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...