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#1
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UV Filter: % light reflection?
photon wrote:
Hello, I have a new Nikon D70 with the kit lens (18-70 f/3.5-4.5). Upon buying the camera I immediately slapped a UV filter on the front of the lens to protect it. Time out for my editorial comments: After a number of years in professional photography where I used many "damaged" lenses with chips and scratches and years of photo retail work where the profit from selling a filter or a case, may well be more than that on the camera itself, I know that those scratches and chips that so many people fear do little or nothing to the function of the lens. I also know that retailers have been pushing UV filters for years as a way of making more profit and fear is a great sales technique. We now have a generation or two of photographers who have an unreasonable fear of lens damage. However, I have recently learned about the reflection properties of non-coated glass, and that my Promaster UV filter might not only be mostly ignoring UV (1) but might actually reflect up to 7% (2) of light away from my Nikon lens! 7% is the difference between a f2.0 and a f2.4 about 1/14 of a stop. You can't see that. In addition anything you do, other than removing it, is going to still have some reflection and the glass will absorb a little so you might be able to gain 1/30 of a stop. I doubt if that is worth worrying about. In addition, I believe I have taken shots with additional reflected sun flare spots, but, I haven't tried taking a double with filter/without filter set to look for the glare. This is where you may see the difference and the difference between a good filter (B+W) and a cheap filter will be noticeable if you look for it. However you will still have the filter sitting out there right where it can cause flare not matter how good it may be. Take it of and you will have removed all of the filter induced flare along with any optical errors that filter may have. Add a good lens shade (one designed for your specific lens, and you will reduce flare even more with or without the filter. That filter will also help protect your lens from most damage. The only time I recommend using a filter to "protect" as lens are those few time where something like blowing sand, or some sort of nasty stuff in the air as I have found on many industrial sites. So, I have started looking at higher quality HOYA and B+W filters. How important is it to have a coated vs uncoated UV filter for lens protection? Am I really reflecting that much light or damaging image quality that much? I would not buy a filter that was not coated. Thanks John (1) http://www.photo.net/equipment/filters/ (2) http://kenrockwell.com/tech/lenstech.htm -- Joseph Meehan 26 + 6 = 1 It's Irish Math |
#2
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"Joseph Meehan" wrote: Time out for my editorial comments: After a number of years in professional photography where I used many "damaged" lenses with chips and scratches and years of photo retail work where the profit from selling a filter or a case, may well be more than that on the camera itself, I know that those scratches and chips that so many people fear do little or nothing to the function of the lens. I also know that retailers have been pushing UV filters for years as a way of making more profit and fear is a great sales technique. We now have a generation or two of photographers who have an unreasonable fear of lens damage. Here's my take on it: I'm _incredibly_ careful of an unprotected lens. The lens cap stays on until I see a shot, and goes back on after the shot. As a result, my unprotected lenses are clean. Very clean. But a UV filter doesn't need that amount of care. As a result, my UV filters are filthy. So to answer the original question, in real-life practice, UV filters cut out a lot of light and degrade the image horribly. David J. Littleboy Tokyo, Japan |
#3
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I agree with Joseph Meehan, but photon you have a DSLR do some
test shots of your own and compare (not like it cost anything other then time and battery drain). Learn & Use what you paid for. "photon" wrote in message ... Hello, I have a new Nikon D70 with the kit lens (18-70 f/3.5-4.5). Upon buying the camera I immediately slapped a UV filter on the front of the lens to protect it. However, I have recently learned about the reflection properties of non-coated glass, and that my Promaster UV filter might not only be mostly ignoring UV (1) but might actually reflect up to 7% (2) of light away from my Nikon lens! In addition, I believe I have taken shots with additional reflected sun flare spots, but, I haven't tried taking a double with filter/without filter set to look for the glare. So, I have started looking at higher quality HOYA and B+W filters. How important is it to have a coated vs uncoated UV filter for lens protection? Am I really reflecting that much light or damaging image quality that much? Thanks John (1) http://www.photo.net/equipment/filters/ (2) http://kenrockwell.com/tech/lenstech.htm |
#4
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In article ,
photon wrote: Hello, I have a new Nikon D70 with the kit lens (18-70 f/3.5-4.5). Upon buying the camera I immediately slapped a UV filter on the front of the lens to protect it. However, I have recently learned about the reflection properties of non-coated glass, and that my Promaster UV filter might not only be mostly ignoring UV (1) but might actually reflect up to 7% (2) of light away from my Nikon lens! In addition, I believe I have taken shots with additional reflected sun flare spots, but, I haven't tried taking a double with filter/without filter set to look for the glare. So, I have started looking at higher quality HOYA and B+W filters. How important is it to have a coated vs uncoated UV filter for lens protection? Am I really reflecting that much light or damaging image quality that much? Thanks John (1) http://www.photo.net/equipment/filters/ (2) http://kenrockwell.com/tech/lenstech.htm As an example a standard coated Heliopan filter that is coated on both sides, naturally, will reflect about 4% of the light at each air to glass surface. A SH-PMC 16 layer Heliopan multi coated filter (8 layers per side) reduces the reflection to about 0.05% at each glass to air surface. In addition the top layer on each side repels moisture and dust making them very easy to keep clean. -- To reply no_ HPMarketing Corp. |
#5
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In article ,
"David J. Littleboy" wrote: UV filters cut out a lot of light and degrade the image horribly. But that is because in your previous paragraph you state that your "UV filters are filthy" That helps to explain your conclusion above. I can tell you from experience that we have sold Heliopan UV filters to NASA for Space Shuttle and Space Station photography and their shots show no degradation from using a filter. -- To reply no_ HPMarketing Corp. |
#6
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There are two problems with reflection from lens elements and filters.
