To filter or not to filter

"Colin D" wrote in message
...
[SNIP]
In some countries, notably Australia and New Zealand, the preponderance
of UV radiation is much greater than others - ozone hole etc. - and film
shot without a filter can look decidedly blue, despite claims made that
modern lenses are more or less opaque to UV.


I do keep wondering why so many people will say that lenses don't transmit
UV, when everyone from Kodak to Nikon says that they do. And which of us
has never got sunburn through a car window?

Sure optical glass (and adhesives) absorbs some UV, and sure 'modern' lens
designs with lots of elements will absorb more then older designs with
fewer, but they still transmit more than enough to make film overly blue and
distance shots overly hazy when there is a lot of UV about.




Peter

"Colin D" wrote in message
...
[SNIP]
In some countries, notably Australia and New Zealand, the preponderance
of UV radiation is much greater than others - ozone hole etc. - and film
shot without a filter can look decidedly blue, despite claims made that
modern lenses are more or less opaque to UV.


I do keep wondering why so many people will say that lenses don't transmit
UV, when everyone from Kodak to Nikon says that they do. And which of us
has never got sunburn through a car window?

Sure optical glass (and adhesives) absorbs some UV, and sure 'modern' lens
designs with lots of elements will absorb more then older designs with
fewer, but they still transmit more than enough to make film overly blue and
distance shots overly hazy when there is a lot of UV about.




Peter

"Bandicoot" wrote in message
...
"Colin D" wrote in message
...
[SNIP]
In some countries, notably Australia and New Zealand, the preponderance
of UV radiation is much greater than others - ozone hole etc. - and film
shot without a filter can look decidedly blue, despite claims made that
modern lenses are more or less opaque to UV.


I do keep wondering why so many people will say that lenses don't transmit
UV, when everyone from Kodak to Nikon says that they do. And which of us
has never got sunburn through a car window?

Sure optical glass (and adhesives) absorbs some UV, and sure 'modern' lens
designs with lots of elements will absorb more then older designs with
fewer, but they still transmit more than enough to make film overly blue
and
distance shots overly hazy when there is a lot of UV about.



I heard the same story about the SMC Takumar lenses: the combination of the
multicoating and the cement used to bond certain elements together (such as
the 4th and 5th elements on the 50mm f/1.4 SMC Takumar) allegedly absorbed
virtually all UV light.

Photographers wanting to shoot in UV light were advised to use the earlier
Super-Takumar lenses, which were not multicoated (except for a small
percentage that were made with test coatings just before Asahi marketed the
SMC Tak series).

I still use UV filters on all my lenses. And I read recently that TIFFEN,
of all manufacturers, makes a filter that absorbs more UV than anyone
else's. Apparently most UV filters let a significant amount of UV light
pass.

Unfortunately, I cannot remember which Tiffin filter won the UV absorption
test. Perhaps someone here knows and can tell us.

"Bandicoot" wrote in message
...
"Colin D" wrote in message
...
[SNIP]
In some countries, notably Australia and New Zealand, the preponderance
of UV radiation is much greater than others - ozone hole etc. - and film
shot without a filter can look decidedly blue, despite claims made that
modern lenses are more or less opaque to UV.


I do keep wondering why so many people will say that lenses don't transmit
UV, when everyone from Kodak to Nikon says that they do. And which of us
has never got sunburn through a car window?

Sure optical glass (and adhesives) absorbs some UV, and sure 'modern' lens
designs with lots of elements will absorb more then older designs with
fewer, but they still transmit more than enough to make film overly blue
and
distance shots overly hazy when there is a lot of UV about.



I heard the same story about the SMC Takumar lenses: the combination of the
multicoating and the cement used to bond certain elements together (such as
the 4th and 5th elements on the 50mm f/1.4 SMC Takumar) allegedly absorbed
virtually all UV light.

Photographers wanting to shoot in UV light were advised to use the earlier
Super-Takumar lenses, which were not multicoated (except for a small
percentage that were made with test coatings just before Asahi marketed the
SMC Tak series).

I still use UV filters on all my lenses. And I read recently that TIFFEN,
of all manufacturers, makes a filter that absorbs more UV than anyone
else's. Apparently most UV filters let a significant amount of UV light
pass.

Unfortunately, I cannot remember which Tiffin filter won the UV absorption
test. Perhaps someone here knows and can tell us.

On Wed, 8 Sep 2004 17:22:40 +0100, "Bandicoot"
wrote:

I do keep wondering why so many people will say that lenses don't transmit
UV, when everyone from Kodak to Nikon says that they do. And which of us
has never got sunburn through a car window?

In order to harm a photo, not only must the UV light get through, but
the film or sensor must have a sufficient response to it.

It's also important to note that the term UV covers a range of
wavelengths, each of which interacts with different materials
differently. For example, a "driving sunburn" is likely to be caused
by light in the UV-B range (280-315nm). Film is more likely to be
sensitive to light in the UV-A range (315-400nm).

Cheap UV filters may not offer much filtering at all, as seen he
http://www.photo.net/equipment/filters/

Even with the best UV filter you should do a cost-benefit analysis.
Given your film or sensor, is the benefit of blocking UV worth the
risk of adding two more glass-air surfaces?

Myself, I use UV filters mainly for lens protection. In most benign
shooting environment, I take them off. Naturally, there's an
exception. When I'm using an undiffused flash (say, through a
snoot) and I don't want to use a warming or soft-focus filter, I'll
use a UV just in case.

