filter information

[topsparks.42]

I recently purchased a second hand sigma 20-40mm 82mm diameter aspherical lens, I need to buy a lens protector/skylight uv filter. The problem being, the lens is curved which prevents a filter screwing down properly.

Can you get a 82mm to 82mm extention for a 82mm filter to stop the filter from touching the camera lens?

I'd prefer not to use step-up or step-down extensions.

I hope this makes sense.

Thanks.

Topsparks

 

[PatrickHMS]

The following is just one man's opinion, and subject to others here disagreeing with me ~

You already should have a "lens protector", called a lens cap.

A filter is good mostly when you want to alter the image to be recorded in the camera, but even a clear "lens protector" will alter/affect image quality when it is on the lens whether you want it to or not.

Learn to be careful, shoot with a clear lens (without "protection") and you should get consistently better photos over the long run, then put the lens cap on to protect glass lens surfaces when you are done shooting and put the camera up.

Over 40 years of film shooting I amassed a large collection of photo filters, but I only use a few with a DSLR (CPL, ND Series, cross-star filters), as most filter effects can be duplicated in PP software.

All of the colored filters (blue, yellow, red) were mostly designed for b/w film.

As far as I know, most DSLR's already have a UV filter inside the camera, in front of the sensor.

 

[Garbz]

Here's another man's opinion (and you'll get many opinions on this forum since this is really a personal taste question like mmm liquorice vs yuk! liquorice!)

Don't coddle or protect or be careful with your camera. If you're camera's not dangling loosely around your neck while you're scaling a cliff-face you may miss that perfect shot half way up. A protective filter has saved my lens on more than one occasion.

Anyway an "extension" ring will not work. By bringing your filter up a bit it's going to cut into the corners of the frame at 20mm. The stepup ring is actually a good idea. However that said it will block your ability to put a lenshood on. If the hood is like the one on the Sigma 10-20 you won't miss it, but if it's like the hoods on say the 28-70mm and really long then it may do more to protect your lens than a filter would. In this case I know which option I'd be picking.