Brian Pritchard

Thanks for the correction, Brian. That's a very useful site, well worth bookmarking.

 

 

 

-- J.S.

You will find all the information you want to know about film sharpness in the book 'Fundamentals of Photographic Theory' by T H James and George Higgins of the Eastman Kodak Company. Chapter 13 covers 'Structure of the Developed Image', page 280 onward has a section on Turbidity and Sharpness. Basically sharpness is defined as the density gradient across an exposed knife edge. In theory the image should go from black to white, how quickly the change takes place defines sharpness. It is measured by using a micro densitometer across the image.

Brian

The way they determine sharpness is by shooting a test pattern and measuring density on the film to create a graph of the Modulation Transfer Function, or MTF.

 

The test pattern consists of alternating black and white lines, ranging from wide to narrow. On the wide end, you see clear black and white lines, 100% modulation transfer. On the narrow end, the lines disappear into gray, 0% modulation transfer. I don't know off hand exactly how they turn the in-between density readings into percentages, but they come up with a graph that starts out horizontal at 100%, then curves downward until it hits 0. The narrower the lines where the curve heads south, the sharper the film.

 

A similar thing is done in video, where for lengthy historical reasons, the pattern of fat to skinny lines is called multiburst.

 

 

 

 

-- J.S.

The pattern is actually sinusoidal pattern of increasing frequency. Some films produce a result that has MTF of low frequencies that is greater than 100% this can be can be caused by developer edge effects.

You can find a full explanation here http://www.normankoren.com/Tutorials/MTF1A.html

MTF is also used to measure lenses and the results can be multiplied to give the combined result for lens and film and so on.

Brian

Dominic, I thought you had gone walk-about into the outback; I must admit I was beginning to feel overwhelmed. Of course I agree with what you say, a very clear and succinct reply. Perhaps I do know a little about push processing after all!

Brian

This is factually incorrect... Pushing can (not) bring out information where no information exists... it can not just 'make it up'.

 

This topic may be exhausted for you, however, the more you write the more there is to discuss ;)

The whole point I have been trying to make is that the information is there. The more you develop (with-in reason) the more the information you will pull out.

Brian

Besides the decrease in grain perception (esp. in S16), this is another good reason to rate stocks 2/3s slower... Most underexposures are between 2/3 and 1 stop under so, if you forget to compensate for an 85 for example, you are still in 'normal' range.

 

I have to agree with Mr. Pritchard and anyone who has ever pushed has heard the lab express to them that they will not yield a full 1 stop on a 1 stop push. I also think there is a bit of semantics going on in that pushing does not increase speed (on the low end) because as David M. stated.. it occurs after the fact and we can not bring to life something that is not there in the first place. At the same time, pushing can bring to life things that are under between the mid and lows.

 

On the Fotokem Test I saw no increase in Contrast or Grain in a 1 stop push (which is really 2/3s) in either 35mm or S16mm.

I think we have nearly exhausted this subject.

However I do not accept that because you have already exposed the film push processing will not yield an increase in speed. As the Kodak website explains if you push by 1 stop you get an actual increase in speed of 1/3 stop. The film records all the information that is available. Some grains will not receive sufficient exposure to be able to be developed at a particular film speed, if you then push process these grains will be developed and you will gain information.

Film does not just stop recording at a particular light level, it is a case of whether the grain has received sufficient exposure so it can be developed. Extra development will develop grains that would not be developed with less development.

What we are talking about is the difference between push processing and intensifying. If you intensify a B/W negative that has already been processed you cannot bring up any more information, you just make the negative heavier. If you give a B/W negative extra development you will bring up extra information. This is why manufacturers give different exposure ratings for different developers for B/W still stocks. Colour negative is no different. Working on a processed colour negative digitally is the equivalent of intensifying it and cannot produce additional information that is not already there. Push processing can.

Brian

So even if there is a slight speed increase, which I am willing to concede, you don't get an extra stop's speed with a one stop push, even if you start out at an EI of 250 with a 500T stock.

Karl, if you read my posts carefully you will see that I did not state that when you push 1 stop you get 1 stop increase in speed.

If you want to see what Kodak have to say about push processing then this is the link.

http://motion.kodak.com/US/en/motion/Suppo...mation/push.htm

This is what they say about speed increase:

Speed:

ER speed increases with Push processing may be significantly less than needed to offset speed loss from under exposure. With the given conditions above, Push 1 processing produces ER speed increases of less than a 1/3 of a stop and Push 2 produces ER speed increases of around 1/2 of a stop. Push 2 taken in combination with two stops of under exposure represents a stop and a half loss in real speed. The end result is smoky shadows in prints.

