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UV Filter: % light reflection?



 
 
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  #1  
Old February 9th 05, 03:43 PM
Joseph Meehan
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Default 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  
Old February 9th 05, 04:03 PM
David J. Littleboy
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Default


"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  
Old February 9th 05, 04:10 PM
YoYo
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Default

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  
Old February 9th 05, 04:17 PM
Bob Salomon
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Posts: n/a
Default

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  
Old February 9th 05, 04:20 PM
Bob Salomon
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Default

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  
Old February 9th 05, 04:26 PM
Don Stauffer in Minneapolis
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Default

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  
Old February 9th 05, 04:29 PM
Jeremy
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Posts: n/a
Default


"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  
Old February 9th 05, 04:32 PM
David J. Littleboy
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Default


"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  
Old February 9th 05, 09:48 PM
Pete D
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Default



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  
Old February 9th 05, 09:57 PM
Bob Salomon
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Default

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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