Lens protection

[Freako]

Just received my new 100-400 is lens, should I be using a filter to protect the glass? If so what? Mick;)

[JohnZ]

Been a few threads on here claiming that filters affect the quality of the image. I have the 400mm prime and use the lens hood, built in, but I believe that the 100-400 does not have this facility ?
Even if the lens hood is detachable I would still use that myself. Should be deep enough to protect the front glass.

[kawwauser]

my 100-400 came with a protective hood et-83c bought from warehouse express,this is what it looks like http://www.amazon.com/Canon-83C-Lens-100-400mm-4-5-5-6L/dp/B0007NIB74

[tdodd]

I'm very much in the hood only camp. I have a Hoya Pro 1 filter, in case the conditions are severe - flying mud or stones from a rally, for example, or in a dust storm, but I see no need to stick another piece of glass in front of my £1,000 lens unless I have to. The hood is quite deep and offers pretty effective contact protection.

[Freako]

Thanks Guy's, I will stick with the hood only:t:

[K-Lex]

As I've said on another thread, if you stick a UV filter in front of the lens, you're devaluing the optical performance of the lens to the price of the UV filter. The only time to have a UV filter on is when you're getting blasted by salt water/sand etc. Any other time, take it off.

[tdodd]

I just shot a series of three test shots with my 100-400 at 400mm, 1/1600 and f/5.6 on a tripod. Subject distance was approx 10m - a realistic working distance for this lens. I used Live View and focused manually to get the best focus I could and, using the 10 second timer, fired a shot with no filter. Without changing any of the setup I then screwed on my Hoya Pro 1 Digital UV filter and fired off another shot.

I compared results on my laptop and saw a distinct deterioration in IQ with the filter attached. Wondering whether the filter might have caused a focus shift I tried refocusing manually with Live View and 10X magnification, and fired off a third shot, again with the 10 second timer.

I have attached 100% crops of the raw files with no sharpening at all. These were shot in neutral picture style, with camera sharpening parameter set to 0, and these are straight crop and convert jpegs.

If you look at the fine text of the password "WINEBANK" I think the deterioration is quite evident.

The fourth image is the bare lens without filter, but with sharpening set to 3 in DPP and picture style changed to Standard. The fifth image is the shot with the filter attached and manually refocused and again sharpened and with Standard Picture Style.

Image 1 - no filter, unsharpened
Image 2 - filter added, not refocused, unsharpened
Image 3 - filter added, refocused, unsharpened
Image 4 - as image 1 but sharpened
Image 5 - as image 3 but sharpened

[tdodd]

Just for some context, here is the original full frame image with no filter but with my standard edit of PS=Standard and sharpening = 3.