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


brian1208 18 11.8k 12 United Kingdom
20 May 2010 2:53PM
Another thought that may help us to help you.

Set up your lens on the tripod and set your camera to on-shot focus, all points activated.

Focus on a local TV aerial on a nearby chimney mast (not a satellite dish but the old fashioned kind with vertical and horizontal bars.

Set the lens to the widest aperture and leave ISO at 100.

Use cable trigger or timer shutter relase.

Shoot at 200, 300, 400, 450 and 500mm, first pre-fcoussing with the AF off, then switch on AF and get the shot
then without pre-focus do the same again. (note and record the aperture showing at each focal length)

This will show several key points:

if there is a general problem with the lens on your 40D none of the shots will be in focus

if the AF only fails once the aperture reaches f6.3 then you have identified that your lens / camera combo cannot handle this situation

(I suspect that you will find that you get good focus lock at all focal lengths in this way as this was my basic test routine for my tamron 200 - 500 when I thought I had focus problems. The vertical and horizontal lines appear to work best with the AF sensor)

Obviously this test is best done in good light although with mine I get good focus lock even in grey overcast with this test (my aerial target is about 20 yds away)
brian1208 18 11.8k 12 United Kingdom
20 May 2010 3:28PM
An example of what I mean, shot 10 minutes ago in grey overcast light, 500mm with f6.3, all AF points active (its off-centre because I have to shoot around a large shrub that has now filled in with the onset of spring!)

The second image is a crop of where the focus point selected as in focus and post processed to lightned it a bit to show more detail + USM applied to show what is there.

Instant lock on without pre-focus (ie: no hunting)

aerial-test-shot-1.jpg


aerial-test-shot-crop.jpg


If I'd focused on the LCD panel you can just about read the text, as it is its picked a spot just behind and you can read the "X" manfr's label on the rear upright
lawbert 14 1.8k 15 England
20 May 2010 4:02PM
Ive just had a quick look at your portfolio Sandra and you certainly are well aware of when something is focused sharply and not Grin (contrary to what WE says)
I had a sigma 50-500 which was an f6.3 at the 500 end to be honest it was pathetic at 500mm even stopped down to f10 (which still bought out unsharp images).....It was only achieving sharp focus at 420mm at f8 but the best sharpness was at 200mm at f 7.1
The superzooms seem like an attractive buy but they really try to do to much and achieve very little unless you are prepared to spend hours working out at what focal length and aperture the sharpness comes from.
If I was you I would sell it on ebay and get a 300mm f4 and a 1.4x convertor or take a gamble on a good copy of a sigma 120-300 f2.8 with a 1.4x convertor which will give you what the extra focal length your after and sharp images as wellGrin
brian1208 18 11.8k 12 United Kingdom
20 May 2010 6:46PM
I've added another image to my PF as part of this story.

This one was shot indoors at about 3mtrs distance in very low light (shooting info is on the upload). The key finding is that so long as the focus point (single point focus this time) was spot on the green to red border of the tulip petal there was instant lock-on with no hunting. Shifting the focus point one notch off the edge in any direction resulted in loss of focus lock and continuous hunting.

My conclusion, shooting at this focal length and aperture with the razor thin DOF requires spot on focus point location, near enough just won't do (but then I guess its the same with any long focal length lens, I haven't experience of any other long stuff apart from the sigma 150 - 500, which seemed just as finicky when I tried it on my buddy's Nikon)
kenp 15 96 United Kingdom
20 May 2010 7:33PM
After reading this I have come to the conclusion that Warehouse Express are "Rogues!".......For the sake of customer services alone,after the amount of equipment you have purchased from them,they should have replaced the lens straight away!....they seem to be fine as long as everything is working fine,but give them a problem and they don't want to know!. I take it Sandra you will be no longer using "WE"............................................Ken
Blenkinsopp 15 320 4 England
20 May 2010 9:24PM
Hi folks,
Thanks for all your support and suggestions but to be honest I just want to get rid of the lens - when they eventually send it back to me


This is a copy of the email I received this morning - Convenient that there is no mention of the numerous phone calls I made - starting the first week in February. I can't prove I was fobbed off for all that time - I give up!



Quote:Dear Sandra Myers,



I have been forwarded your email by Melvin, regarding your Tamron lens.



