Brian Pritchard

Base fog density is the densitometer reading for unexposed film after processing. In the case of colour film it would be Red, Green and Blue densities and for Black and White film a visual density. The fog level will increase as film gets older and also it will increase with push processing. The higher the base fog level the lower the maximum black you would get in a print. Labs will often test samples of old batches of film stock by processing a piece of unexposed film and reading the base fog density. If it has been badly stored or very old then the fog level will be high and the film should not be used. Brian

MGM had a Black and White Laboratory at Borehamwood Studios. It closed. I think. in the late 1960's or early 1970's. Metrocolor was the new name for Kay labs when they were bought out by MGM. They were eventually taken over by Technicolor and closed down in the late 90's. I have a sensitometric pad in my collection of useless rubbish that cams from MGM Labs. Brian

Also Technicolor are moving from West Drayton to Pinewood in the next few months. Brian

As I understand John, Ascent Media, owners of Todd-AO and Soho Images, have already moved the processing equipment to Soho and the staff at both labs are under notice of redundancy. Todd will close in the next month. Karl, you are welcome to publish the details, glad to help. Brian

I maintain a list of motion picture labs in the UK both past and present (a lot more past than present!) on my website at http://www.brianpritchard.com/British%20Labs.htm. There are 12 labs operating in the UK today although that will drop to 11 in the next few weeks when Todd-AO close. The list does include the National Archive Laboratory which is not actually a commercial lab but I try to include every lab that has ever existed in the UK. I am always pleased to hear of any errors or omissions. Brian

The latitude of a film depends on the length of the straight line portion of the characteristic curve, the contrast of the film and the brightness ratio of your subject. Kodak Plus-X negative and Kodak Double-X negative have very similar characteristic curves as far as length is concerned. They will accommodate an exposure range of roughly 1 to 100. If the brightness range of your subject is 100 to 1 then there will only be one correct exposure and no latitude; if the brightness range is 1 to 10 then you will have a wide latitude of exposure. Changing the development time will change the contrast of the film and will change the latitude. As the contrast goes up the latitude goes down. Black and white reversal films are processed to give a projection contrast result and are therefore much higher contrast than a negative film and will have less exposure latitude. Brian

Intermediate Stocks are designed for use in film recorders and film printers so they are all tungsten balanced. 5242 has a contrast of 1.0, normal camera stocks have a contrast of around 0.6. I estimate that 5242 has an ISO rating of around 1. There is an additional problem in that this stock is designed to print from masked stocks, either colour negative or an interpos, so you would need to use a Wratten 85 to correct for that and another 85 to convert the light source from daylight to tungsten, this would drop your ISO rating even further. Internegative stock would only need a single 85, it's speed is around the same but it's contrast is around 0.6. Brian

The Kodak Booklet om B/W Processing states ' Reversal films lose 2/3 stop when processed as negative.' It recommends overexposing by 1 stop but says you can use the latitude of the film and overexpose by 2 stops but you might have to adjust the processing. Hope this helps Brian

Both Kodak and Fuji put manufacturing date codes on their film stocks, however it is a latent image so you have to process the film to see the codes. You should remember that how the film has been stored is almost more important than the manufacturing date. You should do a clip test to check the stock before use, you would also be able to see the date code then. A stock that has been correctly stored for 3 years could be in better condition than film 1 year old that has been badly stored, so you should always test stock if there are any doubts about its history. Brian

One of the best articles on B/W Reversal Processing is: 'Processing Methods for Use With Two New Black-and-White Reversal Films' by C E Ives, J W Zuidema, N A Exeley and CC Wilt of Eastman Kodak. This was published in Jan 1957 in the Journal of the SMPTE Volume 66 Number 1. It gives lots of advice and processing times and formulae. It also covers processing in a hand tank. I have a copy of this which I will scan and put on a file sharing website. If anyone wants to download it just drop me an email to mail@brianpritchard.com. Please put 'BW Reversal' as the subject so I can spot it amongst the vast quantity of spam I receive. Brian

Actually it is the other way round; reversal stocks have thicker emulsions. Most B/W films can be processed as negative or reversal. One of the exceptions is reversal film that has a silver anti-halation undercoat you cannot process these films to negative as they require the bleach to remove the undercoat. You should be able to get a good result from 7222 as reversal but it is important to get all the processing steps correct and particularly the re-exposure correct. Too little exposure will give very poor results and actually it is also possible to give too much re-exposure and the film will start to solarise. I should think in my time in labs I have processed most B/W films as reversal including positive stock, used for titles as it is better to shoot white letters on a black background and reversal process as it keeps flare to a minimum. Brian

John You could try 2238 Pan Separation Film and process to a gamma of 1.0, or a bit less if you are using an Oxberry, for the dupe pos and dupe neg. 1.0 x 1.0 gives an overall gamma of 1.0 which is what you require. I have used this method and the result is quite usable. Brian

It is usually A wind or Double perf. Most contact printing machines take A wind or double perf film stock. If you need B wind you just have to rewind it, although the edge numbers will be backwards. Brian

