skylight/UV filters
Posted 28/03/2006 - 18:12
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Absolutely no idea.....but I'd be interested to find out
Die my dear doctor, that's the last thing I shall do!
Posted 28/03/2006 - 18:57
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I was surprised by the results.
I tested three filters I have around here.
The first is a Hoya Skylight 1A
CIE L*,a*,b*: 97.29, 1.70, 0.63
Damping: 6.85%
Transmision UV380: 14,65%
Transmission UV400: 19,32%
The second is a Hama Skylight 1A
CIE L*,a*,b*: 96.30, 1.37, 0.79
Damping: 9.27%
Transmision UV380: 9,82%
Transmission UV400: 14,71%
The third is a Vanguard UV filter. It only mentions UV on the filter
CIE L*,a*,b*: 96.73, -0,61, 0.15
Damping: 8.24%
Transmision UV380: 34.28%
Transmission UV400: 37.90%
The CIE L*a*b* values are measured with a D65 lightsource and 2 degree observer. The filters were measured with a Tec5 TFM Lens Colour Analyser .
As a side note to the UV transmission values, I allso measured the lenses from a pair of sunglasses with a UV filter and these glasses have a UV transmission of 0.05% for both UV380 and 400.
The cheap vanguard filter doesn't really filter much UV light. It is however the most neutral in colour.
You see about 5% difference in transmission values between the two Skylight 1A filters. I would be interested in what a Skylight 1A filter ideally should do.
I tested three filters I have around here.
The first is a Hoya Skylight 1A
CIE L*,a*,b*: 97.29, 1.70, 0.63
Damping: 6.85%
Transmision UV380: 14,65%
Transmission UV400: 19,32%
The second is a Hama Skylight 1A
CIE L*,a*,b*: 96.30, 1.37, 0.79
Damping: 9.27%
Transmision UV380: 9,82%
Transmission UV400: 14,71%
The third is a Vanguard UV filter. It only mentions UV on the filter
CIE L*,a*,b*: 96.73, -0,61, 0.15
Damping: 8.24%
Transmision UV380: 34.28%
Transmission UV400: 37.90%
The CIE L*a*b* values are measured with a D65 lightsource and 2 degree observer. The filters were measured with a Tec5 TFM Lens Colour Analyser .
As a side note to the UV transmission values, I allso measured the lenses from a pair of sunglasses with a UV filter and these glasses have a UV transmission of 0.05% for both UV380 and 400.
The cheap vanguard filter doesn't really filter much UV light. It is however the most neutral in colour.
You see about 5% difference in transmission values between the two Skylight 1A filters. I would be interested in what a Skylight 1A filter ideally should do.
Camera:K20D|Ist*DS|Spotmatic II|MZ-10
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Posted 28/03/2006 - 23:16
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The UV filter only filters UV light, has no effect on exposure and is used to protect the lens and to reduce the blue cast at high altitudes. It also cuts through haze to some extent.
The Skylight 1A filters more strongly, and ever so slightly warms the pciture.
The Skylight 1B is stronger still and might just need a whisker more exposure.
The 81A filter definitely warms the picture and needs some extra exposure, maybe 1/3 to 1/2 a stop. Then there are 81B, 81C, etc. filters.
These filters warm up cloudy days, remove blue casts in shadows, and indeed are sometimes called "Cloudy" filters.
Hope that helps a bit, although it is not as technically precise as your fugures!
The Skylight 1A filters more strongly, and ever so slightly warms the pciture.
The Skylight 1B is stronger still and might just need a whisker more exposure.
The 81A filter definitely warms the picture and needs some extra exposure, maybe 1/3 to 1/2 a stop. Then there are 81B, 81C, etc. filters.
These filters warm up cloudy days, remove blue casts in shadows, and indeed are sometimes called "Cloudy" filters.
Hope that helps a bit, although it is not as technically precise as your fugures!
Best regards, John
Posted 29/03/2006 - 05:57
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CIELAB (CIE L* a* b*, CIE Lab): A mathematical derivative of CIE XYZ (1931) that describes colors using three synthetic primaries: L* (which indicates Lightness), a* (which indicates red-greenness), and b* (which indicates yellow-blueness).
hmm, so the Hoya delivers a slightly lighter image, with more red-greenness but less yellow-blueness than the Hama.
It also lets through more UV - approx. 17% overall, as opposed to the Hama's 12%.
Both Skylights are more effective UV-blockers than the Vanguard which lets through approx. 35%.
The Vanguard however has the least effect on the colour characteristics.
Lightness is midway between the Skylights and it slightly blocks red-greenness and very slightly enhances the yellow-blueness.
My conclusion - assuming I'm interpreting the figures correctly, is:
the Hoya has a slightly stronger 'warming' effect than the Hama but is slightly less effective at cutting through haze etc.
The Vanguard provides the most natural colour balance but is the least effective filter of UV light.
You have a darned good pair of sunglasses!
hmm, so the Hoya delivers a slightly lighter image, with more red-greenness but less yellow-blueness than the Hama.
It also lets through more UV - approx. 17% overall, as opposed to the Hama's 12%.
Both Skylights are more effective UV-blockers than the Vanguard which lets through approx. 35%.
The Vanguard however has the least effect on the colour characteristics.
Lightness is midway between the Skylights and it slightly blocks red-greenness and very slightly enhances the yellow-blueness.
My conclusion - assuming I'm interpreting the figures correctly, is:
the Hoya has a slightly stronger 'warming' effect than the Hama but is slightly less effective at cutting through haze etc.
The Vanguard provides the most natural colour balance but is the least effective filter of UV light.
You have a darned good pair of sunglasses!
Die my dear doctor, that's the last thing I shall do!
Posted 29/03/2006 - 14:03
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BTW any glass should reduce uv i believe lead used in the molding, cooling process acts as a filter, good enough in fact that farmers once switched from glass to plexi windows on chicken coups to improve animal health.
your pentax glass with multi coating should be all the uv protection you need and any uv filter put in front isn't likely to make any noticable improvement. cheap uncoated lenses may be a different matter, I wouldn't know. but i do know that anything you put in front of your lens could adversely affect image quality.
I could be wrong...still on first cup-o-joe.
I'm not big on using filters in general. Have had expensive glass in the arctic, to dessert like conditions to swamps and can honestly attest that with proper care you'll rarely need a uv filter for protection if ever.
don't drop your camera is the short answer.
your pentax glass with multi coating should be all the uv protection you need and any uv filter put in front isn't likely to make any noticable improvement. cheap uncoated lenses may be a different matter, I wouldn't know. but i do know that anything you put in front of your lens could adversely affect image quality.
I could be wrong...still on first cup-o-joe.
I'm not big on using filters in general. Have had expensive glass in the arctic, to dessert like conditions to swamps and can honestly attest that with proper care you'll rarely need a uv filter for protection if ever.
don't drop your camera is the short answer.
Fired many shots. Didn't kill anything.
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1130 posts
19 years
Netherlands
Does anyone have a idea on how much of the UV light should be filtered out and how much of the overall light should go through at minimum?
(I am just curious what the anwsers are, I will give some actual measurement data from a quick test I did yesterday evening when I get back with the paper with the data.)
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T