Can't get really sharp images on EOS 40D

[icassell]

Garbz,

I think one can compare the Tamron 17-50 to an L lens. I did compare them side-side when I bought it. I had the option of buying either and I love that Tamron (which is not particularly cheap, just less expensive than Canon). The build is good and the optics are excellent ... I just miss USM (which hasn't been a real issue for me).

 

[MDesigner]

I can be objective if I want to. I'll do so now.

reg had some good advice when he said "BTW quit staring at 1:1 crops. You'll drive yourself crazy." The other comment, "Is a prime lens a lens?" was a snotty way of saying "yes, the rules applies to prime lenses." Maybe reg is a photo god and finds my questions silly. If that's the case, maybe he should keep in mind this is a beginner's forum, and maybe he's better off spending his precious time with pros than trying (key word there) to help photo newbs. If he continues to hang around the beginners' forum and make snotty comments, I'd start to wonder if maybe he just gets off on talking down to people he regards as not as skilled as he. I'm a photo newb, but I'm a pro in another trade, and I NEVER talk to newbs like that, ever. Why? Because I'm not a jackass.

There. Oh I guess that last part there was a little subjective.. sorry. :roll:

 

[elemental]

Might I be the only one who's thinking that at most one (and possibly neither) of the crops are areas that are in focus, seeing as how they appear to be different distances from the camera? Maybe I'm missing something or pointing out the obvious, but I would imagine a lens wouldn't be very sharp away from its focal point (particularly at f/2.8).


It would be great if this thread actually survived on topic instead of turning into another Beginners' Place bickerfests (yes, that apostrophe drives me crazy).

 

[Chris of Arabia]

Might I be the only one who's thinking that at most one (and possibly neither) of the crops are areas that are in focus, seeing as how they appear to be different distances from the camera? Maybe I'm missing something or pointing out the obvious, but I would imagine a lens wouldn't be very sharp away from its focal point (particularly at f/2.8).

That looks to be a fair point, though given the size of the image as presented, I'm struggling to work out where the point of focus actually is in this shot - my guess is that it's nearer the camera than either of the two 100% crops.

 

[Mav]

Might I be the only one who's thinking that at most one (and possibly neither) of the crops are areas that are in focus, seeing as how they appear to be different distances from the camera? Maybe I'm missing something or pointing out the obvious, but I would imagine a lens wouldn't be very sharp away from its focal point (particularly at f/2.8).

Yeah that's what I pointed out above. Technically only one of those crop areas would be in perfect focus, assuming the camera actually focused on one of them. At 17mm and f/2.8 the depth of field should be quite large which is why they looked about the same. Still, at ISO 800 you're looking more at the camera's high ISO capability than anything else. It'd be easier to see at ISO 100.

 

[terri]

Stay on track and play nice, all. There is good information here.

Thanks.

 

[MDesigner]

Point of focus was infinity, I believe. I was focusing about where the truck is.

And BoblyBill: Thanks for the welcome. I'll definitely be posting photos as soon as I come up with some decent ones I feel are worthy of sharing.

Actually, I do have something I shot years ago, with a Nikon Coolpix 8700, and stupidly lost the original unprocessed JPEG. Quite sad about it.. as now the shot only exists in 640x480.

 

[MDesigner]

OK, so I got home and set up my tripod, and forced ISO to 100, zoomed to 50mm, put the 40D in Av, and tried two different shots using the 2-sec timer. Focal point was the barcode. (these crops are 1:1)

First one is f/4.

Second one is f/5.6.

Wow, what a difference. Dao's advice on f/4 at 17mm and f/5.6+ at 24-50mm was spot on.

This brings up some questions. Does this mean at 50mm, f/4 will never yield sharp results on this particular lens? I imagine f/2.8 would've been even worse.. and even at 17mm, f/2.8 might've looked crummy. So why would we want to sink the cash into a fast lens (I realize f/2.8 isn't amazingly fast) if the widest aperture yields blurry results??

 

[BoblyBill]

Hmm... I have a hard time believing that there would that much difference between f/4 and f/5.6 actually. Were you shooting on manual focus or auto? I would think that the f/4 shot didn't get the focus right.

 

[BoblyBill]

By the way... I like the diamond picture... that's cool.

 

[MDesigner]

You're right. Here I was trusting the Tamron's AF too much.. bleh.

Auto-focus:

Manual focus (using the very kickass Live View feature):

That's not cool. So it seems maybe the Tamron's AF is a bit off at f/2.8?

 

[Mav]

The focus may very well be off, but if it's off it'll be off regardless of aperture. You'll notice it more at larger apertures like f/2.8 because your depth of field is smaller there (less in focus) so mis-focusing is easier to see.

 

[MDesigner]

Ahh, that makes sense.

I think this is the focusing problem many people have claimed this lens has. Some people have returned the lens and gotten the exact same model in exchange and that one winds up working better. It might just be an issue of the lens needing to be calibrated (someone else's words, not mine).

I'll have to do some more AF vs MF tests and see if it's consistently off. I've never noticed it till now. I'm glad I did these 1:1 comparisons, otherwise I would've never noticed this issue.

 

[Mav]

I'd try a test chart like this to confirm it: http://focustestchart.com/chart.html

 

[Dao]

Ahh, that makes sense.

I think this is the focusing problem many people have claimed this lens has. Some people have returned the lens and gotten the exact same model in exchange and that one winds up working better. It might just be an issue of the lens needing to be calibrated (someone else's words, not mine).

I'll have to do some more AF vs MF tests and see if it's consistently off. I've never noticed it till now. I'm glad I did these 1:1 comparisons, otherwise I would've never noticed this issue.

Just wondering, is your lens assembled in China or made in Japan?