[jradley]

Hi,

Ever since I got my EF-S 55-250 IS I have been somewhat disappointed with it. I'm not sure if I have a faulty copy (doubtful), if I'm not experienced enough to get the best out of it (possibly) or if it just doesn't meet my expectations (probably).

My main complaint with the lens is chromatic abberation and soft (or possibly incorrect) focus. To show what I'm on about I'll post an example below.

Maybe I'm just being overly fussy ? If this is a case of what I should expect for a £180 zoom then I'm stuck for ideas as to what to get as a replacement. I'm not convinced (from reviews I've read) the EF 70-300IS is significantly better. Are there other alternatives that would give appreciably better results without stretching to L quality and if L really is the way to go, are there any duds to avoid at that sort of length ?

Any thoughts much appreciated.

The example shots:

First up, straight off the camera, no PP just reduced in size for up/downloading. The bird looks rather soft and you can see the CA.

1/640s / f8 / 194mm

[IMGLINK]http://farm4.static.flickr.com/3116/3170576556_b28fd36058.jpg[/IMGLINK]

and a 100% crop to see more clearly....

[IMGLINK]http://farm4.static.flickr.com/3262/3169746771_f019315d9f.jpg[/IMGLINK]

When it gets it right (again 100% crop)....

1/500s / f8 /214mm

[IMGLINK]http://farm4.static.flickr.com/3113/3170576652_a79630200c.jpg[/IMGLINK]

Cheers,

John

[drb5]

Looks to me like the focus is shaprer on area's of the branches rather than the bird and those parts look good.

[bigtim]

Santa brought me this same lens and I'm very happy with the sharpness - much better than the 18-55is kit lens with my 450d (though not as good as my 50mm prime of course).

Your pics look to me like you've got all the focus points active and the AF has picked the branches to focus on as they are the areas of highest contrast.

Switch to center point only AF and I think you will have a pleasant surprise

[T0MAT01]

I hope you don't mind me embedding the original size file for you? (You need to use the insert image button to display the photo in the thread, see the FAQ).

[imglink]http://farm4.static.flickr.com/3116/3170576556_7a12d206c4_o.jpg[/imglink]

I agree that the camera seems to have missed the bird and focused just slightly in front of it - the branch to the right hand side looks to be in focus. In which case it's probably not a lens issue, but that's assuming you had all focus points active when you took it?

[jradley]

I too am using a 450D. I have it set to the centre AF point only and had it set on the bird's eye. I too noticed that the branches look more in focus than the bird and had wondered if maybe the lens had a front-focus fault. However, I'm not sure it is that specifically. I think it may be more a case that the exact focus point (despite acquiring focus lock) is a little random. Also, at the distance I was at I was hoping f8 would have given sufficient DOF, but seeminingly not.

As an aside, I have been very pleased with the 18-55IS and would say it wipes the floor with the 55-250, just no comparison. Hmmm, maybe it is a faulty copy afterall...

Thanks T0MAT01, I did use the insert image button and the tags looked ok but for some reason it didn't work

Cheers,

John

[T0MAT01]

Originally Posted by jradley

I too am using a 450D. I have it set to the centre AF point only and had it set on the bird's eye.

In that case you might like to do a focus test. There's some instructions and a downloadable test chart here. It's written for a Nikon D70, but it applies to all cameras.

HTH.

[loz]

Originally Posted by jradley

As an aside, I have been very pleased with the 18-55IS and would say it wipes the floor with the 55-250, just no comparison.

And I would say totally reverse. My 18-55IS that came with the kit is confined to the back of the cupboard, and I bought a 17-85mm instead.

Whereas my 55-250 is great. see some tests Canon 55-250 - a set on Flickr

[loz]

Originally Posted by jradley

Thanks T0MAT01, I did use the insert image button and the tags looked ok but for some reason it didn't work

you inserted the same url for the link to the page, and for the image.

You need to click on the 'all sizes' option on the photograph, then chose the size you want to paste here in the forum, and then copy the 'photos URL' that flickr provides you further down the page

[Tobers]

Yes, if you locked the focus on the bird's eye, then it looks like the lens is front focusing due to the sharpness of the branches to the right.

You need to try and verify this. I use a simple method to begin with. Find a wooden fence with vertical slats. Stand at 45 degrees to it and focus on a fence post. Look at the resulting image and you should be able to see where the focus is sharpest. It's quick & dirty - lots of people say dont use this sort of 45 degree test, but it'll get you a quick understanding of what the lens is doing.

Try several attempts, all using the largest aperture of the lens and different zoom lengths to see if it is consistent. Dont forget to re-focus each time. I generally focus at something completely different, then focus back on the fence post to ensure the lens is doing its job.

