Question on CPL usage

[Milhouse]

I just bought some stuff and had a couple of questions regarding my filters.

1. I purchased both a UV and a CPL. I have the UV on right now, when I want to use my CPL can I just screw it on top of the UV or should I remove the UV first.

2. My CPL (Hoya) has a white notch on it, to help with orientation. What direction should the notch be placed for maximum and minimum effect. (I haven't had a chance to test it)

3. I've seen 1 post that said that my AF will not work with a CPL and another that said that it wouldn't work with a LPL. I probably read the posts wrong, so if someone could shed light on the subject for me I would appreciate it. Just a FYI the front of my lens rotates.

Thanks

 

[The_Traveler]

remove the uv
CPL is fine.

 

[Helen B]

A circular polarizer is a safe bet. Polarized light can affect the exposure meter or autofocus sensor inside your camera. In simple terms a circular polarizer is a linear polarizer followed by a depolarizer, so the light coming out of it is not polarized. It doesn't behave perfectly, but it's near enough.

You can see the directional effect by looking through it when it is off your camera. If you look through it the right way round it should work properly. Look through it the wrong way round and it should only work partially.

You select the orientation by simply looking at the scene with the filter on your lens and rotating it, after focusing or zooming of course, because of your rotating front. There are some cameras that don't have reflex viewing through the taking lens (ie they aren't SLRs). Marking the filter helps with alignment - you can look through the filter, note the alignment, then attach it to the camera at the same alignment.

Best,
Helen

 

[rmh159]

I have a filter I use on my lens to protect it (assuming that is your purpose for the UV filter) so I just leave that on if indoors and replace it with the CPL if outdoors. I wouldn't stack a filter though if it's just used for protection and not an effect.

Plus if it's sunny enough you'll see the effect increase / decrease drastically as you turn the filter. Just spend a minute looking through it and figuring out where the darkest effect is achieved and then check out where the marking is. It shouldn't change from shot to shot unless you turn the camera on its side of course.

 

[Joves]

Remember you wont need to max out your CP all the time. I just adjust mine for what I am shooting. When you have a nice clear day but, there is haziness at the edges of the sky, I max it out. It will clean it up quite a bit sometimes, depending on how thick the haze is.

 

[Jon0807]

Sorry to hijack the thread but is there a reason not to stack a UV and a CPL? I've done it with mine and haven't noticed any ill effect from it. I usually keep the UV on my lens to protect it and having to keep taking it on and off when I wanted to use the CPL just seemed to be too much of a hassle. I'm probably just being lazy but if there's a reason not to stack then I'll do it.

 

[JerryPH]

Depends on the quality of the UV filter. Sabbath made a nice post showing the advantages of getting quality filters over the $20 ones.

 

[Milhouse]

Thanks guys, I wasn't expecting this many answers. One more question about the CPL. How much would I have to turn the filter to change it from min to max effect, 90 or 180 degrees. I would think that a 180 degree turn, just turns it upside down and thus the same effect.

Just for some clarification on the UV CPL stacking:
I was just using the UV as protection, and since I'm lazy I was hoping that I could just put the CPL on top, instead of fumbling with the filters.

 

[Joves]

You can stack them but, it depends on how high it stacks them. It way vigenette slightly in the widest focal length on some lenses.

 

[Socrates]

Thanks guys, I wasn't expecting this many answers. One more question about the CPL. How much would I have to turn the filter to change it from min to max effect, 90 or 180 degrees. I would think that a 180 degree turn, just turns it upside down and thus the same effect.

Just for some clarification on the UV CPL stacking:
I was just using the UV as protection, and since I'm lazy I was hoping that I could just put the CPL on top, instead of fumbling with the filters.

Min to max is 90 degrees. However, don't get hung up with details like that. Turn it while looking through the viewfinder. Keep turning until you get the effect that you want.

Regarding multiple filters... That's really a bad idea. It increases internal reflections substantially which reduces color saturation and, in some cases, causes visible flare.

 

[Flatland2D]

To answer your question about the marking on the ring, you rotate that so that it points towards the light source (the sun). So from your perspective behind the camera, if the sun is to your left, the marking should be at the 9 o'clock position. Turn the ring 90 degrees to remove the effect.

Someone correct me if I'm wrong on this one, but I believe the maximum polarization effect you can get is when the sun is 90 degrees from the direction of your shot. For instance, at sunset, you will get the greatest effect facing north or south with the marking pointing west.

 

[Tayfun]

I agree with Socrates. As he mentioned multiple filters can cause flare caused by reflections between them. Also can cause vignetting on the photo. Also will force you to shoot in lower speeds. As my opinion for protection use UV, and replace by CPL when needed.