DUMB question about lenses/filters

[RBennett]

OK, so if you go with another brand of lens or filter than your camera, how do you know if it will work? For instance, I have a Pentax K100D, (I can actually say that now!!! ) but if I decide to get another lens other than Pentax, how do I know they're compatible?? Also, how do I know what size filters to buy?? THANKS for any help!!!!

 

[ukcatfan]

You need lenses for a Pentax K mount. The K mount has been around longer than I have been alive, so there are many lenses for it floating around and a pretty good selection of new ones as well. Off the top of my head, here are some 3rd party lens makers that have Pentax models: Sigma, Tamron, Tokina, Phoenix, Cosina. Carl Zeiss also recently announced that they are going to start making Pentax K mount lenses, but expect them to be expensive. You will want to find a review of a lens before buying it as there are some bad oens out there. Here are a couple of sites:
http://www.photodo.com/products.html
http://photozone.de/8Reviews/index.html

For filters, often they have a spec called filter size. You might also see something talking about the size of the front element. The kit is a 52mm filter and the 50mm takes a 49mm filter. To save $$$, you could get a 52mm filter and a 49 to 52mm step up ring. You run the risk of some vigenetting with this option though(dark corners). My 50mm is a f/2 and it is fine with a step up ring, but at f.1.4, your's might show it.

Kevin

P.S. You will likely not find any filters made by the camera makers. I prefer Hoya filters, but there are other good brands. Look for the key word "multicoated".

P.P.S. Hoya just bought Pentax a couple of months ago.

 

[RBennett]

One other question regarding filters, what exactly is the purpose of circular polarizers? I mean, in what conditions do you use it? Any time you're shooting into a shiny surface, whether it's water or glass or do you use it in other situations??

 

[handicap18]

You can use it on really bright sunny blue sky days in the middle of the day. Typically the middle of the day is not the "ideal" time for photography because of the location of the sun and the shadows and bla bla bla. Using a circular polarizer you can get a more evenly exposed image. Say your taking a landscape pic and the landscape part is exposed nicely and the sky is blown out because of all the light. With the CP you can rotate the filter so that the darker part of the filter covers the sky, therefor making the camera think that there's not as much light and you still get the same nicely exposed landscape and the sky wont be as blown out. It will give the sky a darker blue appearance. There are other times too, but thats all I got right now.

 

[MarkBarbieri]

I find a polarizer useful when there is a lot of blue sky in the shot. It helps saturate the blue. I also use it to remove reflections in glass, water, or metal, or any flat surface. I avoid it when I need the extra light.

It can be useful in removing glare in more situations than you might think. Take shooting a tree for example. In many cases, you might be getting small amounts of glare off of the leaves. The polarizer can help with that.

My advice is to just keep it on your camera when you'll be shooting a lot of shots outdoors. Fiddle with it and see how it affects things.

At Disney, it's a tough call. I find myself going into and out of low light situations so often that it's a nuisance to keep putting a polarizer on and taking it off. Maybe someone needs to come out with a snap-on polarizer.

 

[Groucho]

Also, if you're looking at Adorama's or B&H's site, you can filter down to just Pentax-mount lenses. They usually have a reasonably complete selection of what's out there, not counting import lenses like the Zenitar 16mm fisheye, of course.

I prefer looking at Adorama's site because B&H separates out film lenses and digital-only lenses, whereas Adorama lets you choose that later on, so you don't have to look in two places to see all the available lenses.

We'll be getting new Zeiss lenses in Pentax K-mounts in a few months, too... fun stuff!

As for circular polarizers, I think a lot of the usefulness is that it shrinks the dynamic range of a scene - by darkening the sky, it makes it less likely that the sky will be "blown out", ie, just a big white blotch. This is obviously not a concern if the sky isn't in your photo, or if the sky is dark. At that points, its benefits are being able to control reflections.

With the CP you can rotate the filter so that the darker part of the filter covers the sky, therefor making the camera think that there's not as much light and you still get the same nicely exposed landscape and the sky wont be as blown out.

Your description kind of sounds more like a neutral density graduated filter, where one side is light and the other is dark. A CP is uniformly dark.