I think you've nailed it Roy! Sharp as a tack.

It's the filter. Think back to your first (terrible!) barcode shot: OK, it was hand-held, but at a 2000th of a second it stil should have been a country mile sharper than it was. But this one is as good as you could ask for. Ypu will need to test further to confirm, but I reckon you could re-shoot the barcode handheld now and find it's pretty close to just as good.

Let's find out!

You are right Tannin - attached is hand held 1/1000. looks pretty good to me.The filter will be ditched, guess if I always use the built-in hood then the glass will be protected anyway. Many thanks to you, Rob and everyone else.

Cool! Now you have one more job to do: point that 400 at some birds!

I don't think that filters are always bad - the one on my 10-22 stays on all the time and though I've never tried the lens without it I get excellent image qualiy with it just the same. But that is a good quality one (still Hoya, but maybe two or three times the price of their cheap ones). I guess the lesson here is that cheap filter bad, good filter OK.

My cheap Hoya close-up lenses .... well ... I tried them out two weekends running and have never used them since. (Bought a 60mm macro lens instead, which I haven't learned to make the most of yet.) It was something familiar about that weird distortion in the gull shot that suddenly reminded me of my results with the close-up lenses and made me think of filters.

Anyone want to by two sets of close-up lenses? 77mm and 58mm, three lenses per set. As-new condition, going cheap!

So, depending on what the experts here think, I guess you could buy a top-quality filter for your 400 f/5.6 and get very, very close to the same results you get with the bare lens. Or, as you say, you could just keep the hood extended and take care. FWIW, that's what I do with all my lenses except the 10-22. (I make the exception for the 10-22 because the front element is so bulbous and exposed, even with the lens hood on, that I just don't think I could rely on keeping it in pristine shape. If I scratch the filter, so what, I've blown $60. Scratch the lens and I've blown $1100. Big differece.)

Very pleased to see you getting the results the lens deserves at last.

Glad you have managed to sort the problem out. I also run some tests on Mario's 100-400 IS lens he hasn't had many keeper which we put down to his shakes, well I saw a big difference. On mario's 100-400 IS lens there could be the same problem because when I removed the filter every photo was a keeper. The one on my 170-500 seems fine so not removing that one.
We also have the cheap filters on most of our lense.

Thanks Christine. I have had a filter (cheap jessops one) on my 70-200 f4 L for a year now and that lens as always been pin sharp which is why I automatically put one on the 400 prime. I Just need to get out nail a few birds now.
Roy

Interesting reading.I have a basic Hoya filter on my 400 lens,mainly to protect the lens from sand grit etc,so does this mean I would have sharper images if the filter was removed?.It is only the basic filter.

I think it's a case of trying it Christine. I don't use a fitler on my 300 or 24-70 as they both have lens hoods. I am not near the coast so no great worries about sand grit. I did bash a lens some time back and the filter broke and scratched the lens front element. Since then I've not seen filters as a life saver.

I have a cheapo Polarising filter which gets used once in a while but there have been one or two occassion when I wondered if the filter was responsible for some soft shots. I never gave it too much thought. I tend to begrudge paying top Dollar price for a filter I hardly use.

I used to use a skylight filter on the front of every lens I owned. After 20 years of never bashing a lens (except for the time my 100-300 rolled off the dining table, when the inclusion of a filter didn't make a ha'peth of difference), I decided not to buy a filter for my dSLR kit lens. The images were sharper that I used to get from any of my film SLR lenses which made me think. I put a reel of film through the z-50p using the truly awful 35-80 kit lens it came with, some shots with filter, some without. This lens is bad anyway, but the filter really made things a lot worse.

I'm highly unlikely to ever use a filter purely for protection again. I'm careful with my kit, don't bash it around, and I don't possess mega-buck lenses anyway.

It also fits into my kit-bag easier (it's a tight fit with everything in there), that few mm less makes all the difference.

Duncan

Having read the comments on the degrading effects of filters, frankly I just didn't believe it, so I decided to carry out my own tests. I used a canon 100/400 mm lens at f5.6 and 1/320 s on a tripod and using an electronic release. Light did not permit a faster shutter speed even at 800 ISO. The filter was a Hoya HMC Super Pro 1 and it was clean!. The shooting distance was 10 m. The results have absolutely astonished me. From now on it's good-by filters. Results are maximum quality jpegs straight from the camera, no post processing except crop.

