>news:3e388e95.45396080@newsstand.cit.cornell.edu...

>> On Thu, 30 Jan 2003 01:48:31 -0000, "Bandicoot"

>> <"insert_handle_here"@techemail.com> wrote:

>> >"Neuman - Ruether" <d_ruether@hotmail.com> wrote in message

>> >news:3e3eef3e.4599231@newsstand.cit.cornell.edu...

>>

>> >[SNIP]

>>

>> >> I feel like I'm running around, sticking fingers

>> >> in leaks, only to have to leave, and plug yet

>> >> another...! ;-) OK: UV filters will have NO effect

>> >> on the image shot with most multi-element lenses

>> >> (and it cannot "cut through haze" - only a severe

>> >> restriction of filter light transmission to the

>> >> red-IR end of the spectrum, with suitable

>> >> IR-sensitive film used, can do this); a skylight

>> >> (or even a medium yellow filter) will have VERY

>> >> LITTLE (as in, "mostly useless") effect on tones

>> >> under most circumstances in B&W photography

>> >> (though a skylight can offset some bluishness with

>> >> color *slides*, but not negatives); filters can

>> >> serve well for lens front-element protection (a

>> >> shade also helps, and is *sometimes* necessary);

>> >> a good filter need not be multicoated, though

>> >> single-coating can be useful (and it is easier to

>> >> clean than MC filters); expensive brands of filters

>> >> offer little advantage over good medium-priced

>> >> filters (I like Hoya single-coated for this, and

>> >> dislike Tiffen); a good filter has NO VISIBLE

>> >> EFFECT on image sharpness with wide-angles and

>> >> teles, let alone normal FL lenses, *even with

>> >> critical observation*. All this is regardless of

>> >> the filter-manufacturers' sales-lit "examples"

>> >> or myths propagated here, and is arrived at

>> >> through "real-world" tests done by me... I

>> >> encourage anyone to do your own tests, being

>> >> as careful as possible to reduce irrelevant

>> >> variables, to verify the above for yourself...

>> >> David Ruether

>>

>> >I was intrigued by this argument so I went off looking for some

>transmission

>> >charts for filters. I found one from Pentax, and I'm assuming other

>> >manufacturers of high quality filters will have more or less comparable

>> >curves for their lines of filters. I've put a copy of this chart at:

>> >

>> >http://www.bard-hill.co.uk/filters.html

>> >

>> >The charts are very interesting, showing how the UV filter is a radically

>> >different animal from the Skylight. The UV behaves in a similar fashion

>to

>> >the Yellow, Orange, and Red filters, in that it passes everything, with a

>> >'flat' transmission curve, above a certain wavelength, and then cuts off

>> >quite sharply below it - it is just that for the UV filter it starts to

>> >attenuate when we are nearly out of the range of visible light and its

>75%

>> >point is already into the UV, whereas coloured filters for B&W are of

>course

>> >cutting off visible light as well.

>> >

>> >The Skylight is entirely different, behaving much more like a light

>> >balancing filter - which in effect it is. Its transmission line wavers

>> >somewhat, having a gentle dip in mid green, and then it too attenuates

>UV -

>> >but not as strongly as the straight UV filter does. This last point

>might

>> >be salutary for anyone going to the mountains who assumed that the

>> >'stronger' Skylight filter would be better than the UV filter for

>> >controlling excess UV, an assumption I might have made.

>> >

>> >A filter described by Pentax as "Cloudy" is basically their 81A (bit like

>a

>> >Nikon A2) so this too is a light balancing type filter, with a much

>gentler

>> >roll-off than the UV. This filter attenuates UV more than either of the

>> >other two (though it lets through a little of the very short wave that

>the

>> >UV attenuates completely) so would be a far better choice than the

>Skylight

>> >for the mountains, or the beach.

>> >

>> >And my point is?

>> >

>> >Well, apart from all this being interesting in itself; I can agree that a

>UV

>> >might well make no really visible difference with B&W film versus no

>filter:

>> >any situation where there is a lot of UV around, most of it will be

>> >scattered anyway, the B&W won't show a colour cast, and so the only

>effect

>> >will be a slight softening, if there is any visible effect. It might

>even

>> >be beneficial in some circumstances as it will reduce shadow density.

>The

>> >UV probably still would help with distance shots where there is a lot of

>> >scattered UV in the air causing 'haze' - but then a yellow or stronger

>> >filter will do the same job only 'more so'. The Y, O and R filters for

>B&W

>> >all have sharp cut-offs that mean that as well as the visible light they

>are

>> >attenuating, they are also taking out all the UV that a UV filter would

>> >remove, so a Yellow filter for B&W will usually make more sense as a

>'basic'

>> >filter than a UV does.

