What lenses do you expect to auto focus on your camera?


Blenkinsopp 15 320 4 England
18 May 2010 4:39PM
I bought a Tamron 200 Ė 500 f5.6 Ė f6.3 lens and the autofocus searched continually and didnít lock on. (the lens was on a tripod and I tested it on high contrast static objects in good light e.g. plant food packets and paint tins with black and white writing standing on a wall.)

After returning it twice (it has been away more than 6 weeks this time and Intro 2020 have failed to get back to Warehouse Express about it) I have been told by a Warehouse Express person that I wonít have any come back about the auto focus as both Canon and Nikon only say their cameras auto focus with lenses of f5.6 or faster

What would you do in my situation?

I know of loads of people using auto focus with lenses that are f6.3 at the long end - was I naÔve in expecting auto focus to work?

Iím gutted if I have wasted all that money and feel cheated that there wasnít a clear mention of this in either the lens or camera information.

any advice please,
Sandra
brian1208 18 11.8k 12 United Kingdom
18 May 2010 4:49PM
Sandra, what camera are you using the lens on?

I have one and use it on my canon 7D and have no problems focusing at 500mm. Yes, it will hunt if it doesn't lock first time but it always picks up the shot and returns a good image most of the time. With good contrast and no confusion in the background it locks very quickly (good enough for birds in flight etc).

I find that using the multiple focus points works best for the flight shots in clear sky and single point works best when the subject is against a confusing background.

(Its also a nice lens to manual focus)

What happens if you use manual focus to start with, get the subject locked on then switch to AF? Also, does it vary depending on subject to camera distance?

Its the first time I've heard of this problem (and I did a lot of searching for this and any other potential problems before I made my purchase)

I've got a few images shot with this lens on my PF and more on my foliopic website

hope you get this sorted

Brian
brian1208 18 11.8k 12 United Kingdom
18 May 2010 4:56PM
I've just put up a new image from a couple of days ago to show what it can do
Blenkinsopp 15 320 4 England
18 May 2010 5:01PM
I use a Canon 40D and decided on this lens after reading that the Sigma 150 - 500 had some compatibility issues with the 40D.
The autofocus hunts every time you half press the shutter button and even on the rare occasion when appearing to lock the image is out of focus.
Blenkinsopp 15 320 4 England
18 May 2010 5:13PM
your image is fine - I wanted some shots of the dippers without getting wet feet (only have a 70 - 300) but can't even get a shot of a plant food packet as sharp as yours with the lens "screwed down on a tripod"

The "lens test" and letter I received from Tamron when the lens was returned the first time annoyed me. They said that I should use a tripod to get sharp shots and their "lens test" image consisted of a street scene which didn't look very sharp to me. (I use a wide angle lens and WALK if I want a street scene!!!!!!!!!!!!!!)
brian1208 18 11.8k 12 United Kingdom
18 May 2010 5:16PM
should work with that Sandra, and, with respect to them, the WH person was talking out of their nether regions!

have a look at the photozone on a 350D and the comments at the bottom of the photodo tests here

Many (all?) of the "Superzoom lenses that have f6.3 at max zoom work on current APS-C cameras (my 7D happily reports f6.3 as the aperture at 500mm)

Its either a faulty lens or (just maybe?) something wrong with your technique - but it should AF on your camera (from the Intro 2020 publicity for the 200-500
Quote:For Canon AF,Minolta AF-D,and Nikon AF-D cameras.

strawman 18 22.2k 16 United Kingdom
18 May 2010 5:32PM
You are into a grey area here. For example the 70-500 used to report itself as f5.6 not ~F6.3 on my 300D in order to tempt the AF into life. As the sensors are analogue parts there will be some variation camera to camera so it is possible that your camera is on the edge of being able to focus it. I know my 300D struggled (same AF sensor type as 350D I think) and the 40D was much more positive with the same lens. On the 300D its performance varied sensor point to point.

Did you try it on the centre point only. That may work best.

So canon will say is it to the AF spec and a Canon lens, well no, so its not their issue. It is possible the lens is fine and it is your camera that is marginal

My view is if they say the lens is OK you can prove it does not work on your camera so you should get your money back. WE are normally good at that sort of thing.
Blenkinsopp 15 320 4 England
18 May 2010 5:32PM

Quote:Its either a faulty lens or (just maybe?) something wrong with your technique


I wondered if it was something I was doing so let a couple of more experienced photographers try it. (Neither got sharp shots and one said it was "rubbish" even for a budget lens) It was after they tried it that I returned it for a second time.
18 May 2010 5:45PM
Doesn't the autofocus on the 40D stop working when lenses have appertures F/5.6 or greater?
Overread 13 4.1k 19 England
18 May 2010 5:50PM
AF on any canon camera body that is not a 1D line will stop if the maximum aperture of the lens goes below f5.6 - so at f5.6 you retain AF, but any setup after that will lose AF.

However - sigma lenses that go to f6.3 will fake their report to the af part of the camera so that whilst its aperture report to the camera is correct, it will still allow af to function without problems. This is similar to when people use 1.4 teleconverters on lenses like the 100-400mm and the 400mm f5.6 and they tape over the reporting pins so that the camera does not "see" the teleconverter and thus retains its AF functionality (albeit with reduced performance as the lightloss itself is still very real).

From my understanding you should still retain your af with the lens you are using, but you are pushing the AF of the camera at f6.3 - so you need good lighting and good contrasty subjects to get a good lock. The af performance of lenses that are nativly f6.3 at the long ends tends to be far superior than most teleconverter based AF setups where the aperture goes smaller than f5.6 (very general statement there).
Blenkinsopp 15 320 4 England
18 May 2010 5:51PM
How do I prove that the lens doesn't work with my camera? Sending an out of focus image could have other reasons for it.

Fiddler - I didn't know that f6.3 lenses shouldn't focus on the 40D and there are images posted with 40D and f6.3 lenses with no mention of manual focus
Overread 13 4.1k 19 England
18 May 2010 5:59PM
If you need to test get something that is stactic and has a high contrast difference over it (AF - as far as I understand it) works partly upon contrast differences within a scene - so a flat monotone subject will be harder to lockonto for the AF) and try it out in good strong lighting. The camera should be able to aquire an AF lock. Also if the lens has limiter switches on it makes use of them to limit how far the lens is to use of its focus. If you are shooting birds long distance you can easily set it to have a few meters of focus not being used because you won't be that close. If you don't have limiter switches you might find that a quick manual focus or prefocusing on something in the scene helps speed up AF locks as it has less to move through.
Blenkinsopp 15 320 4 England
18 May 2010 6:25PM
Alex - I tested as you suggest - see my first post.
Can't try anything at the moment - WHE received my lens on 31st March and sent it on. Intro 2020 haven't returned it to them yet. Intro 2020 promised to get back to them about it last week and haven't. Things are going nowhere at the moment!
kenp 15 96 United Kingdom
18 May 2010 7:54PM
Hi Sandra!.........my advice is to get on to Warehouse express and ask for your money back,the lens is not fit for purpose. They are selling the lens in canon fit so it should work with Canon cameras fullstop!. They are the retailers so they are responsible to the customer,dont take any hassle from them at all,if they wont play ball,contact trading standards!.......When you get your cash back,deal only with SRS!.......ALL THE BEST MY FRIEND.......KEN
f8 18 9.2k 22 England
18 May 2010 8:07PM
SRS don't do Canon!!

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