UV or Skylight ?

koukon · 01-22-2012, 01:34 PM

Hey everyone!!
I'd like to have some suggestions about the "always-on-lens" filter.Is a skylight better than a UV?Is a skylight an "allweather" filter?I mean is it good on a sunny day or on a cloudy?

Thanks in advance!!!

SpecialK · 01-22-2012, 01:48 PM

Digital sensors are not affected by UV. A skylight filter warms the light balance slightly.

If you are going to spend money on an unneeded filter, at least buy a good one.

Philoslothical · 01-22-2012, 01:49 PM

Neither, unless you're shooting in very dusty or sandy areas, or at a high risk of something (kids or pets, for instance) hitting the front element of your lens.

Which lens is this for? Some people employ the strategy that it's much cheaper to replace an $80 filter than a $1000 lens, which may hold some weight. It doesn't make sense for inexpensive lenses though, as any extra glass like that can only degrade image quality. Cheaper filters are worse, of course.

Also beware shooting at or near light sources with any kind of filter on. It can cause flaring and ghosting that can ruin a shot.

koukon · 01-22-2012, 02:08 PM

Thanks guys..I'm wondering to buy a skylight(I found a hoya hmc sky at amazon at 18euros) to protect my lens and do exactly that SpecialK said..to warm the light balance..or better buy a CP????I'm confused...

**jatrax** · 01-22-2012, 02:22 PM

Filters were very important on film as it was about the only way to correct white balance and get the color right. With digital they are not particularly useful. The only exception to this is a circular polarizer which cannot be duplicated in software very well.

If you are trying to change the color or white balance of an image it is much easier to do that on the computer in post processing.

In my opinion buying a filter "to protect the lens" is a waste of money and is one of those things sales staff are trained to sell you because the profit margin is high. If you are shooting in the desert with blowing sand hitting the lens, OK maybe. Otherwise buy a good hood, the hood will protect the lens just as well and actually improve the image by cutting flare.

As noted above if you are using $1,000 lenses in bad environments OK maybe the cost of a filter is worth it. But anything you put in front of your lens will degrade the image quality and filters especially are prone to flare and ghosting as already noted.

SpecialK · 01-22-2012, 03:11 PM

Originally posted by koukon

Thanks guys..I'm wondering to buy a skylight(I found a hoya hmc sky at amazon at 18euros) to protect my lens and do exactly that SpecialK said..to warm the light balance..or better buy a CP????I'm confused...

The AWB of the camera will negate the warming influence of the skylight. A CPL nicely cuts reflections and saturates color, but tends to make the sky unnaturally dark. No filters here...

Anvh · 01-22-2012, 03:21 PM

Originally posted by Philoslothical

at a high risk of something (kids or pets, for instance) hitting the front element of your lens.

Yeah a kid hitting your lens will ruin it for good

Philoslothical · 01-22-2012, 04:16 PM

Ha. I was thinking more about greasy fingerprints, and those times you go to take a closeup of the cat, who decides it's really important to taste the lens.

VisualDarkness · 01-22-2012, 05:02 PM

Skylight east away quite some light. The only UV-test you'll ever need: UV filters test - Introduction - Lenstip.com
I personally should use filters on every lens due to my clumsiness but I'm trying to ween off that habit.

RioRico · 01-22-2012, 05:29 PM

If you're shooting amidst gusting salt-spray and sand or spraying mud/blood/beer, then clear optical glass can protect the objective. You get better physical protection with a good lens hood. What a UV or skylight or other such 'protects' is the seller's cashflow, not the lens. By hoods, not skylights.

Marc Sabatella · 01-23-2012, 10:58 AM

Both filters degrade your image the exact same amount, and neither gives it much protection at all from the most likely things that might damage a lens (eg, dropping it). If you want to degrade the image quality without providing much protection, I can do that for you more easily - just put the greasy fingerprint on directly on your lens.