--
Michael Benveniste --
Spam and UCE professionally evaluated for $419. Use this email
address only to submit mail for evaluation.

Michael Benveniste wrote:
Film is more likely to be
sensitive to light in the UV-A range (315-400nm).

According to my (1935 ed.,I think) Ilford Manual of Photography
(ed. Geroge E. Brown):

"An ordinary photographic plate will readily respond to
ultra-violet radiation between 4000 Angstroms and 2300
Angstroms." (p.104)

2300 Angstroms is the same as 230nm.

The main reason why spectral plots of film response don't
usually show this extended range is that most of the
equipment used contains glass which absorbs UV radiation.
Some films, especially modern colour films, may have a
UV absorbing layer, but I believe that most B&W films have
no such filtering.

In my copy of the Asahi Pentax Manual by Joseph D. Cooper
(1975) there is a datasheet on the UA Takumar 85mm f/4.5
which is claimed to be corrected for wavelengths as short
as 220nm. It uses quartz and fluorite elements and contains
no glass.


Cheap UV filters may not offer much filtering at all, as seen he
http://www.photo.net/equipment/filters/

Actually it shows that some expensive UV filters have
little UV filtering ability. The Tiffen Haze-1, which
scored best in that test, is not an expensive filter.

Even with the best UV filter you should do a cost-benefit analysis.
Given your film or sensor, is the benefit of blocking UV worth the
risk of adding two more glass-air surfaces?

The risk is a lot smaller than some advertisments for
expensive filters would have you believe, even if the
filter is uncoated. If you actually need to remove UV,
than you should use an effective UV filter such as the
Tiffen UV Haze-1. If you are doing photography at
high altitudes, a real UV filter may be a good idea.

Peter.
--

Michael Benveniste wrote:
Film is more likely to be
sensitive to light in the UV-A range (315-400nm).

According to my (1935 ed.,I think) Ilford Manual of Photography
(ed. Geroge E. Brown):

"An ordinary photographic plate will readily respond to
ultra-violet radiation between 4000 Angstroms and 2300
Angstroms." (p.104)

2300 Angstroms is the same as 230nm.

The main reason why spectral plots of film response don't
usually show this extended range is that most of the
equipment used contains glass which absorbs UV radiation.
Some films, especially modern colour films, may have a
UV absorbing layer, but I believe that most B&W films have
no such filtering.

In my copy of the Asahi Pentax Manual by Joseph D. Cooper
(1975) there is a datasheet on the UA Takumar 85mm f/4.5
which is claimed to be corrected for wavelengths as short
as 220nm. It uses quartz and fluorite elements and contains
no glass.


Cheap UV filters may not offer much filtering at all, as seen he
http://www.photo.net/equipment/filters/

Actually it shows that some expensive UV filters have
little UV filtering ability. The Tiffen Haze-1, which
scored best in that test, is not an expensive filter.

Even with the best UV filter you should do a cost-benefit analysis.
Given your film or sensor, is the benefit of blocking UV worth the
risk of adding two more glass-air surfaces?

The risk is a lot smaller than some advertisments for
expensive filters would have you believe, even if the
filter is uncoated. If you actually need to remove UV,
than you should use an effective UV filter such as the
Tiffen UV Haze-1. If you are doing photography at
high altitudes, a real UV filter may be a good idea.

Peter.
--

Michael Benveniste wrote:
Film is more likely to be
sensitive to light in the UV-A range (315-400nm).

According to my (1935 ed.,I think) Ilford Manual of Photography
(ed. Geroge E. Brown):

"An ordinary photographic plate will readily respond to
ultra-violet radiation between 4000 Angstroms and 2300
Angstroms." (p.104)

2300 Angstroms is the same as 230nm.

The main reason why spectral plots of film response don't
usually show this extended range is that most of the
equipment used contains glass which absorbs UV radiation.
Some films, especially modern colour films, may have a
UV absorbing layer, but I believe that most B&W films have
no such filtering.

In my copy of the Asahi Pentax Manual by Joseph D. Cooper
(1975) there is a datasheet on the UA Takumar 85mm f/4.5
which is claimed to be corrected for wavelengths as short
as 220nm. It uses quartz and fluorite elements and contains
no glass.


Cheap UV filters may not offer much filtering at all, as seen he
http://www.photo.net/equipment/filters/

Actually it shows that some expensive UV filters have
little UV filtering ability. The Tiffen Haze-1, which
scored best in that test, is not an expensive filter.

Even with the best UV filter you should do a cost-benefit analysis.
Given your film or sensor, is the benefit of blocking UV worth the
risk of adding two more glass-air surfaces?

The risk is a lot smaller than some advertisments for
expensive filters would have you believe, even if the
filter is uncoated. If you actually need to remove UV,
than you should use an effective UV filter such as the
Tiffen UV Haze-1. If you are doing photography at
high altitudes, a real UV filter may be a good idea.

Peter.
--

Peter Irwin writes:

Michael Benveniste wrote:
Film is more likely to be
sensitive to light in the UV-A range (315-400nm).

According to my (1935 ed.,I think) Ilford Manual of Photography
(ed. Geroge E. Brown):

"An ordinary photographic plate will readily respond to
ultra-violet radiation between 4000 Angstroms and 2300
Angstroms." (p.104)

Note well that colour response curves are generally far far narrower
than those for the various BW films.

B