UV Filter with green color - DPChallenge Forums

Canon EF 85mm f/1.2L II USM

05/03/2013 10:47:59 PM · #1

I got a Rocketfish UV filter (bought from BestBuy) and noticed that when I use UV filter I see a green color around white color bulb where as without the filter there is nothing.

Is this something to do with UV filter?

With UV filter:

Without UV filter:

Cory

Canon EOS-1D Mark IV

05/03/2013 11:07:12 PM · #2

Sure thing.

First, you shouldn't even have bought a UV filter - they're useless unless you're shooting film, or trying to protect your lens from physical damage.

Secondly, what you're seeing is the exact reason you don't want to use filters unless you have to - that's lens flare baby!

You bought a UV filter that isn't multicoated, or coated at all for that matter, which means lots of nasty reflections.

*shrug* You've still got the receipt right? Return it and buy an ND filter or circular polarizer instead.

Canon EF 85mm f/1.2L II USM

05/03/2013 11:13:53 PM · #3

Originally posted by Cory:

Yes I have receipt and also got ND filter. so in other words I should not be using UV filters? or there are some that I can buy? I saw HOYA one at Amazon like this one?

Cory

Canon EOS-1D Mark IV

05/03/2013 11:25:20 PM · #4

Originally posted by pgirish007:

Yes I have receipt and also got ND filter. so in other words I should not be using UV filters? or there are some that I can buy? I saw HOYA one at Amazon like this one?

They have their uses, but blocking UV from your sensor isn't one of them. If you're shooting film, it can be UV sensitive, and can benefit from a UV filter, but our sensors aren't able to even register UV light.

To understand why takes a little bit of physics knowledge, but it's pretty basic. Effectively light exists as wavelengths, only a portion of which is within the visible range.

Notice that UV and IR are outside of the visible range of light. To your DSLR, they're even further out of the range of visible light because a sensor is arranged with a Bayer filter that splits light into three colors (Red,Green,Blue).

Because of this, your sensor is really only able to see red light, blue light, and green light - not discrete wavelengths, but rather those portions of the spectrum, which are sufficient to approximate true color.

So, because of the way DSLR's actually function, there is no way that a UV filter can directly affect image quality.

Interestingly, DSLR's do pick up a little IR, as it's actually red light - but you need to block out all other light, and often remove the filter over the sensor, to actually take these pictures well. If you're interested, look into IR conversion.

Anyway, yeah, totally and completely useless, other than for physical protection, which is arguably also almost never needed.

Cheers, hope this helps.

Message edited by author 2013-05-03 23:25:40.

MAK

Leica CL

Leica 18-56mm f/3.5-5.6 Vario Elmar-T ASPH

05/04/2013 05:03:26 AM · #5

Superb explanation very helpful to me too.. I do not use filters because all they do is cause problems, some would say they protect the front element and I agree, but I do not shoot many hazardous situations.

Tamron SP 24-70mm f/2.8 Di VC USD Canon Mount

05/04/2013 07:50:46 AM · #6

Wow, wonderful details! I thanks Cory! I have been using Camera since 2006 and never had any UV filter on to make sure it is protected. Most of the time I am handling the system and no one else. May be you are right and I will return the filter as I now dont see any usage.

Mike

Canon EOS-5D Mark II

05/04/2013 09:28:30 AM · #7

if you want to protect the front element, get a lens hood.

Tamron SP 24-70mm f/2.8 Di VC USD Canon Mount

05/04/2013 09:44:27 AM · #8

Originally posted by Mike:

if you want to protect the front element, get a lens hood.

I have kept that on no matter what time it is :)

Mike

Canon EOS-5D Mark II

05/05/2013 08:44:53 AM · #9

Originally posted by pgirish007:

Originally posted by Mike:
if you want to protect the front element, get a lens hood.

I have kept that on no matter what time it is :)

I keep it on my 50mm all time to protect the AF of all things.

Spork99

OM System OM-1

Canon EF 100mm f/2.8 USM Macro

05/05/2013 11:43:50 AM · #10

The only good reason to use a UV filter would be to protect the front element in conditions where a lens hood would not, like a sandstorm, at the beach when it's really windy, helicopter LZ...you get the idea.

Modern lens coatings do an excellent job of blocking UV. Filters cause flare. You spent a lot of money on your camera and lenses, why unnecessarily degrade their performance with a cheap piece glass?