John

Wow - John the difference is obvious even from the thumb nails...

Gosh,John,this really does make one sit up and think twice!!!.I mainly keep a filter on the lens,a-as I have prev mentioned,sand and grit,b-it is easier cleaning a filter,no great damage done if scratched,cheaper to replace a filter,than the lens.I'll have to have a practice and compare the results.

Goodness that took some resolving! One thing about filters is that if the quality is not as good as the glass on your lens then your money is wasted. For bird photography I never use a filter and use the lens hood as protection.
As for focusing I am surprised no one has mentioned AI servo. This it the tracking focus and is present in all modes on the 350d. I use the 350d and the 400mm f/5.6L and there is nothing wrong with its sharpness. It is the sharpest lens on the market.
As for isos with this lens I have rarely had to use any iso higher than 200 as it is fast and lets in alot of light. As others have already said practise is most important as are your camera settings as the correct aperture will also affect your focusing. This lens is very good wide open providing the compensation is right. I think alot of people struggle because they are overexposing. It is surprising what an extra stop under exposed can do to focus.
A shutter speed of 1/500 is plenty fast enough for still/perching birds and 1/800plus for birds in flight. Increasing the iso will only lead to degradation of picture quality and should be avoided. Practise is the real key. I have taken the photo below just now of a siskin on a feeder. it was taken through glass with the feeder swining in the wind. Taken at iso 200 f10 (to narrow field of focus) shutterspeed 1/800 and although there is some loss of quality due to filthy windows it is perfectly sharp. This was handheld and is perfectly attainable by anyone.

That's disgusting. I just bought filters for both of my lenses. I had always used filters on my 35 mm lenses. Now i think that I'd better run some tests of my own. This may explain the softness in the junco picture that I was talking about the other day.
Great discussion though. Well done, guys.

OK, I ran some tests. I won't post the pictures but here are results.
The first thing that I learned is that automatic focus/auto exposure gives me a disappointing result regardless of filter or no filter. When I switched to full manual exposure and focus I found a slight improvement when shooting without the filter. Camera Canon 20D. Lens no. 1 is a Caono EF-S 18-55mm f3.5-5.6 (came with the camera). Lens no. 2 is Canon EF 75-300 f4.5-5.6 lll USM. Both filters are Hoya HMC UV(O) (these were the most expensive ones in the shop)(also the only ones that would fit my lenses).
If anyone wants to point out that there are better lenses out there, I believe you but these are the ones I could almost afford. Upgrades may take place some day if I live that long.

Snowyowl auto settings will nearly always give disappointing results no matter what you are photographing as it just isnt accurate enough and often tends to over or under expose. Less that six months ago I used exactly the same outfit that you are using now without a filter and got excellent results. The 18-55mm is great for close up work though i never rated the focus for landscapes. I think it really needs a tripod for best results. The 300mm usm maynot be as fast as the more expensive lenses but should still give excellent sharpness in the right conditions. In my view successful photography isnt about using expensive equiptment (although obviously these can make it easier) but it is all about the way it is used. Anyone can get the very best from lenses if used properly.

Annette you are so right. I came across a website a little while ago that I think help put it into perspective for all of us who want that longer/faster/fancy optic lenses, which was written with medium format film cameras in mind but the principles hold good I think. http://medfmt.8k.com/bronlensenvy.html (but it still doesn't stop the hankerings does it :D )

LOL Clive indeed not. My philosophy has always been to learn what the lens can do to its full potential. I think too many people do not know or learn what their lenses can really do. If money were no object i would not hesitate to buy the 600mm f4 for my bird photography but even with those there are tradeoffs and so I content myself with what i have already.

I can see you are using a UV filter by the lines in the background, try it without it you should see a difference. Also try center wieghted & single point focus.

Roy,send us a copy of you bank card,both sides so we can compare !For you and all canon owners ,this is a canon eos site and run by canon EOS there is much help ,it is a forum site only and i have got plenty of help from it,
www.eos-forums.com
it is a free site and you will get a lot of help there are experts on it !
cheers.Tony.

Ho Cashie, For info this problem was sorted a long time ago, turned out to be a duff filter.