Do UV/Protection Filters degrade image quality?

I have always been using 58mm Canon UV Filters on my Canon lenses

such as the 28-105 f/3.5-4.5 and the 50 f/1.4 and so on. And I have

recently shot a few pictures without the filter on my 28-105. I am

looking at them and I see one taken in a scene with it on and one

taken in the same scene with it off and there is less grain and

better color reproduction in the photo without the filter. If I use

my lens cap alot I don't suppose it is really nesscessary to keep the

filter on for protection? Am I just seeing things or do

these "clear" filters actually degrade image quality somewhat?

Indeed, a filter will affect the optical quality of your system to some extent. Even the best filters will alter it slightly simply because you have another piece of glass in the way.

 

If you are comparing prints made at a lab however, I couldn't tell you if you're seeing a difference due to the filter or not. Grain wouldn't be affected, although color rendition can be. The best way to tell is to shoot slide film, preferably on the same roll so its the same batch of film and developed at the same time.

 

I do tend to keep a good UV filter on many of my lenses depending on what I'm shooting.

 

In this case you're probably seeing things. Prints made at labs, even pro labs aren't completely consistent. There's no way to guarantee that the print you've received is as true to the original as possible.

Personally I've never noticed any image degradation when using a UV filter.

 

However I think there should be a distinction made between a UV filter and a protection filter. A UV filter is designed to filter out UV rays, and so reduce the bluish haze associated with landscape shots on sunny days. Therefore, you could notice a difference in colour rendition between the filter and non-filter shots.

 

A protection filter, on the other hand, is just that. It's clear glass that doesn't attempt to add or subtract anything from the subject. It's sole purpose in life is to protect the end of your far more expensive lens from salt spray, flying rocks, greasy children fingers, bird crap etc.

 

Nik

If your only concern is grain and color reproduction, then you should mount the camera on a good tripod, and shoot comparable frames (with / without filters) on good slide film at a few different focal lengths, with the sun to your back. Preferably, with both high and low contrast scenes, and at least one shot with as many vivid natural colors as possible. As you start to control all the variables, you might find it hard to distinguish the frames. Unless a filter is mislabeled or defective, you should not be able to see it degreading the image if you control for variables - certianly not on minilab prints, and perhaps not even in projection. Of course, skylights and UV and such do different things, but they should not bear on grain.

"Personally I've never noticed any image degradation when using a UV filter" - I did. I always use the lens hood when the lens is used and the lens cap when it's in the bag. Never had any problems.

If you use a UV or Skylight filter primarily for lens protection, you should always use a lens hood since the filter increases the danger of flare affecting your pictures and the lens hood will help prevent it. What you may be seeing in your comparison shots is flare causing the loss of color.

>>>>>>>>>> If I use my lens cap alot I don't suppose it is really nesscessary

to keep the filter on for protection?

 

Using your lens cap a lot isn't exactly safe, quite the contrary :) If you snap it

off and on a lot, this statistically increases chances of touching the lens with

the edge of the cap, which also has a few pointy extensions... you get used to

the movement and you end up not looking when you're putting it on... At least,

I've experienced it.

 

You want protection?

Get a hood. Hoods are something people don't use enough. Besides cutting

on flare, hoods improve side sharpness in quite a lot of situations. A hood will

allow you to get rid of the UV and use it only when it's really necessary....That

legendary "table corner" (or whatever) which is the reason for which many

people keep their UV's always on will be kept out of the reach of your lens

front element also by the hood.

1) Filters do not protect lenses from impact, in fact if the filter glass shatters chances are a shard will scratch the lens.

 

2)The people who advocate using lenscaps and hoods for protection are missing the point of UV filters. Read on...

 

3) Filters *do* protect lenses from coating scratches caused by dragging an unseen speck of grit across the surface while wiping it clean. These "wipe marks" do much more to degrade images than any UV filter, and they kill the resale value of the lens.

 

4) Uncoated and single-coated filters cut light transmission and lower contrast, and can introduce flare and ghosting from strong light sources inside or just outside the picture area.

 

5) B+W MRC Multi-Resistant-Coated UV filters are so well coated that it is often difficult to tell there's glass in the mount. I have used them since their introduction and have yet to have an instance of flare or ghosting even in strong backlit situations and leave them on even with other filters in place (except ultrawide lenses if they vignette); nor have I had one develop scratches even wiped with a Kleenex, a paper napkin, or my shirttail. I have one on every lens I own that takes a filter.

When I am shooting in "peopole" situations, image quality is not of primary importance. I have a lens or two in a shoulder bag, and I am slapping them on and off the camera. For speed, they are in the bag without lens caps. I would not dream of doing this type of shooting without protection in the form of a UV or haze filter. Too bad I can't put one on the BACK of the lens too!

 

When I am shooting landscapes, image quality is of primary importance. I have plenty of time to have good technique, so I don't need lens protection.

You're seeing things.

 

A filter has nothing to do with the grain in a photograph. A UV filter, under certain circumstances, should actually IMPROVE the colors by removing some of the UV light. That does, of course, depend on the strength of the UV filtration which is only minimal in most "Haze" filters.

 

Erwin Puts, Leica lens guru (www.imx.nl), is a fanatic concerning optics. He apparently feels there are no lenses to compare to the current Leica lenses and offers laboratory findings to confirm this opinion. On the subject of filters, Puts has stated the use of a filter causes less image degradation than is commonly believed. He says handholding a camera during picture making causes more degradation of the image than using a filter for protection.

 

Don't be obsessive about filters. Use them or not, as you prefer.

I agree with Puts on one thing, and that's the subject of filters. You do get what you pay for however and if you purchase the cheapest, uncoated filter you will pay the price. I never bother with the cheap filters but my friend recently started buying better multicoated ones from brand name unmentioned and the sharpness improved drastically as his cheap one wasn't optically flat.

From my experience, yes, filters degrade image quality. And yes, you can see the difference with print films. A good filter definitely helps though.