VisualDarkness · 01-23-2012, 11:25 AM

Originally posted by Marc Sabatella

Both filters degrade your image the exact same amount, and neither gives it much protection at all from the most likely things that might damage a lens (eg, dropping it). If you want to degrade the image quality without providing much protection, I can do that for you more easily - just put the greasy fingerprint on directly on your lens.

Is that really true? Optimal UV-filters cut out light that you wouldn't even have been able to see while skylight takes light from the visible part of the spectrum therefor lowers the usable light hitting the sensor. At least this is my theory.

Marc Sabatella · 01-23-2012, 11:41 AM

OK, you're probably right about there being a difference. But most of the degradation is from increased flare and general softness and/or chromatic aberration, not from any reduction in light.

BTW, my comment about the fingerprint was meant facetiously of course, but with an element of truth - the only thing the filter really protects you from is something that wouldn't have degraded image quality much more than the filter itself does. And of course, fingerprints are easily cleaned, and wouldn't happen very often if you used a hood, which actually protects the lens far better than a filter while actually *improving* image quality. But then, this is a very old debate, with probably thousands of posts on the topic already under the bridge.

**gofour3** · 01-23-2012, 12:48 PM

Skylight filters were used mainly with colour slide film, not sure what use they would have on digital.

Phil.

Philoslothical · 01-23-2012, 03:34 PM

Originally posted by SpecialK

The AWB of the camera will negate the warming influence of the skylight.

This should be enough to settle the question right here. It's true, you're artificially changing the WB with the filter, and then artificially "correcting" that change in the camera software. It's two unnecessary steps that can't help the end result any. You can tweak WB in-camera, or preferably in post, but anything that the camera isn't aware of, like a filter, it will fight against while trying to properly expose the shot.

01-22-2012, 01:34 PM	#1
koukon Forum Member Join Date: Nov 2011 Photos: Gallery Posts: 51	UV or Skylight ? Hey everyone!! I'd like to have some suggestions about the "always-on-lens" filter.Is a skylight better than a UV?Is a skylight an "allweather" filter?I mean is it good on a sunny day or on a cloudy? Thanks in advance!!!

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01-22-2012, 01:48 PM	#2
SpecialK Pentaxian Join Date: Dec 2006 Location: So California Photos: Gallery Posts: 16,481	Digital sensors are not affected by UV. A skylight filter warms the light balance slightly. If you are going to spend money on an unneeded filter, at least buy a good one.

01-22-2012, 01:49 PM	#3
Philoslothical Veteran Member Join Date: May 2011 Posts: 1,889	Neither, unless you're shooting in very dusty or sandy areas, or at a high risk of something (kids or pets, for instance) hitting the front element of your lens. Which lens is this for? Some people employ the strategy that it's much cheaper to replace an $80 filter than a $1000 lens, which may hold some weight. It doesn't make sense for inexpensive lenses though, as any extra glass like that can only degrade image quality. Cheaper filters are worse, of course. Also beware shooting at or near light sources with any kind of filter on. It can cause flaring and ghosting that can ruin a shot.

01-22-2012, 02:08 PM	#4
koukon Forum Member Join Date: Nov 2011 Photos: Gallery Posts: 51 Original Poster	Thanks guys..I'm wondering to buy a skylight(I found a hoya hmc sky at amazon at 18euros) to protect my lens and do exactly that SpecialK said..to warm the light balance..or better buy a CP????I'm confused...

01-22-2012, 02:22 PM	#5
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Filters were very important on film as it was about the only way to correct white balance and get the color right. With digital they are not particularly useful. The only exception to this is a circular polarizer which cannot be duplicated in software very well. If you are trying to change the color or white balance of an image it is much easier to do that on the computer in post processing. In my opinion buying a filter "to protect the lens" is a waste of money and is one of those things sales staff are trained to sell you because the profit margin is high. If you are shooting in the desert with blowing sand hitting the lens, OK maybe. Otherwise buy a good hood, the hood will protect the lens just as well and actually improve the image by cutting flare. As noted above if you are using $1,000 lenses in bad environments OK maybe the cost of a filter is worth it. But anything you put in front of your lens will degrade the image quality and filters especially are prone to flare and ghosting as already noted.

