Filters - what to use

Hawk66 · 23-01-2007, 18:16

I'm just about to buy a skylight, mainly if I'm honest to protect a new lens that I've just bought, but im wondering if Im better off with something else like a polarising one.

Whats the best for almost permanent use and why? It will live on the end of a Nikkor 18-200mm VR

Thanks in advance and regards

Neil

P-E · 23-01-2007, 18:31

It's always down to personal choice but I always have a UV filter on my lenses.

I have a mixture of multi coated slim Hoya ones and B+W.

danpen · 23-01-2007, 18:32

If it's for protection and semi permanent mounting you need something that's going to have minimal imapct on the image and image quality. So while you may want a polariser for specific purposes you want a reasonalbe quality UV filter for this.

Hawk66 · 23-01-2007, 19:02

Thank you for the comments.

I think ill go for a UV filter for general protection duties then. Are there any particular brands to go for or to avoid? I was thinking Hoya...

Going back to the polariser what is the advantage of a circular polariser?

Thanks

Neil

P-E · 23-01-2007, 19:10

Some useful info here.......click on the Filter Information.

Warehouse Express - Photographic Equipment, Digital Cameras, Lenses and Accessories

Les Meehan · 23-01-2007, 19:23

If you intend to go for Hoya might I suggest their Hoya 1B in the Super HMC Pro 1 range. Be prepared to spend money on this as cheap UV filters have two problems:

1. They are optically bad so are a waste of money
2. They don't work as UV absorbers! Many UV filters actually behave like florescent paint and increase the amount of UV. I have seen this using a UV lightbox and a range of different UV filters. Only the Hoya 1B went darker (absorbed UV) whereas the others glowed! I stress these were cheap, but typical of what many use, brands.

Pay your money and get the best you can afford.

lolyton · 23-01-2007, 20:56

Another point to remember, if you are using a filter such as a UV filter (which is a good idea and will protect your lens more than anything [though i don't tend to use one on my expensive lens... God knows why not as i have them!])
If you then want to add another filter (especially a circular polariser as these tend to have extra depth) you may find vignetting will occur at the wider regions of your lens...unless you take off the UV filter first (also more filters leaves more chance for optical flare).
I have a fairly wide lens, just a little wider than the one you have mentioned and i get vignetting with only my circular polariser on. (if it's an internal focus lens you should be able to buy a linear polariser which are cheaper so you can get a better one)

Liam O'Neill · 24-01-2007, 00:19

Linear polarisers will prevent enough light reaching the AF and metering systems on most modern SLR's, you need a circular one.

lolyton · 24-01-2007, 14:39

Quote:

Originally Posted by Liam O'Neill

Linear polarisers will prevent enough light reaching the AF and metering systems on most modern SLR's, you need a circular one.

Maybe for glum ol' England!

Liam O'Neill · 24-01-2007, 17:58

Where you are or how birght it is outside don't come into it. The camera splits the light and sends some of it to the viewfinder and the rest to the AF/Metering systems. The way it splits the light doesn't work with linear polarised light, but does with circular polarised light.
A very quick search on google will show you hundreds of sites that say so.

lolyton · 24-01-2007, 20:02

Sorry Liam, you are of course 100percent right, i was just being flippant.
A quick light meter reading and using MF (i rarely use AF as i like to focus on what i want not what my camera wants) will sort it tho!

Liam O'Neill · 24-01-2007, 23:46

It will

I just wanted to make sure someone reading this thread didn't think they could save a bit of money with a linear polariser only to find causing trouble for them.

abirkill · 25-01-2007, 09:21

Worth pointing out that it's not as simple as a lack of light per-se, it's varying light depending on the position of the polariser. The partially-reflective section of the mirror that passes the light through to the AF and AE modules also polarises the light when doing so - this means that the amount of light reaching the modules varies depending on the rotation of the externally-fitted linear polariser.

Depending on where it is positioned, you may find that your AF and AE systems work perfectly with a linear polariser, but when you rotate it they become unreliable - i.e your linear polariser is set to polarise the light vertically but the mirror only allows horizontally-polarised light through.

A circular polariser is a linear polariser which is in front of a quarter-wave plate - the linear polariser polarises the light as required, and the quarter-wave plate then unpolarises that light. This means that you get the linear polarisation effect but the light that reaches the camera internals is unpolarised. This is also why circular polarisers have the curious effect of only working when you look through them from the right side.