matt_t_butler

Thanks all for the clarifications, I wanted to know if the same FF exposures for contrast filters should apply to colour negative/slides - research for a project I'm currently exploring - some basic tests had me wondering if my exposures were wrong.

..... is it because panchromatic B&W film is sometimes more sensitive to the blue end of the visible light spectrum and the yellow, orange and red filters 'compensate' for this? I have used these type of filters with colour film and found the manufacturer's filter factors suggested are not always applicable.

My understanding of filter factors (which may be totally erroneous ....) is that they were originally designed primarily for B&W film. The popular landscape filters - yellow, orange and red block various amounts of blue light depending on the 'cut' of the filter. Given that the shadow areas in landscape photos are primarily illuminated by 'blue' light, is the filter factor compensation applied so a scene's shadow areas receive enough exposure and have some detail? Does this mean the similar colours in the scene (yellows, oranges and reds) are therefore a little overexposed by the compensation? I'm sure the answer would be found in a bunch of filter tests .....

..... a clever application!

...... B&W 5 x 7 contact printer? Is the ground glass similar to opal glass? Intriguing ....

Upon reflection (no pun intended) this could be from the top of a heavy duty rostrum 'down-shooter' camera set up used to photograph both flat art and 3D objects without the need to climb up and lean over the camera???

Does the device look like it accepts a 5 x 7 darkslide/film folder and is there a slot for an additional 5 x 7 filter in front of the film holder area?

Perhaps it is part of an opaque projector (epidiascope type device) for projecting 5 x 7 transparencies?

Back in the day Kodak suggested using two different filter sets - one for photography and the other for separation work. The camera filters were 'broadband' spectrum filters used in early 'one shot tricolor cameras' while the separation set were 'narrow cut' filters used to produce RGB copy B&W negs from Kodachrome and Ektachrome transparencies.

'In short, I'm pretty sure that with current technology any old reasonably dense RGB filters could be made to render acceptably faithful colour in the re-combined image.' Absolutely correct! Makes one appreciate the craftsmanship (craftspersonship?) applied to dye transfer and multi-colour print reproduction processes in the days before computers. As colour is fairly subjective and photograhic post-production applications are all encompassing, then modern RGB compositing is a matter of personal expression.

'Everything about the availability of RGB camera filters that you were afraid to ask ….. ' And yes - you can use some theatrical gels but they are generally not dyed to match the spectral response of their comparison lens filters and do not match the optical quality of glass. Great for experimentation - I once even used 'prime' Red, Blue and Green acrylic plastic (Plexiglass, Perspex) cut to 4" x 5.6" when I could not afford the glass filters. Gave an acceptable result.

If only, and duly noted ... probably should of said 'using this set on the camera for photography rather for copy/rostrum work'.

Everything about the availability of RGB camera filters that you were afraid to ask ….. Wratten (original Eastman Kodak) Tricolour photography suggested set for ‘one-shot tricolour cameras’ with B&W negatives #25 Red; #58 Green; #47 Blue - Early nomenclature ‘A’ (Red); ‘B2’ (Green); ‘C5’ (Blue) Tricolour set for direct separation (‘in camera’) B&W photography #25 Red; #61 Green; #47 Blue; Tricolour set for colour separation copy from colour transparencies #29 Red; #61 Green; #47B Blue These were the Kodak standards but photographers devised their own sets depending on film types and Daylight or Tungsten lighting set ups. Harris Shutter 1971 (Kodak AE-90) Mounted gelatin filters in a drop shutter #25 (Red); #61 (Green); #38A (Blue) Wratten 2 (contemporary Kodak) #25, #26, #29 Red; #58, #61, #99 Green; #47, #98 Blue #99 (#61+#16 Yellow/Orange); #98 (#47B+#2B Pale Yellow) Loading site please wait... Tiffen Glass filters #25, #29 Red; #58, #61 Green; #47, #47B Blue https://tiffen.com/film-enhancement/ Lee Filters for 100mm system Polyester Tricolour Red #25; Green #58; Blue #47B (0.1mm thickness) The tricolor polyester filters have been designed for tricolor photography and work well for that purpose. Dichroic filters (or any filters designed to go over lights) are not optically pure and would compromise sharpness when used over a camera lens. http://www.leefilters.com/index.php/camera-directory/camera-dir-list/category/tricolour Kenko The SP Color Set contains Red, Green, Blue filters for ‘factorization photography’ - similar to a set by Prisma released in the 1970s. SP Color Set- Kenko Global Site Cokin Cokin P Filter kit has a Red P003, Green P004 not suitable for tricolour work. (Needs clarification) https://cokinfilter.com/collections/black-white Formatt HiTech Various filters in #25 Red; #61 Green; #47 Blue Not listed on their website ? but available special order through B&H Photo NYC https://www.formatt-hitech.com/filters/ Formatt Hitech 67mm 47 Dark Blue Camera Filter HT67BW47 B&H Nikon R60 (Red #25); X1 (Green #11); B12 (Blue #80B) The X1 and B12 are unsuitable for true tricolour work B+W 090M is equivalent to #25 Red; 091M is a #29; 061 is #13 Green (No longer available?); 081 is a medium Blue (No longer available?) All are listed in their handbook but the 061 and the 081 are unsuitable for tricolour work https://www.schneideroptics.com/pdfs/filters/BWHandbook.pdf Moderator Note: Please see Post #37 by OP containing revised information.