Brian

I also meant to say you only have to compare a Kodak control strip normally processed with one that has been push processed to see that extra steps are revealed indicating that there has been an increase in speed.

Brian

Brian, I don't understand how you can believe that forced processing will increase the sensitivity rather than just increase the density of the negative. The sensitivity of the stock is based on the size of the grains and their efficiency in capturing light. Forced processing comes after exposure so it can't go back in time and make those grains better at capturing photons. It can only take what was captured and increase the percentage of silver halide grains that get converted to silver. That's not an increase in sensitivity but it does compensate for underexposure by taking what did get captured and increasing its density back to normal levels. So it can allow one to rate a stock faster but it is not a true increase in the sensitivity of the stock.

Push processing does give a real increase in speed. The information is captured by the emulsion, the amount of information that appears on the film will depend on the amount of development. If you under-develop (pull process) you will lose some of the recorded information and likewise push processing will bring up information that you would not get if you didn't push. It is not a question of making grains better at capturing photons they have already been captured and require the extra development for them to be revealed.

Brian

It's amazing how many people on here (not calling you out Dave M., but you Brian) don't understand pushing.

Wow, I have worked For Kodak Research, been Technical Director of three labs including one of the biggest in London, I have been in the industry for 49 years and I still don't understand pushing. Time I gave up.

Brian

Pushing can't add information that wasn't originally captured, it just increases density on the negative to what did get captured, while increasing contrast, the base fog level, grain, and to some degree, there is a bit of a color shift to the blacks.

This is just not true. it would only be true if you did not get an actual increase in speed with push processing. I measure sensitometric strips on a regular basis and you can see the speed increase when you push process.

If you push process a 50 ASA film 1 stop, then it is, as far as exposure concerned, equivalent to using a 100 ASA film, so you will have more information than if you used the film at 50 ASA. If the push processing is giving an actual increase in speed then you will have more information than if you did not push. If you under-expose by one stop then iDI cannot bring up information that is not there.

Push processing will increase contrast, base fog level and grain but if you desperately need detail in the shadows you need to push process if the film is under exposed.

Brian

Shadow detail can't be gotten back from a push, though, just highlight and contrast can be pulled up.

Not correct I am afraid, the whole point of pushing is to increase the shadow detail. In fact it is possible to lose detail in the highlights if you push process but normally if you are pushing an under-exposed scene the highlights will just increase in density.

Brian

I believe that it is worth pushing up to 1 stop. You do get an actual increase in speed (probably not a complete stop). If you process normally so that the film is effectively underexposed no amount of DI work will retrieve information that is not there in the film. You will be able to increase the contrast and density with DI but that bit of extra processing might just retrieve some vital information in the shadows. The extra processing will increase the contrast and the grain but that might be acceptable for the extra information you obtain.

Brian

Three 1.33 4-perf 35mm images gets you 3.99 : 1.

 

The Cinerama format used three 6-perf 35mm frames about 0.88 : 1 each for 2.66 : 1 total.

Actually if you want to be pedantic the SMPE 1922 Standards give the projection aperture as 0.748" by 1.109" which gives an aspect ration of 1.333333 reoccurring - 1.333333 x 3 = 3.999999 which as far as I am concerned is 4.0 to 1.

Some other facts that come from these standards are that the camera cranking speed was set at 60 ft per minute and the projection speed at 80 ft per minute. It also states that any new formats should retain the 4:3 aspect ratio - nobody listened to that!

The 1922 standard was the point where the primary measurement for '35mm' film was changed from 1 3/8 inches (34.95mm) to 35mm.

If you are interested in these standards you will find them at http://www.brianpritchard.com/SMPE_Standards.htm

Brian

Keeping with the discussion of aspect ratios, I recently came across a discussion of Abel Grance's film Napoleon. Apparently, Grance intended Napoleon to be projected using "Polyvision", an extreme wide-screen format with an aspect ration of, (get ready!)...4.00:1. It is supposed to be three 35mm projectors projecting the film on to a screen, but that sounds oddly familiar to Cinerama which has an aspect ration no where near 4.00:1. Does any one have any insight on this beast of a format?

The final reel of 'Napoleon' is designed to be shown as a triptych using three projectors so you get 3 x 1.33 (the silent format) giving 4.00:1. The remaining reels are normal silent aperture. It has been shown in London at the BFI using three projectors and elsewhere I believe.

Many archives still show silent films using the 1.33; 1 aspect ratio.

Brian

I'd expect the big difference to be between workprints and answer prints direct from the original negative on one hand, and check prints and release prints that are IP/IN generations away.

 

I looked around on the internet for info on the classic Bell & Howell model C and J printers, and came up empty. So, I have a request for the actual lab guys who have access to this kind of equipment (Dominic, Robert, Karl, anybody else?): Could you please shoot some digital stills of your printers and give us a little show and tell on how they work? It's a part of the process that a lot of us know nothing about. Perhaps it could be saved here as a FAQ.