[jradley]

It looks like I might be getting somewhere with this.....

I tried using a focus chart and it does seem as though the lens does indeed front-focus. The results on the chart are very subtle, just a few mm out, but I wonder if at longer range that equates to more distance ?

However, I went through my stack of photos of birds and squirrels in the garden and there is certainly evidence to suggest that items slightly in the foreground are sharper than those on which the focus was intended. I will try the fence post trick tomorrow when its light and see what that shows.

Now all I have to do is try and persuade my retailer and/or Canon that the damn thing is faulty - urrgghhhh.

Thanks for the hints - I'd have never guessed it could be this as front-focussing is not something I'd have attributed to Canon.

Here's the chart photo (cropped):

[IMGLINK]http://farm4.static.flickr.com/3132/3171147298_81caedac28.jpg[/IMGLINK]

Cheers,

John

[Tobers]

Well, 2mm at that close range will make a significant difference if the range is 10x or 100x like in your bird shot. It'll certainly be noticeable.

Suggest an immediate upgrade to a 50D, 5Dmk2 or 1Dmk3 for micro-focus adjustment capability .

[bigtim]

Originally Posted by Tobers

Well, 2mm at that close range will make a significant difference if the range is 10x or 100x like in your bird shot. It'll certainly be noticeable.

Suggest an immediate upgrade to a 50D, 5Dmk2 or 1Dmk3 for micro-focus adjustment capability .

Oh if only it were that simple Tobers! the 55-250mm is an EFS lens. He'll have to buy a 70-200 F4L IS too

S'funny how variable these lenses seem to be - I can almost never get a really sharp shot out of my 18-55 whereas the 55-250 blew me away by comparison.

[loz]

Originally Posted by bigtim

S'funny how variable these lenses seem to be - I can almost never get a really sharp shot out of my 18-55 whereas the 55-250 blew me away by comparison.

yep - that was similar to my experience.

I think the optics are ok, as I could get sharp pictures from the 18-55. But in my experience, it seemed to be the AF that let it down, it just never seemed to nail the focus consistently enough. I just couldn't rely on it.

[T0MAT01]

Originally Posted by bigtim

Oh if only it were that simple Tobers! the 55-250mm is an EFS lens. He'll have to buy a 70-200 F4L IS too

Surely the 50D is capable of 'micro-focus adjusting' an EF-S lens?

[bigtim]

Originally Posted by T0MAT01

Surely the 50D is capable of 'micro-focus adjusting' an EF-S lens?

Sorry Tom, missed the 50D, saw only the 5DMkii suggestion.

Perhaps a 50D is the solution to my poor focussing 18-55is too. Be difficult to explain that one to the wife

[loz]

Originally Posted by bigtim

Sorry Tom, missed the 50D, saw only the 5DMkii suggestion.

Perhaps a 50D is the solution to my poor focussing 18-55is too. Be difficult to explain that one to the wife

I am not sure it is.

In my experience, it was the poor tolerance in the focusing that was the problem with my 18-55 (which is just a cheap mass produced plastic lens...). Hence there was no exact repeatable front focus problem that could be calibrated out. Some times it focused spot on, others it didn't. Micro adjustment won't solve that.

[jradley]

Originally Posted by loz

I think the optics are ok, as I could get sharp pictures from the 18-55. But in my experience, it seemed to be the AF that let it down, it just never seemed to nail the focus consistently enough. I just couldn't rely on it.

I'm still not sure if the problem with my 55-250 is just inconsistency or if it is indeed prone to front focussing - I will do some more thorough tests when I get chance.

It is interesting that more people seem to have issue with their 18-55, which for me has been solid. That said, I tend to use that for more quick snap type photos than anything demanding, but even when my 55-250 gets it right the detail is not as sharp as my 18-55.

I am still thinking of replacing the 55-250, but like I said really not sure what with. I would like more length than the 70-200L, not convinced the 70-300 is a big step up and the 100-400L is probably overkill (and rather more money than I would care to spend) - probably a nice lens though.

John

[mjlamoon]

Try manual focus it helps on shots like this!

[jradley]

To be honest I find manual focussing quite difficult on the 450D at the best of times. Don't know if that's just my dodgy eyes or lack of matte/split focussing screen. When tracking wildlife (eg. a bird hopping from branch to branch) I don't think I would be anywhere near fast or accurate enough.

I'm going to borrow a mate's 55-250 and compare it to mine on a bench test for focus accuracy and sharpness.

As an aside, does anyone know if Canon are about to announce a replacement of the 100-400L ? I'd hate to buy one just before a replacement comes out.

Cheers,

John