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Tamron 52B SP 90mm f/2.5 Macro -- Woot!
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PostPosted: Fri Oct 16, 2009 2:37 am    Post subject: Tamron 52B SP 90mm f/2.5 Macro -- Woot! Reply with quote
So I got this Tamron 90/2.5 along with a bunch of Canon FD and EOS stuff that my mother no longer uses, and I've had it sitting in the camera bag ever since. Well, today, I decided it was time to exercise this lens some. Mounted it to my EOS XS (1000D) and set ISO to 100.

It was late in the day, so I had to use the camera's flash for hand held photography. The flash worked fine in terms of exposure, but the colors are not very close to reality. Oh well, I was mostly interested in evaluating the sharpness of this lens anyway.

I was very pleased with the results. I did some pre- and post-processing of the images, mostly sharpness and brightness levels in pre-, and saturation and "curves" in post. The settings I used for both the following photos were f/8, 1/60 second, fill flash, ISO 100. The only sharpening I did was in Canon's DPP software, and it was applied to the raw .CR2 files. I find this works much better than applying sharpness routines during PP because it keeps the noise and other artifacts down.



And a 100% crop of the above:




100% crop of above:


This is an amazing lens. I used to own one years ago, but I had forgotten just how good it was. I'm stoked. Can't wait to find some little wiggly crawly critters so's I can take close-ups of them.

Last edited by cooltouch on Sat Oct 17, 2009 6:19 pm; edited 1 time in total


PostPosted: Fri Oct 16, 2009 4:25 am    Post subject: Reply with quote
These samples will help maintain the already formidable reputation of this great lens



patrickh


PostPosted: Fri Oct 16, 2009 5:57 am    Post subject: Reply with quote
I agree, it's always had a great reputation, and for obvious reasons. More recently however, I have read of instances where people who mounted this lens onto their DSLRs were getting large dark spots in the middle of the image area, and it was theorized that this was because of the angle of the receptors on the image sensor and the shape of the rear element, or some such. I don't remember all the details now. But this caused me to want to test the lens and see if I would have this problem. So far, I've shot maybe 50 images with this lens and my XS (1000D) DSLR at all aperture settings and I have seen no evidence of this alleged image defect.

So, while I won't go so far as to say that the lens is getting a bad rap because of this, perhaps it is more fair to say that this "problem" has been overblown.


PostPosted: Fri Oct 16, 2009 7:23 am    Post subject: Reply with quote
Yes, this lens does produce a spot. There's actually a bright spot when you stop it down below about F11. Has to have a fairly strong light in the frame. It's caused by the light reflection off the sensor, then off the flat rear element, then back onto the sensor:

F11 faint circle visible


F16


F32


If you are aware of when this happens, you can avoid the problem. It's certainly a very nice lens otherwise.


PostPosted: Sat Oct 17, 2009 7:36 am    Post subject: Reply with quote
That spot issue is indeed a very strange occurance! Never seen anything like it. Does it happen with this lens on all DSLR's (I shoot Nikon)? I always keep my eye out for one of these tamron 90mm's but I'm not so sure I would like to deal with that spot.


PostPosted: Sat Oct 17, 2009 8:05 am    Post subject: Reply with quote
I have this lens and have never seen the spot. I do always use a lenshood so maybe this stops the problem.


PostPosted: Sat Oct 17, 2009 9:04 am    Post subject: Reply with quote
Ever checked rear lens element - or even inside the lens set?

At first sight, I'd say it looks like a lens flare, but I am unsure.


PostPosted: Sat Oct 17, 2009 9:06 am    Post subject: Reply with quote
martinsmith99 wrote:
I have this lens and have never seen the spot. I do always use a lenshood so maybe this stops the problem.

Nope Sad I use it with a (long) hood and the spot is still there ... I even tried to add a rear baffle but it didn't solve the problem.


PostPosted: Sat Oct 17, 2009 11:53 am    Post subject: Reply with quote
It has to with the fact that the rear element is perfectly flat. If the rear element is convex, the return reflection will be more spread. e.g. the F32 "dot" would look more like the F11 dot, while the F11 dot would be so large and dispersed that you wouldn't notice it at all.


PostPosted: Sat Oct 17, 2009 11:57 am    Post subject: Reply with quote
martinsmith99 wrote:
I have this lens and have never seen the spot. I do always use a lenshood so maybe this stops the problem.


It' not extra light entering from an angle causing the flare, it's purely the reflection off the sensor(of the aperture) -> flat rear element -> onto the sensor again.

That shot I posted, I deliberately made it a back lit shot to enhance the effect. It has to be a combination of a bright background and a darker area in the MIDDLE of the frame to see the spot.

If the main object is bright compared to the background and in the center, then you probably won't see any spot.


PostPosted: Sat Oct 17, 2009 2:19 pm    Post subject: Reply with quote
It's a problem that never, as far as I know, raised its head on film cameras, due to the extra shininess of digital sensors. The solution is to take some emery paper to your sensor Twisted Evil


PostPosted: Sat Oct 17, 2009 3:09 pm    Post subject: Reply with quote
A less permanent solution is to put some thin tissue paper in front of the sensor... this eliminates nearly all the image defects Twisted Evil
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