 

 

 

Thanks --

 

 

 

 

-- J.S.

You will find information on the B & H Model D and J on my website http://www.brianpritchard.com/Model_D_&_J_Printer.htm

There is also a picture of the Model C lamp house.

Brian

What would effect *perceived* sharpness is density and color correction. On workprints, they don't use the same finesse, or they let the "new guy" do the timing.

 

Some labs may (just a guess on my part) run workprints through chemistry at the end of the day that isn't in control, but none of this should effect focus, perceived or not. I suppose if a shot is way under-timed, so that the print isn't dense enough, it may appear to be out-of-focus when the negative is not, but this would be due to halation, not the actual softness on the negative.

I don't know of any lab that would turn out poor quality work prints or 'let the new guy' grade them. Again I don't know of any professional labs that 'run work prints through chemistry at the end of the day that isn't in control'. Labs keep their processes in control all the time. When film was the only way to work labs made their work prints overnight so that the production company, cameraman etc could look at them first thing next morning, check them so that the set could be struck if everything was OK..

I worked at Humphires Film Labs when they were processing for Stanley Kubrik, he examined every frame of a work print and expected the Technical Director to come in in the middle of the night if there was a spot on the print.

If you produced low quality work prints you would soon lose the rushes processing and ultimately the bulk release.

Brian

Just look at the splice in the picture that is pretty standard some places cut off a length after the run because lame producers are so afraid of even one speck of dust which is not so much the lab's fault as it is the producers.

 

-Rob-

Whilst I would agree that a splice only takes up a couple of inches, every lab I have worked at in the UK always took 6 inches of film from the outside of the roll and taped it to the can so that if the processed roll had scratches it was possible to check for camera scratches by examining the section removed from the roll before processing. It also warned the processor if , for example, a roll of B/W negative had been sent in as Eastman Colour negative. You could tell from the colour of the base and emulsion.

Brian

I have extracted the following info for those who care - apologies to those who don't!

Type Sensitivity Photo Rec Speed Processing Base Backing ASA

2479 Extended Red Pan 500 Negative 4 mil Estar-AH Fast Drying (PX) 320 in D76

2490 Blue 64 Negative 4 mil Estar Dyed Gel

2492 Ortho 160 Negative 4 mil Estar Clear Gel

2494 Extended Blue 50 Negative 4 mil Estar-AH Fast Drying (PX)

2495 Ortho 320 Negative 4 mil Estar-AH Fast Drying (PX)

2496 Extended Red Pan 125 Negative 4 mil Eastar-AH Fast Drying(PX) 80 in D76

2497 Extended Blue 50 Negative 4 mil Estar Dyed Gel

2498 Panchromatic 320 Reversal 4 mil Estar-AH Fast Drying (PX) -

2 50 Negative 250 in D19

3493 Extended Blue 50 Negative 2.5mil Estar Clear

5498 Panchromatic 250 Negative 5.25 Mil Triacetate Static Resistant 250 in D19

250 Reversal

This information comes from datasheets dated 1980 and 1976.

Brian

Hello all,

I am wondering what purpose the RAR stocks were designed for? Are they infrared?

cheers,

richard

RAR stands for Rapid-access Recording. There were (are) a wide range of films for high speed photography, oscillograph recording etc.

The description of 2496 is: Kodak 2496 RAR film (estar-AH base) is a member of the Kodak family of RAR films designed especially for rapid-access recording and high temperature (up to 130 deg F) processing.

USES: Photorecording with artificial light (all sources) and daylight

Bubble chamber recording

Cloud-chamber recording

Modulated glow-tube (all types) recording

CRT photography (all phosphors)

2498 had the following uses:

Photorecording with artificial light (all sources) and daylight

High speed photography

CRT photography (all phosphors)

Spark chamber photography

I have datsheets for a number of other RAR films including some infra-red, if I remember correctly.

Brian

 

I have acquired three cans of Kodak Expression 500T 7284. It has apparently been kept in a fridge for the past few years. Attached is a photo of the label. Can anyone tell me how old this film is? Any ideas as to how this will look? thanks

7284 was introduced in 2001 so they could be up to 8 years old. The only people who can tell you the date from the emulsion numbers are Kodak and they don't usually release that information. If you have a couple of feet of one of the rolls processed it will give you a date code although it is not that relevant. What matters is whether the film has a high fog level and whether it has lost speed. You can check the speed with an exposure test and that or the short length processed to find the date will tell you about the fog level. If the film does have a high fog level then you will get a low dMax in your positive image - milky blacks.

