How important is a CLS filter?

I'm thinking about purchasing a wide angle lens in the near future. I will be doing mostly landscape photography (I think), but also want to try some astrophotography. I know that the Astronomik CLS clip in filter won't fit behind the Canon 10-22, but the Tokina 11-16 has issues with flaring for landscape photography. I'm wondering, how important is the CLS filter? Can I get decent shots without it, or is it pretty much a necessity?

Thanks very much.

The Astronomik CLS filter blocks some of the wavelengths that cause light pollution. So whether it is necessary or not would depend on the amount of light pollution at the location you are imaging at. Also, if you are doing shorter exposures (less than 30 seconds), it is probably not as useful than if you were doing longer exposures.

Flare shouldn't be too big of an issue when you are doing astro shots.

nu8reed wrote in post #14446478
The Astronomik CLS filter blocks some of the wavelengths that cause light pollution. So whether it is necessary or not would depend on the amount of light pollution at the location you are imaging at. Also, if you are doing shorter exposures (less than 30 seconds), it is probably not as useful than if you were doing longer exposures.

Flare shouldn't be too big of an issue when you are doing astro shots.

OK, thanks very much.

I'm more concerned about flare with regards to landscape photography during the day. Deciding between the Tokina 11-16 and the Canon 10-22 is tough... but that's a discussion for the lens forums.

shedberg wrote in post #14446201
I'm thinking about purchasing a wide angle lens in the near future. I will be doing mostly landscape photography (I think), but also want to try some astrophotography. I know that the Astronomik CLS clip in filter won't fit behind the Canon 10-22, but the Tokina 11-16 has issues with flaring for landscape photography. I'm wondering, how important is the CLS filter? Can I get decent shots without it, or is it pretty much a necessity?

Thanks very much.

The CLS filter is not mandatory and is required mainly to avoid light pollution. If your area has lot of light pollution then during long exposure the sky turns red / orange and frame gets bright without any details from sky. with CLS you avoid light pollution from Sodium Vapor and some Mercury lamps, it basically blocks yellow-orange part of specturm allowing more contrast to astronomical objects.

If you are thinking of just Tripod mounted long exposure for Star Trails and not planning for long exposure photos with astronomical mounts which tracks the camera with moving earth, then you may not need CLS.

From dark sky you can get very good photos without CLS filter and very few people really use CLS. Also there are some issue of color balance with CLS as it excludes yellow orange part of spectrum. You need to shoot with Custom White Balance and then also may need to tweak color in PP.

Regards