Lens Care Question

I have a circular polarizer filter on my 20D's kit lens, 18-55 EF-S, whenever I go outside. How careful do I need to be with these autofocus lens? Do I run a risk of damaging the lens by over-tightening the filters? I've had problems twirling the filter in the field, sometimes to the point of the filter almost falling off, so I had to tighten the filter a bit more snugly, which causes more torque on the mechanism when I go to remore it to put back my skylight for indoor stuff.

How often do you guys go back and forth between filters?

Thanks for whatever help anyone can give me.

photofinish wrote:
I have a circular polarizer filter on my 20D's kit lens, 18-55 EF-S, whenever I go outside. How careful do I need to be with these autofocus lens? Do I run a risk of damaging the lens by over-tightening the filters? I've had problems twirling the filter in the field, sometimes to the point of the filter almost falling off, so I had to tighten the filter a bit more snugly, which causes more torque on the mechanism when I go to remore it to put back my skylight for indoor stuff.

How often do you guys go back and forth between filters?

Thanks for whatever help anyone can give me.

Polarizer for general outdoor stuff? I'd strongly recommend NOT to use a polarizer as a "standard" filter for outdoors. You lose two f-stops and you certainly don't want the polarizer effect in many cases.
Skylight for indoor stuff? I wouldn't do that either. Just for a lens protection, use a lens hood or a UV filter. The pinkish skylight filter may throw off your color balance.

With dSLR, I personally don't use filters most of the times. Polarizers are for special effects (e.g. blue sky) and Skylight is for film to eliminate the blueish cast when shooting on a sunny day.

--Jens--

Thanks for the info. Two issues then.

First, somewhere along the way I got it in my head that the 20D would compensate for the skylight indoors anyway, but I don't know if that is true. So when WOULD you use a skylight filter?

Second, when WOULD you use a polarizer? I've used it to control reflections, especially off water.

I especially use the polarizer outdoors. It removes the glare from surface water, leaves, and other surfaces like cars (windshields especially), and makes the clouds stand out.

The thread issue is something I have fought with for years. One option - when you adjust (spin) the polarizer, do it clockwise so you are not loosening it. You get two rounds of effect for every 360 degree rotation, so the most you have to turn it is a half-turn.

Have Fun,

Yes,reducing reflections off water & windows is a good use for it-probably the most important one.
Reducing contrast is another
Cutting through smoke haze is also a usefull effect

Jerry, I don't think you need to worry about the lens mechanism. If your were to tighten the filter so tight that it would affect the lens mechanism, you would have a helluva time getting the filter back off. I think the lens mechanism is robust enough to tolerate sensible use.

If it is mainly for front lens protection, get a Hoya UV(0) HMC filter. Make sure the lens is clean first, then let the UV take the dirt and cleaning as it is much cheaper to replace than the lens. A lens hood is also a good addition with or without the filter.

Be aware though that under certain light circumstances the filter can give you reflections and aberrations in your images that are sometimes hard to identify as coming from the filter. Otherwise a good UV filter is a help outdoors and anywhere UV is a nuisance.

Experiment.

Thanks for the great advice, guys. CoolToolGuy, thanks for reminding me about the half-rotation thing...John_T, I never knew about the 'reflection' thing with the polarizer. Can you explain more??

Auto WB will compensate.
Custom WB will compensate the best in any situation.

I'd ammend that to say, "Just for a lens protection, use a lens hood AND a UV filter."
Filters are cheap compared to replacing the color coating on a good lens that you'll keep for years. There are times when you need to clean the lens in a hurry & just quickly swipe it with anything at hand. When you wear out the coating on the filter (in 10 years), just replace the filter. I'm still using Nikkors I bought 40 years ago.

Reflections in/on a filter would occur on any flat glass and can compose a recognizable image, whereas on a curved lens it will be diffused or enter as flare. It is sometimes more noticable on night shots. Since the light must come from a certain angle, it is not easily repeatable. Nefarious.

It is not infrequent to see the question come up on different forums, "Where did that ghost come from?" "I didn't see those lights when I shot" Etc.

People answer dirty censor, dirty lens, etc. and the poor guy pulls his hair out trying to trace or repeat it until some guy asks if a filter was mounted.

Doesn't happen often, but it happens. A dirty, cheap and/or finely scratched filter may lightly fog or cause slight color variations in your image. I've had it a few times, but luckily after puzzling for a few moments, figured out what it was.

Thanks, John_T, I did not know that.

A year or two ago there was a thread on FM that went on for seven or eight pages trying to track down the "ghosts" in a guy's image. There was a whole group who were seriously arguing it was real ghosts until someone asked if a UV filter was mounted and spoiled all the fun.

The correct lens hood should practically eliminate any reflections in the filter/lens, though some petal hoods or hoods not specific for that lens might let something through. And BTW, dust on a filter may affect an image more than dust on a lens. Flat surface.

Apart from just getting bluer skies and reducing reflections the CP helps me to get the exposure within the range of the sensor. Now that is important or normally i'd have to bracket the shots. Now that's neat.
Just one issue that i face is i lose some contrast is this the case with everyone or its just me

PhotosGuy wrote:
When you wear out the coating on the filter (in 10 years), just replace the filter. I'm still using Nikkors I bought 40 years ago.

I am not going to start a battle over filter vs. no filter.
But regarding the kit lens, I have used it for three months and I cannot believe anybody will use it for longer than a couple of years. It's optically not a bad lens, if you get a good copy, but it is a crappy piece of plastic and not worth that kind of protection. You rather increase the picture quality with a lens hood than decrease it with an unnecessarey filter for the time you use it. It's not made for a lifetime.

--Jens--

PhotosGuy wrote:
Filters are cheap compared to replacing the color coating on a good lens that you'll keep for years. There are times when you need to clean the lens in a hurry & just quickly swipe it with anything at hand. When you wear out the coating on the filter (in 10 years), just replace the filter. I'm still using Nikkors I bought 40 years ago.

There is one Nikon user, a friend of mine, that has one nice fast lens. Unfortunately, after one shoot, he sort of threw the bare lens back into the suitcase without paying much attention to what might rattle up against it. At the next shoot, he discovered that the outer coating of that lens was scratched, probably by something metallic. In the process of trying to "clean" off the scratch, it got worse. Now it looks bad from the outside, but I don't know exactly how much impact it has on the optical transmission. If he had used a simple UV filter, then if it had gotten scratched, he could simply throw it away and get another one cheaply. But a fast lens is something different.

Don't hold it against me if I have a Nikon user for a friend.

---Bob Gross---

Bob:
I can refere you to a 12-step program for people with Nikon-user friends. The first step is admitting you have a problem.

Too bad about his lens. If there is a bright side to the story, it's this: it wasn't your lens.