I am about to purchase a circular polarized filter for my my 28-70mm f3.5/4.5 lense. The question I have is I use a UV filter on this lense, do you think I will encounter a problem using both filters at the same time or should I remove the UV filter and just use the Polariser? Unfortunately I will be leaving for a fishing trip on Saturday and I don't have time to try out different combinations.
When you are using the polarizer take the UV off. It is not usually a good idea to stack filters as you may end up with some vignetting- cut off in the corners- particularly with shorter focal lengths. Each extra layer of glass or plastic/resin you put between your subject and the film also carries the risk of degrading the image. Your polarizer will also have UV properties, as will any other warm coloured filter. hth
I think it's also dependant on the type of polarizer: if you're using a linear polariser, the effect will show up. I'm not sure whether a circular polariser won't cause a gradient, and concidering the way it polarises light, it -probably- doesn't, but I'm not 100% sure.
How wide: around 24mm and less (80 degrees and more) will do the trick.
It's also dependant on how low the sun is, and what the angle of your lens to the sunlight is. Luckily, it's also visible in your viewer, but it can be a nasty effect.
Never experienced this problem in any of my lenses and I have been shooting for many years with polorizers. Not saying it doesn't happen, just I have never experienced it, but now I will look to see if I can duplicate it. As for linear polorizers; back in my Triassic period (I'm currently in my Jurassic period, heading for the Cretaceous period):-) , I did use linear polorizers, but can't remember if I had gradient lines in photos or not. Of course, my skills back in those days, was not what I believe they are now. Currently, because of AF cameras, linear polorizers are hardly ever used, since they confuse the AF system. Have a great day...DD
You will run into the problem Mike mentions using both circular and linear polarizers. The cause is not so much the angle of view of the lens as it is the angle at which you are relative to the sun. Polarizers are most effective when used at 90 degrees to the sun, at least for getting deep blue skies which is where you get this problem. If you include areas of the sky which are to close to the sun, more likely when using wide lenses, then the effect of the polarizer on that area will be lessened. To cut a long story short, what you can end up with is a dark blue sky at one side of the frame graduating to a lighter blue at the other. To go back to something Mike was discussing in an older thread about using polarizers as variable ND filters, if you use a modular/square system you can mount two linear polarizers in tandem and rotate one relative to the other for that purpose. Apparently this method will not work correctly using circular polarizers.
Thanks Alistair. I now fully understand what Mike was saying; however, since this affect happens with or without a polorizer filter on the lens, I guess I got perplexed as to what Mike was explaining. As the following picture will show, the blue sky naturally darkens away from the rising (or setting) sun. If I had used a polorizer filter, it would have enhanced the blue in the sky, making it more evident than it is in this photo. This picture was shot in October '97, in the morning without a polorizer filter. As you can see, the sky goes from light blue towards the east where the sun is rising to dark blue to the west. I walked down the road with camera and tripod, a good mile, to see what type of photo I could get. After setting up the camera on the tripod, I then noticed...no polorizer. Since I had been up since 4:30 to get situated and get some sunrise photos, I was tired. So I took the shot anyway, bracketing five shots. Since it was still rather early, I was lucky there was not much traffic. In addition, as you can see it's October and the trees had not turned yet, so I was a little upset with that fact too.