soft images on 350D and 17-85 IS USM

[Poolstok]

Hi all.

Apologies if I missed this thread somewhere in the archives. If I did, feel free to throw a rotten tomato at me. Just attach the link - ok?

I only recently learnt that a camera's sensor could also be adjusted for better focus. This comes as a surprise as I would guess that the sensor is at a fixed distance from the lens at all times. Or maybe they do it by another means. Who knows.

Anyway. My problem is that i continuously get softer than desirable results. I just had both my 350D's serviced lately, so to re-service them again so soon is a tad costly - but if it will definitely help - then so be it.

Is the 350D inherently soft? Am I focus - recomposing the wrong way? Am I not steady enough? Do I need a faster lens (17-85 = 3.5-5.6 if I am not mistaken)? Should I give up completely?

I just find waaaay too many images that are not focussed on the face, but on the chest or somehwere in the B/G.

URGH!

BTW, I am getting a 40D as soon as the public opinion gives the green flag - will that help?

Feels funny for a semi pro to ask such a 'silly' question!

Thanx

Pools

[Geurt]

"Pools" the lens you are quoting is not very well know for its sharpness, sorry for being the barer of bad news.
Check camera by getting your dirty paws on a prime lens and see if they are well "tuned" aka back or front focus issue. If that checks out ok, then I'd guess a very good check with lens and finding its sweet spot. Consider delaying the 40D purchase and go for something like the 24-105 F4 L lens as it has a very solid following on its capabilities and sharpness. If pin sharpness is the required reference, then mate revert to primes such as 35mm, 50mm, 85mm and 135mm Canon lenses who all have excellent trek records.

[camu]

Consider delaying the 40D purchase and go for something like the 24-105 F4 L lens as it has a very solid following on its capabilities and sharpness.

My mother used the 350d and when using my 24-105 F4 L lens had stunning results. Super sharp and on spot every time practically. Not having a 350d myself and only using hers occassionally I can't say too much about it, but what I can tell you is that using the L lens mentioned above produced exceptional results. When using the Canon 90-300 the results were great but not close to the L lens naturally. No focussing problems at all.

Good luck with this....... sounds like it could turn out to be an interesting thread.

[Poolstok]

Ai-yay-yAi oom Guert....

Well, with the 40D I wanted to get another 17-85 and maybe the 70-300 IS USM "hidden L" or 70-200L 4.5.

I thought that the 17-85 is fairly good. At that price at least - well, it's not an L but still....

Ja. I think you are right. Get a decent glass and re-do all the focus tests. WOuld you reccommend tha 45 degree ruler shoot method for the test?

What lens would you recommend?

Depressed Pool

[Poolstok]

Thanx Camu...

This can REALLY make one doubt your own abilities!

[camu]

As a matter of interest pools - how do you recompose your shots? Perhaps that has something to do with it, and stupid question this but where is your focal point set? I ask this 'cause a friend of mine had a similar problem and when I used her 20d to check it out for her found that she had the focal point set to the centred point only, hence the chest was in focus and the face etc slightly soft. Hope that makes sense

[Poolstok]

I used to do it like that as well, but then read the article about that. I now place it to the nearers FP to the face. Could it be that I do not 'follow through' - move the camera too cuickly - not enough to see motion blur per se - but enough to get a 'soft' image?

I never use the A-Dep function - but I am considering it now - at least I will know what is in focus!

[donald007]

Poolstock,

I have been trying to understand the issue of back focus and front focus for some time now. It appears that the theory says that the autofocus system of the camera should be accurate to one third of the DOF of the lens at full aperture. Testing my 400D with effectively a 280 mm f4 at a range of about 3m this means that it should be accurate to about 7mm. Mine seems to consistently be focusing about 14 mm in front of the target at this range and on my sons 350D with a quick comparison it seemed to be more like 30-35 mm in front. Since the DOF at F4 is only 20 mm the image will obviously be soft and you need to increase the f stop to get an in focus image or compensate by focusing on something slightly further back. I have read somewhere that as soon as the focus motor brings error within range the camera accepts that it is now in focus so it may depend on whether you are initially focused behind or in front of the object that you are now trying to focus on as to whether it backfocusses or front focusses. So far I have not proved this , mine seem to front focus most of the time. I have used 2 different focus charts to test this with little difference between the 2. Let me know if you want info about the 2 charts and I will see if I can dig them out for you. So much for understanding it and hence working around the problem. Fixing it ? Haven’t really dug into that aspect yet.