>> >

>> >But I doubt that it will be true a UV makes no difference with colour

>film,

>> >where UV light will tend to give excess blueness, as well as to reduce

>> >contrast overall, and add 'haze' to shots with a lot of atmosphere

>between

>> >lens and subject _if_ there is a lot of UV about to start with - at the

>> >beach or in the mountains, or in a dry desert. (Of course, the beach and

>> >the desert are places where you might use a UV for 'protection' anyway.)

>> >Uncoated flash tubes - some older studio flash heads, for example - also

>> >often give out quite a lot of UV, and the normal advice is to filter for

>it.

>> >

>> >It is true that all glass absorbs some UV, but I don't think normal

>optical

>> >glass has anything like this degree or steepness of attenuation: I'm

>> >recalling that one can still get sunburn through a window, and also that

>> >sunglasses don't block UV unless they are specially formulated to do so.

>> >All glass absorbs some, so a multi-element zoom may well show less effect

>> >from UV than a 'minimalist design' standard lens, but _so long as there

>is

>> >UV in the scene to begin with_ I would expect some effect from the

>filter.

>> >

>> >David - any comments? I know you've done some testing, but how much UV

>was

>> >actually present in the light you used for the tests? I'm hypothesising

>> >based on the transmission charts, so would be interested in anyone's

>> >comments.

>> > Peter

>>

>> Whew!

>> But, the problem is: it is very easy to theorize,

>> given a bunch of data - but the "bottom line" is:

>> "What is the visible effect in a photograph taken

>> under normal conditions?" Set up a camera and lens

>> (preferably one of, say, 5 or more elements), and

>> shoot a scene at normal altitude (say, roughly

>> 1000'), in normal weather (say, "cloudy-bright",

>> with some blue sky showing), with a good range

>> of average subjects (trees, grass, a building, a

>> nearby person, etc.) with a standard panchromatic

>> B&W film with standard processing, with in turn

>> no filter, a UV filter, a skylight filter, then a

>> light yellow, medium yellow, dark yellow, orange,

>> red, light green, dark green, and a blue filter,

>> carefully applying the appropriate filter factor

>> to the original exposure (instead of using the

>> color-inaccurate camera TTL meter). Include a

>> grey card for reference. Make sure that the

>> lighting does not change appreciably during the

>> shooting, and that the angles and subject

>> positions do not change (this takes a bit of

>> pre-planning and fast work...;-). Process the

>> film and make a contact print, being sure that

>> the printing illumination and sheet development

>> are even. This, I think, will honestly represent

>> the results for 99% of shooting, and I think you

>> may find the following: no discernable important

>> image differences for the no-filter, UV, skylight,

>> light-yellow, medium-yellow, light-green, and

>> blue filters (the last three may show VERY slight

>> differences, if you look VERY hard - but is

>> this worth using them for...?;-) The dark yellow

>> will show a slight darkening of the blue areas

>> in the sky; the orange will show some more, and

>> the red will show more yet - but not a lot, unless

>> the blue is quite pure (plus some slight darkening

>> of the brightest greens). The dark green will show

>> VERY slight lightening of the brightest greens,

>> but the effect will be very moderate. If there is

>> a "distant" part in the subject choice, you will

>> see no difference in the level of obscuring haze

>> with any of the filters, compared with no filter.

>> Sorry....! ;-)

>> Even "sharp-cut" filters pass some of their

>> opposite colors, and rarely in nature are colors

>> very pure, so the effects of filtration on tonal

>> relationships is generally subtle, with the orange

>> and red filters (particularly with a clear blue

>> sky) showing the most effect - but on a grey day,

>> even these strong filters will show little effect.

>> And, lenses do not pass enough UV to matter very

>> much, unless the lighting conditions are unusual.

>> I find instruction books and filter ad sheets

>> purporting to show the wonderful effects of the

>> various filters on images rather entertaining...;-)

>> David Ruether

On Thu, 30 Jan 2003 03:10:39 GMT, "McLeod" <wmcleoa910@rogers.com> wrote:

>Slight differences? This is one of the very first assignments our students

>do when learning about b&w film, processing, printing and the wavelengths of

>visible light. In fact, there have been generations of photographers who

>have photographed the fire hydrant against the grass outside the front door.

>The differences are quite dramatic. If I can find some examples tomorrow I

>will post them.

This was my point: for most average subjects, under

most conditions, the differences with most filters

will be minor; with high-saturation colors (mainly

the sky in nature, though flowers, hydrants, etc.

are also notable) the differences *are* noticeable,

but why would you want to modify the tonality of

a hydrant, car, flower, etc. (with the exception of

the sky...)? Otherwise, you are just doing meaningless

exercises, like using inappropriate color-correction

filters with slide film...;-) Sure, I can shoot a color

chart with B&W film using various filters and "prove"

their effects - but in MOST "real-world" shooting, it

is useful to know that the effects of most filters are

too subtle to worry about (or spend the money on, or

lose the effective sensitivity for, etc.). This is a

more useful lesson for students than finding the

few exceptions, I think...;-)