First, you do loose some energy. However, with uncoated glass the amount is negligible. 7% is a small fraction of one stop. More important is the re-reflection of light from interior elements. Say some light bounces off front surface of objective lens. It hits filter, and 7% of that is bounced back INTO camera. Ghost images and flare result from such reflections. In a high contrast scene these false images and veiling glare can be objectionable. That is why AR coated lenses and filters are highly desirable. Even if your objective has well coated elements, the filter has two surfaces. So incident light can bounce off of REAR surface of element, get reflected back by front surface, and enter camera to make a ghost image. So filters should be AR coated. photon wrote: Hello, I have a new Nikon D70 with the kit lens (18-70 f/3.5-4.5). Upon buying the camera I immediately slapped a UV filter on the front of the lens to protect it. However, I have recently learned about the reflection properties of non-coated glass, and that my Promaster UV filter might not only be mostly ignoring UV (1) but might actually reflect up to 7% (2) of light away from my Nikon lens! In addition, I believe I have taken shots with additional reflected sun flare spots, but, I haven't tried taking a double with filter/without filter set to look for the glare. So, I have started looking at higher quality HOYA and B+W filters. How important is it to have a coated vs uncoated UV filter for lens protection? Am I really reflecting that much light or damaging image quality that much? Thanks John (1) http://www.photo.net/equipment/filters/ (2) http://kenrockwell.com/tech/lenstech.htm |
#7
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"photon" wrote in message ... How important is it to have a coated vs uncoated UV filter for lens protection? Am I really reflecting that much light or damaging image quality that much? Erwin Puts, on the Leica website, assesses filters as contributing 2% to image degradation for a really good filter, to as high as 10% image degradation for a cheap filter (this is not just reflections, it has to do with quality of glass, whether properly polished, etc.). I always use UV filters, because I am shooting older lenses, that I cannot easily replace if damaged. I am also one of those lens-cleaning obsessed people, and I would prefer to sacrifice a filter, rather than leave cleaning marks on my front elements. I really don't much care about the additional cost of a filter, even though I understand that dealers push them as high-profit items. So, to respond to your question, it really is a matter of judgment. I personally have never seen any image degradation resulting from filters, but I HAVE seen many times where a filter took the hit instead of the lens when it came to smudges, dust, etc. And that, to me, is more important than losing 2% of the image quality. Your mileage may vary . . . |
#8
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"Bob Salomon" wrote: "David J. Littleboy" wrote: UV filters cut out a lot of light and degrade the image horribly. But that is because in your previous paragraph you state that your "UV filters are filthy" Of course. That was why I said "in real life practice". You snipped the most important part. That helps to explain your conclusion above. Sheesh. It's not about "helping to explain", it's the whole point. In real life, UV filters are an optical disaster. (I suppuse if someone were infinitely anal and kept a lens cap on the UV filter, then the filter would be clean. For US$600, I can keep a lens cap on, but for US$15, most people can't. So UV filters are foul.) I can tell you from experience that we have sold Heliopan UV filters to NASA for Space Shuttle and Space Station photography and their shots show no degradation from using a filter. There's a lot less gunk in space than there is down here, and a lot more UV to filter out. David J. Littleboy Tokyo, Japan |
#9
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I can tell you from experience that we have sold Heliopan UV filters to NASA for Space Shuttle and Space Station photography and their shots show no degradation from using a filter. Also, just because someone at NASA thinks it is a good idea does not make it the right thing to do. |
#10
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In article ,
"Pete D" wrote: does not make it the right thing to do. Doesn't make it wrong either. however no one on this NG has anywhere near the expense of re-shooting in case of problems that NASA has. -- To reply no_ HPMarketing Corp. |
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