The various film exposure ratings were introduced as follows: H & D 1890 Scheiner 1894 Weston 1931 DIN 1934 1957 changed to match BS/ASA BS/ASA 1947 H & D (Hurter and Driffield) were the people to invent the characteristic curve in 1889 and also invented their exposure rating system, firstly for plates. The difficulty with the different systems is that they are not directly comparable as they all used different formulae for calculating the speed also they use different systems for the progression of speed. H & D gives a speed of 250 for a film and a film 10 times faster will have a speed of 2500. With DIN and Scheiner the progression is logarithmic. 300 H & D is roughly equivalent to 18 Scheiner, 8 DIN and 5 ASA. 2000 H & D is equivalent to 30 Scheiner, 20 DIN and 80 ASA. In the 1940?s HP3 had a speed of 5000 H & D, 32 Scheiner, roughly 200 ASA. Brian

I have been searching to try to find in the literature somewhere a film speed being quoted. I have searched through SMPTE Journals back to the 30's without much luck. The only useful fact I can find is in 'The Condensed Course in Motion Picture Photography' edited by Carl Louis Gregory from 1920. In this book he says that the normal exposure for Eastman B/W negative in sunlight was f4.5 at 1/50th sec. I calculate that this equates to an ASA speed of 3. I believe, and I have to admit I am not a cameraman just a humble film lab technician, that the exposure at 1/50th sec for a 25 ASA film would be f11. So the estimate of 2 - 3 ASA was very accurate. Brian

Yes, it was made in Harrow, certainly in my time at Kodak. Brian

Apologies for the long delay, I have located data sheets for Eastman Color Negative 5254 and Eastman Color Negative II 5247. I also came across the datasheet for Eastman Color Negative 5248 introduced 1952 replaced by 5250 in 1959. I will scan these to a PDF file. If anyone wants the file emailed, please email me at mail@brianpritchard.com with the subject 'Datasheets' so it does not get lost in the spam filter. Brian

A lab will always join up camera rolls into large rolls fro printing. It does depend on individual labs on what size rolls of stock they use. It would usually be 2000ft rolls. It takes about 30ft of leader to print a roll which you have to pay for, so joining them up saves stock and lace up time for the lab. The same applies to telecine where you will have to pay for the lace up time. In the past labs would employ people to remove NG takes and join up the good takes before printing, again to say costs. It is a long time since I heard of that happening. Brian

Cal , The other thing to bear in mind is at that time there were a number of print stocks available. Although the camera stock might have been Kodak, the print stock could have been Fuji, 3M, Orwo, Technicolor or Gevaert. This of course will have a bearing on the final result on the screen. Similarly they might have shot on Fuji and printed onto Gevaert and so on. And also the duplicating route can come into it, whether an interpos/ dupe neg was made or a CRI or Technicolor Matrices. It gives an awful lot of combinations. I will try to go through my datasheets this weekend. Brian

i have a fairly large collection of data sheets of film stocks from this time, I will have a look and see which ones I have. Brian

The various edge printing should appear as black on the clear negative background. There should be the stock manufacturer's name, footage numbers, date code and various barcodes and stock emulsion numbers. There is always the possibility that the edge printing was left off a roll but if you have several rolls that is unlikely. Tne other possibility is that the tests were not developed for long enough to bring up the edge printing. There are lots of samples of edge printing on my website www.brianpritchard.com if you want to see what they should look like. I am assuming that your clip tests were at least a foot long and were not fogged; the edges have to be clear to see the printing. Brian

Fuji identify the date by putting a two figure year code and a two letter quarter code. JM- Jan-Mar; AJ April-June; JS July-Sep; OD Oct-Dec. You can see a sample on my website at http://www.brianpritchard.com/Date%20Codes.htm Film manufactured this month would have 08 - JM Brian

I do not know of any way you can tint the film base. Tinting always applies to tinting or dyeing the emulsion. The stock manufacturers added the colour during the manufacture of the film base. Incidently dyes were also used for hand colouring and stencil colouring of the emulsion. Some really beautiful results were obtained where they used 4 or more dyes on each frame. Brian

Actually when tinting first started it was carried out using dyes to dye the emulsion. It wasn't until later that the various stock manufacturers introduced B/W Pos films with colour bases. There are labs, such as Prestech in London, that can still carry out tinting (and toning for that matter). Some of the dyes used in tinting have safety implications. If you just want to experiment you can use food dyes which hopefully don't have Health and Safety problems. They will not be as stable as using the correct dyes but it is fun to try. There is no problem in tinting acetate or polyester films. And thanks Henry for your kind remark about my website. The Eastman Kodak publication 'Tinting and Toning Eastman Positive Films' published in 1922 is available to read on my website at http://www.brianpritchard.com/tinting_and_..._eastman_po.htm Brian

There is not a lot of information in the literature about developer dilution. The development rate compared to the dilution does vary according to the developer composition. Metol/Hydroquinone developers do not have a linear response; you require proportionally more time as you dilute. The other thing is that as the developer concentration is reduced the maximum contrast obtainable is reduced even with increased time. You do tend to get finer grain and increased edge effects from a dilute developer. In the stills world some developers are used very dilute in order to get the highest definition from edge effects.. You are suggesting a dilution of around 12.5%. My guess would be that you should increase the time by about 15%. I would do the same for the clearing bath, bleach and fix. These baths are not terribly critical as long as you give sufficient time so perhaps 20% would be safe. As always you should do a test to be sure but, of course, that is not always possible. If you are not worried about a bit of extra contrast you could increase the development a little more, remembering that if the first development produces a heavy image your final image will be thinner. You didn't say but I have assumed that you are B/W reversal processing. Brian