For colour management when photographing objects we used to include a Colour Separation Guide at the side or bottom of frame - and crop it out later. Kodak make a large 13 inch one while Tiffen make a smaller 8 inch version. A cable release is also a good idea to minimize camera shake.

More Spiratone filter fun .... They also marketed a set of 3 'Vibracolor' filters: Aqua Blue ( Light Bluish/Cyan), Rose Red (a rebranded Wratten #32 Magenta) and Purple (a weird Birefringent Red+Blue). As well as their Contrast Blue which was a rebranded Wratten #47 Blue filter.

All about Wratten Tricolour Filters. Part 1 Background Wratten & Wainwright Ltd. was a small London photographic firm that claimed to be ‘the oldest established plate makers in the world, who specialise in materials for the Process Engraver and the Technical Photographer’ . Wratten ‘manufacture over 70 varieties of LIGHT FILTERS; the Wratten three-colour set is standard throughout the world’. (From a 1920s trade advertisement.) They produced experimental panchromatic plates which were a ‘considerable advance in photographic methods’. In 1906 C.E. Kenneth Mees joined the firm and ’made a series of light filters for use in the photography of coloured objects and to this day the ‘Wratten ‘ filters are standard in photographic work’. George Eastman offered Mees a job in 1912 ‘to organise and direct a research laboratory for the Eastman Kodak Company’. He agreed on the condition that Eastman buy Wratten & Wainwright Ltd. and the little business then relocated to the Harrow factory of Kodak Limited. Quotes from ‘Fifty Years of Photographic Research’, a talk given by C.E. Kenneth Mees at the Franklin Institute in Philadelphia on October 20th, 1954. (Dr. C.E. Mees was then Vice President in charge of research of The Eastman Kodak Company.) Applications In this 1916 list the filters are described with a letter which was the original nomenclature before the later adoption of numbers. A few have the application noted as a word. Very early filters listed are no longer produced.. For Tricolour work Standard Tricolour filters A(Red) #25, B(Green) #58, C(Blue) #49 Equal Exposure Tricolour Filters (for Cinematograph Work) E(Red) #23, B(Green) #58, C4(dark) #49B Tricolour filters for use with Artificial Light Stage Red #27A, B2(light) #57, Stage Blue #47A Standard Projection Filters (dark) F (…) #29, N(…) #61, Blue #46 {as per catalogue} Cinematograph Projection Filters (extra light) Projection Red #24, Projection Green #59, Projection Blue #47 ‘Wratten & Wainwright screen-plate analysis filters are: #29 or F for Red, #61 or N for Greenand #50 or L for Blue’ ( from a 1929 brochure.)

.... a little late but .... Originally the first standard Wratten tricolour photographic set of colour separation filters nomenclature was A, B2, C5. (#25, #58, #47) The letter code was changed to numbers around the 1940s (I think?) and the #25, #58, #47 became the standard for RGB separation photography - particularly when using 'one-shot' tricolour cameras. The other set was #29, #61, #47B - used to maker colour separations from Kodachrome and Ektachrome 5 X 7 transparencies back in the day. These are all still available as 3" x 3" Wratten gelatin filters from Kodak or reputable camera stores eg. B&H New York but are expensive - about US$75 each. Cheaper alternatives are available - for example, 85mm resin filters made by Format HiTech that fit the Cokin P system.