Bruce

[Poolstok]

Hmmm.... so wahat you are saying is that if I have focussed at 10m previously, and now have to focus on 2m, it is better to focus on the tip of the nose so if the motor 'stops'. the focus plane would hopefully be on the ears - or somehwre like that) and vice versa - focussing on the ears and hope to get the nose if your previous focus was closer than the present one?

Here is another thing I do which may shed some light. I have grown into the habit to focus on hard edges - like the side of somebody's head. This gives more contrast with the B/G. could it be that this is the problem? The side of the head is after all about 8cm from the eyes. And then maybe sometimes in the rush I do not notice that maybe the camera focus on the background (when the background is relatively close to the face) and therefore I stuff it up myself??...hmmmm.....

I wish I could get that 'split prism focus plane' bask in my camera - good old manual focus!

[Geurt]

.....
Ja. I think you are right. Get a decent glass and re-do all the focus tests. WOuld you reccommend tha 45 degree ruler shoot method for the test?....

Download this article, study it and use the included printable target to do tests.

Get best tools for your task aka best lenses first, then get better bodies.

Check the secondhand market Johan, there are frequently excellent stuff on offer. I think Darrel had a 70-200f4 very well priced, there was a 24-105 f4 IS offered at a good price recently as well. Yeah and I know, those things cost money, but you are doing work at pay frequently and as you'd know you cannot afford it to redo stuff due to soft lenses or not sharp enough images.

[jab2]

It must be remembered that a mis-adjusted sensor will not give an overall soft shot, but merely a shift in focus. On some subjects it is however difficult to see if the focus is in the wrong plane as you might just have air there and you would perceive a front/back focus problem as soft all over. The angled ruler trick is still the best non-technical way of checking whether the sensor and the autofocus sensors are in agreement to the same focal plane.

[Poolstok]

Maybe 'soft'is a bit soft a term. Sometimes the fases are just out of focus - not radically so - but more than 'soft'.

Thanx Geurt - that is the test I have. Good article!

I al looking at buying more decent glass when I get the 40D. Just that I'll be using the 200 or 300 at weddings to do candid hunting for my wife - so the IS is a must. as for 2.8...... shees mate!

But I'll be poking around about the glass when I get there.

So, in effect can we say that with the setup at the moment, i could expect less than ideal results? Is it worh getting the body's focus checked? I suppose I should eh?

[Pine]

Poolstok,

I am using a 17-85 and although it is not as sharp as my 85 1.8 I would not say that I am disappointed with the sharpness of the lens, given that it is a non L with quite a long zoom range. I know the lens is softer wide open so I stop down to f7.1 most of the time.

For portrait work selecting the point of focus is very important, I always try to focus on the corner of the eye (next to the nose) of the eye closest to the camera and allow for enough DOF to cover the nose and other eye. The corner of the eye provides enough contrast for focusing.

I actually found using the 85 1.8 tends to exaggerate focusing errors as larger aperture setting and is therefore less forgiving than the 17-85.

[squirrel]

Don't know how soft your idea of 'soft' is, but this is a 100% crop, unsharpened, from my 27-85 wide open on my 350D...

And some 350D/EF-S 17-85 images in my gallery:
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874
http://www.outdoorphoto.co.za/forum/...00&ppuser=3874

Not L glass, I agree, but not exactly soft either. If yours is significantly worse than these, I would get my body and/or lense checked.