would look like printed out on A4? Just a thought...

 

sean

[sean_mclennan]

To be completely absurd, I pixel peeped both inmages at 1200%, and the difference between the Tamron and the Canon is definitely there, but what I find odd, is the clarity difference has a spotty pattern to it. It is not an even or linear difference, rather, there are spots of low detail contained within the image...especially in the corners. As both lenses picked up the print screen pattern, there is a basis for comparison. In this pattern reproduction, I see spots of softness on the Tamron.

 

This pattern/spots makes me think your lens is not clean. You said you purchased it used, have you completely inspected/cleaned all of the elements? Other than these spots seen at extreme magnification, the clarity/sharpness if pretty darn close if you ask me, but I would still give the nod to the Canon. (of course a prime SHOULD perform better than a zoom...)

 

sean<div></div>

[pablo_s]

Thanks for the replies! The shots were taken with a Canon 10D, highest quality jpg, ISO 100. No postprocessing at all (except cropping and saving as a 80% quality jpg). The focus was at about two feet, so I guess that explains the difference in focal length.

 

And Sean you're right, the difference is unlikely to be visible in real-life shots. I'm actually quite impressed by the performance of the Tamron given the price.

[pablo_s]

Sean, wow, that extreme pixel peeping is interesting.

 

First of all, if one has to magnify to 1200% to find a problem with a lens, then that has to mean the lens is actually pretty good! :)

 

As for the reason for these soft little areas, I'm not really sure. Superficially, the glass elements seem quite clean. Some exterior dust particles are always floating on the external part of the front element, but AFAIK they shouldn't appear in the picture (and by the way my Canon 50/1.8 does have a few specs on the front lens). I checked and I also had a couple of dust particles on the back element. I will clean it and repeat the shot to see if I notice any difference...

[kipling]

If you're going to be using this camera to take pics of microscopic type on hamburger

packages so you can read them later then you're better off with the primes.

Otherwise...STOP taking pics of microscopic type on hamburger packages.

[ron c sunshine coast,qld,a]

Why compare them at f5.6? ?

<br>Everyone knows all lenses tend to be close to equal when stopped down

<P>Test them at f2.8 before even considering anything else

<p>