Brian

Thank you.

 

I'm from the still photography world, getting in to cinematography and trying to find the similarities/differences of the more or less same products.

 

I've been using tri-x and plus-x in still. The ISO ratings are different in cine/still. I this because they are developed to a different gamma or are they just totally different films? Plus-x is ISO 80 on the negative cine film and 125 on the still.

 

BTW: Your website is very informative. Very cool.

 

Ulrik

I believe that the still and cine versions of Plus-x have a similar emulsion, however the cine version has addition layers such as a supercoat to reduce the possibility of emulsion scratches because the film is moving through the camera. The cine version is also perforated with BH .1866 neg perforations whilst the still version is KS .1870 pos perforations. I think the main difference between the speeds is that the still speed is calculated on the minimum exposure whilst the cine one has additional exposure to ensure that the shadows are not crushed and in addition the motion picture printing chain is nominally fixed as far as duplicating gammas are concerned. You don't have the option of using different grades of printing paper as you do with stills. Obviously if you get into the digital domain you have much more ways to manipulate your image.

Perhaps if anyone from Kodak is watching they can verify my thoughts or tell me I am

talking rubbish!

I use Plus-X Motion Picture negative for my stills, only because I can scrounge short ends. I expose it at 80 ASA and develop as for the stills film.

Thanks for the kind remark about my website.

Brian

Brian,

 

Sorry if this is slightly off topic, but is it possible to simulate the D96 process with a D76?

I read that they are essentially the same developers; D96 for transport/D76 for tank.

 

Is it then 6 min. at 20C in stock dilution?

 

I'm very interested, as I am trying to get an old film recorder calibrated. It's pretty far off in alignment and calibrations, so it would be great if I could get it within reasonable tolerance before sending test rolls off to the lab.

 

Thanks, Ulrik

The datasheet does not specify the dilution of D76, I would suggest it is not diluted but used as a stock solution.

These are the formulas for D76 and D96.

D76 D96

Water 750 mL 750 mL

Metol 2 gms 1.5 gms

Sodium Sulphite 100 gms 75 gms

Hydroquinone 5 gms 1.5 gms

Potassium Bromide 0.4 gms

Borax 2 gms 4.5 gms

Water to 1 litre

As you can see the formulations are similar; they have the same constituents but different quantities. As you mention D96 is for continuous processing machines with high levels of agitation and with continuous replenishment; D76 is for tank use and essentially is used as a one-shot developer, for this reason it has a higher level of preservative (Sodium Sulphite). The Borax is an accelerator and works in combination with the metol/hydroquione developing agents. Because of the higher agitation the D96 has less developing agents and more borax. The potassium bromide is a fog reducer and is only added when the bath is first made up, during use bromide comes out of the films so it is not necessary to add any during replenishment.

I am sure that you could substitute D76 for D96 but you would have to ensure that you had plenty of agitation and you would have to increase the developing time. As always a test would be wise.

Right that's it I am off to sit in a darkened room. Seasons Greetings

Brian

Also what is the difference between Latitude/Dynamic range? One I hear a stock has 7 stops latitude then I heard 16 stops dynamic range. So I am a little confused.

The dynamic range is the distance in stops from the toe of the curve to the shoulder. It is a measurement of the usable range of the curves. In the case of 7219 the range is 15 stops. That is the difference between your minimum exposure for shadows and maximum exposure for highlights.

Latitude is a measurement of how much you can overexpose from the minimum exposure that will record your shadows without crushing, to an exposure that will record your highlights without crushing. The latitude is entirely dependent on the brightness range of your scene and the dynamic range of the film. If you are shooting a gray card in a fog you will have a very low brightness range say 1 stop. In this case the latitude of the film would be 14 stops. If you are shooting a scene with a high brightness range, a polar bear in a coal cellar and the difference between the highlights and the shadows is 6 stops then the latitude of the film is only 9 stops.

Brian

Whoops - too much of a hurry. The time for 2496 is in D19 and for 2498 the temperature for D76 is 68 deg F (20C).

Brian

Hello Richardson

 

Sorry to take so lomg with the information - I had to dig the datasheets out from my loft.

 

2498 has a rating of 250 Daylight and 200 Tungsten When processed for 2 1/4 mins in D96 (Normal Motion Picture Developer) and 200 Daylight 160 Tungsten when processed as reversal.

 

2496 has a rating of 125 in tungsten developed for 1 minute at 95 deg F or 160 when reversal processed. You can also develop for 6 mins in D76 to give a gamma of 1.0.

 

I have copies of the datasheets which I can scan if anyone wants them.

Brian

Whoops - too much of a hurry. The time for 2496 is in D19 and for 2498 the temperature for D76 is 68 deg F (20C).

Brian