Tamron 28-75 - how to test?

JJ!

JJ!

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So I have on loan a 28-75 Tamron. I know that this lens has good and bad copies but how do you test for focussing issues and sharpness. I'm pretty uselss as the tech side lol. Before dropping £££ on the VC version I thought this was worth looking at first.

I don't want to commit to this copy if its no good.

Below are my initial test shots at 100% crop but slightly resized.

Difficult test subject, maybe should have used something bigger?!

What does everyone think? Any better suggestions on how to test and how to check for front/back focus?

Test1_zpsejngnlck.jpg


Test5_zpshwfi6wes.jpg


Test2_zpsgylfskot.jpg


Was focussing on the eyes, but it looks like the hair might have been caught in focus. The focus point was only just smaller than the head!

Test3_zps0lzzrpnp.jpg


Test4_zpsgqcjqjy6.jpg
 
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They don't look too far off from my experience of the lens which is that it is a little soft wide open but otherwise very sharp.

Difficult to tell if it is front or back focussing as as there is no depth to the target, Google will show you many ways to do this.
 
Thank you. Found a couple of things on google to test for front/back focussing so will give that a go.

I'm not sure what kind of results f2.8 should be giving, or if the VC version will produce sharper images. Obviouslt my test subject was on the rather small side and might do some more life size image testing.
 
You need to test it on someones eye, preferably at iso 100 with a good shutter speed. IMO.

F4 obviously looks better as you would expect... I'm on my phone at the moment but will have a look tonight.

Have they had any sharpening at all? D750 files sharpen up really well from my experience so apply sharpening as you normally would.

Tamrons VC is excellent. Really really good and it will also offer you an extra 4mm if you went with the newer model. It'll probably have better coatings too and will probably be nicer made. 'Probably'
 
No sharpening - just straight out the camera and cropped. Its hard to compare it against anything else as its currently the only zoom I have. Will find a better subject and try again tonight or tomorrow. In the mean time I might accidently order the VC version to compare. Only downside is that the VC version stops me buying any other lenes for the time being!
 
Nice addition! I either get the Tamron 70-300 to go with the 28-75 or get the 24-70 VC. The 28-75 is a great size and weight, but if its not sharp enough, its just not sharp enough!

Weill go find someones eye to test lol
 
You really have to test with something bigger, in order to check if focus is accurate.
Maybe with some batteries, like this. It's a simple test that will certainly help you. Do it with a tripod.

Regarding sharpness, it may be that the lens is sharper at f4 (that would be perfectly normal), but it also may be that using f4 eliminates some focus error, due to having a bigger dof.

Test it and let us know.
 
Thanks! Will try the battery test later and see how it performs. And post results.
 
My advice don't 'test' it use it! Go out shoot what you normally would how you normally would and asses the results only if they disappoint you start to dig deeper this approach can save you a world of pain and hurt.
 
I've used a few of the Tamron 28-75 and I agree that the performance above at 2.8 is consistent with my own experience. Basically it's pretty soft at 2.8, sometimes barely usable. f/4 and above it's a great performer.

Overall when you factor in the price it's a great lens for the money but outclassed by the newer Tamron 24-70 and of course the Nikon mid range zooms. The 2.8 on the 28-75 comes in handy for those OMG moments but it's not something I'd use it at if I can help it.
 
a1ex2001 said:
My advice don't 'test' it use it! Go out shoot what you normally would how you normally would and asses the results only if they disappoint you start to dig deeper this approach can save you a world of pain and hurt.
Click to expand...

Very true! My time with this lens is limited though so I best start! I need to give it back or buy it!
 
AF points - never thoight about live view - not sure why!
 
And don't forget that when conducting this level of pixel peeping that everything else has to be spot-on too!
That includes base ISO, tripod, cable release, mirror lock up (or live view) and don't let anyone walk around near you when you take it :)
 
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