You first received your lens in February 2009 and reported it faulty in April 2009. We sent this away for testing and it came back to us as ‘no fault found’. Eleven months later you reported the same fault and once again the experienced technicians at Intro 2020 have not been able to establish any fault with your lens after extensive testing.



As a retailer our responsibility is to ensure that the goods conform to contract at the time of sale. As no fault has been found on the two occasions that you have reported, we would have to assume that an inherent fault was not present at the time of sale and therefore this contract has been fulfilled.



In all cases, the consumer must be able to prove that the fault or failure to conform to contract existed at the time the goods were purchased. If you are unable to do so, then there is no legal redress against the retailer and they are under no obligation to offer compensation.



Melvin has instructed Intro 2020 to continue testing into next week but if still no fault is found, your unit will be returned to you straight from Intro 2020.



If no fault has been found on these two occasions, proof that a failure is present and is due to an inherent fault at time of purchase would need to be verified by an independent qualified engineer. Unfortunately, if this is not possible, there would be no grounds to seek compensation from Warehouse Express.



I appreciate that this is not the response you were hoping for, but I trust I have given you a clear explanation of the reasons why we will not be able to assist in the way you had hoped on this occasion.




TAPE ALL YOUR PHONE CALLS IF YOU DON'T WANT TO BE CAUGHT OUT LIKE I WAS!

I won't be looking in on this forum again as it just upsets me that I was so gullible and stupid.

Thanks again folks
Sandra
geoffash26 17 2.5k United Kingdom
20 May 2010 11:59PM
Ive never had a problem with WE service, they've even sent out a replacement item before I returned the faulty one as I was away on holiday in 2 days.

My thoughts are support your local camera shop they will normally have a relation ship with the reps and can normally sort this kind of problem out.... I know mine would and although they may be a little more expensive than buying on the www I know I can 1 test an item before I buy and have the knowledge that if I have a problem it will get sorted

Just my 2 pence
strawman 17 22.2k 16 United Kingdom
21 May 2010 12:14AM
I too buy from a local camera dealer and have benefited from them stepping in.
CaptivePhotons 18 1.7k 2 England
21 May 2010 8:02AM

Quote:I had a sigma 50-500 which was an f6.3 at the 500 end to be honest it was pathetic at 500mm even stopped down to f10 (which still bought out unsharp images).....It was only achieving sharp focus at 420mm at f8 but the best sharpness was at 200mm at f 7.1
The superzooms seem like an attractive buy but they really try to do to much and achieve very little unless you are prepared to spend hours working out at what focal length and aperture the sharpness comes from.



I do not think the Tamron is in the 'superzoom' range, it is more like a very long telephoto. The Sigma 50-500 is a 10x zoom, the Tamron 200-500 is only 2.5x

I used to have the Tamron and whilst it was certainly not the best in the world, I had no complaints given the price and my expectations of its performance.
brian1208 18 11.8k 12 United Kingdom
21 May 2010 8:53AM
I agree with thatbloke (what a lovely phrase Smile ) about the Tamron 200-500.

Its a lens that requires a fair effort to learn how to get the best from it (very different and much harder than the canon 400 f5.6 L for example). BUT with good technique and good light it can produce better images than taking the results from the canon 300 F4L + 1.4 TC and upscaling to the same effective focal length. (in bad light - forget it, the results will not be good in my experience)

That said - it will never match a 500mm prime lens, but it does cost several thousand pounds less - you do get what you pay for in this world!
LenShepherd 13 4.4k United Kingdom
21 May 2010 10:06PM
Trying to take some of the heat out of the situation WE are implying they sent the lens back promptly after the first investigation - presumably April 2009 and there was an 11 month period before you sent it back a second time - implying March 2010.
Is this broadly accurate?
If yes there are obvious problems because of the 10-11 month period.
The lens importers have twice found no fault - which implies they are satisfied it performs to their specification.
The only hope of going forward is to establish if WE implied the lens can do more than the lens manufacturers specification.
If they did the issue is solely between you and WE - and the lens importers specification is irrelevant.
If WE said it does Y and it only does X then it is WE's advice and not the lens that is at fault - for claiming it was fit for a purpose it cannot do.
As it seems other can get their version of the lens to AF on the same type of Canon body as you use the implication is it should AF on your body, and is "fit for purpose".
When the lens comes back try it on another body. If it works on another body it could be your camera body that is at fault.

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