01-22-2012, 03:11 PM	#6
SpecialK Pentaxian Join Date: Dec 2006 Location: So California Photos: Gallery Posts: 16,481	Originally posted by koukon Thanks guys..I'm wondering to buy a skylight(I found a hoya hmc sky at amazon at 18euros) to protect my lens and do exactly that SpecialK said..to warm the light balance..or better buy a CP????I'm confused... The AWB of the camera will negate the warming influence of the skylight. A CPL nicely cuts reflections and saturates color, but tends to make the sky unnaturally dark. No filters here...

01-22-2012, 03:21 PM	#7
Anvh Veteran Member Join Date: Sep 2011 Posts: 4,616	Originally posted by Philoslothical at a high risk of something (kids or pets, for instance) hitting the front element of your lens. Yeah a kid hitting your lens will ruin it for good

01-22-2012, 04:16 PM	#8
Philoslothical Veteran Member Join Date: May 2011 Posts: 1,889	Ha. I was thinking more about greasy fingerprints, and those times you go to take a closeup of the cat, who decides it's really important to taste the lens.

01-22-2012, 05:02 PM	#9
VisualDarkness Veteran Member Join Date: Nov 2011 Location: Uppsala, Sweden Photos: Gallery Posts: 4,439	Skylight east away quite some light. The only UV-test you'll ever need: UV filters test - Introduction - Lenstip.com I personally should use filters on every lens due to my clumsiness but I'm trying to ween off that habit.

01-22-2012, 05:29 PM	#10
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	If you're shooting amidst gusting salt-spray and sand or spraying mud/blood/beer, then clear optical glass can protect the objective. You get better physical protection with a good lens hood. What a UV or skylight or other such 'protects' is the seller's cashflow, not the lens. By hoods, not skylights.

01-23-2012, 10:58 AM	#11
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Both filters degrade your image the exact same amount, and neither gives it much protection at all from the most likely things that might damage a lens (eg, dropping it). If you want to degrade the image quality without providing much protection, I can do that for you more easily - just put the greasy fingerprint on directly on your lens.

01-23-2012, 11:25 AM	#12
VisualDarkness Veteran Member Join Date: Nov 2011 Location: Uppsala, Sweden Photos: Gallery Posts: 4,439	Originally posted by Marc Sabatella Both filters degrade your image the exact same amount, and neither gives it much protection at all from the most likely things that might damage a lens (eg, dropping it). If you want to degrade the image quality without providing much protection, I can do that for you more easily - just put the greasy fingerprint on directly on your lens. Is that really true? Optimal UV-filters cut out light that you wouldn't even have been able to see while skylight takes light from the visible part of the spectrum therefor lowers the usable light hitting the sensor. At least this is my theory.

01-23-2012, 11:41 AM	#13
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	OK, you're probably right about there being a difference. But most of the degradation is from increased flare and general softness and/or chromatic aberration, not from any reduction in light. BTW, my comment about the fingerprint was meant facetiously of course, but with an element of truth - the only thing the filter really protects you from is something that wouldn't have degraded image quality much more than the filter itself does. And of course, fingerprints are easily cleaned, and wouldn't happen very often if you used a hood, which actually protects the lens far better than a filter while actually improving image quality. But then, this is a very old debate, with probably thousands of posts on the topic already under the bridge.

01-23-2012, 12:48 PM	#14
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 8,091	Skylight filters were used mainly with colour slide film, not sure what use they would have on digital. Phil.

01-23-2012, 03:34 PM	#15
Philoslothical Veteran Member Join Date: May 2011 Posts: 1,889	Originally posted by SpecialK The AWB of the camera will negate the warming influence of the skylight. This should be enough to settle the question right here. It's true, you're artificially changing the WB with the filter, and then artificially "correcting" that change in the camera software. It's two unnecessary steps that can't help the end result any. You can tweak WB in-camera, or preferably in post, but anything that the camera isn't aware of, like a filter, it will fight against while trying to properly expose the shot.