Back focussing issues on a 17-50 Tamron
I only ask because in my experience, the 'central point' is actually more of a small region than a point, so the camera may be focussing on a point further back on the boat. It looks to me like the twig on the right hand side is in focus on the AF version, which might have been near enough to the 'central point' that the camera is focussing on that (as it may have higher contrast than the tip of the boat).
I have been frustrated by similar results in the past and eventually put it down to the AF not always focussing where I thought it should and can usually spot when this happens in the viewfinder and re-AF if necessary.
Do other AF lenses you have do similar things? It's worth bearing in mind that AF inaccuracy is highlighted by wide aperture lenses such as the 17-50. If not, +1 for send it back and get another one.
Apologies if it's a stupid question, but presumably in the example above you are certain the AF point was on the tip of the boat?
Good remark. AF is not the God and you still have to get used to it and make sure it focuses correctly or simply - where you plan. I have a good example - my AF miss rate is low, as I am constantly monitoring how the AF is locked and my eyesight is good enough to tell that if it is not correct. Then for my girlfriend who just "clicks" the button, of course the miss rate is much higher.
Do simple test. Take a newspaper, book etc... open a page and focus on the certain part of the text and make sure it is in focus in Viewfinder. Then check the picture - if you see the same, lens is ok and it is you who needs the "exchange" , if you see misfocuss in picture - that means the lens has focuss issues.
Fan of DA limited and old manual lenses
I've been following a thread elsewhere which majors on this issue, but, to ensure it's a lens problem try shooting a subject using the Tamron plus another lens at the same focal length, aperture, etc.
I'd take the test shots with the camera mounted on a tripod using a static target, being very careful not to move the camera body between shots and ensuring that the AF focus point is on the exact same area of the target.
Welcome to the Tamron 17-50. I don't believe you will find a copy that won't do this. I recommend checking focus on the screen immediately after the shot. I have my K200D set up to zoom in 8x with one click of the rear wheel for checking focus quickly.
I used to own Tam 17-50, that did not have these problems. I am more of convinced that most of the complaint cases on back/front focusing is caused by users & camera AF interaction. In the end, AF is an automated solution that focuses on something by certain rules and, as we all know, this can never be 100% accurate and sometimes, especially in low light or high-contrast cases, it is fooled often enough
Welcome to the Tamron 17-50.
I sent back two copies of this lens a couple of years ago with the same problem.
A friend of mine had a good copy which I borrowed and which was a different experience altogether, so I suppose it depends on luck (and your camera - no individual lens focus adjust on the K-x meant it was a pain).
The second copy, I only had an hour before I needed to leave for the aiport and had to make a decision quickly over whether to take it or not. I'm glad I made the decision to keep the lens as 95% of the shots are fantastic, especially the ability to use f/2.8 throughout the focal length. However, it is annoying that the lens does not consistently focus as expected, hence one can never really trust it, and then you end up having to check each shot after taking, as suggested above. I had occasions whereby I'd take 4/5 shots of the same thing and only 1 would turn out ok... I'm not sure about the AF drifting when the kit lens appears fine for me (although to be fair, I did not take that to Sri Lanka with me so I never could test it in exactly the same conditions at the time).
Mike: I am interested in this hacked firmware, any tips or more info??
Anyways, Amazon will take the lens back, who I must say have been great to deal with. They won't however send me another one, apparently they only ever send one replacement. So I get a refund and then have to re-buy another copy from them. Bit of a faff. Worth it to get a good one (hopefully) IMO, as from the few shots that I've so far processed, this lens can be incredibly sharp.
Matt.
Pentax 17-70 f4 at Amazon £302.92 http://www.amazon.co.uk/exec/obidos/ASIN/B001F514EA/watersphotogr-21/ref=nosim
Worth it to get a good one (hopefully) IMO, as from the few shots that I've so far processed, this lens can be incredibly sharp
+1
It's definitely worth persevering, as it's a great lens. I was lucky, it seems, in getting a good copy first time and any focussing issues I've had generally result from user error!
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58 posts
12 years
Munich
I recently bought a Tamron 17-50 f/2.8 for my k10d from Amazon. The first one I received had pretty bad back focusing issues. I contacted Amazon and they sent me another straight away. Unfortunately I was off to Sri Lanka, for which I needed the lens, and only had an hour or 2 to test the replacement. It performed a lot better, so I took it with me.
I've now returned from holiday, and whilst most shots are as expected (very sharp this lens!), there are still some shots where the focusing is all over the shop. I realised this at the time on one occasion and did one AF and then MF. See below for example shots. Both taken same settings, single centre focus point. This happened fairly regularly, although sometimes the AF would turn out great, the next not so great. Weird.
Now my question is, do I send this one back too? I'm fairly new to buying lenses. Is this something one has to put up with? I have to say that I'm 90% happy with the lens, it is annoying however to have to take multiple shots of things in case the focusing is off. I'm still (just) within the 30 day exchange policy with Amazon so I could try another copy. What are peoples thoughts?
Here's the full AF:
And now the MF:
Now the crops. AF:
MF:
Thanks for any advice, Matt.