use of a densitometer

Discussion in 'B&W: Film, Paper, Chemistry' started by ader, Jun 4, 2003.

  1. ader

    ader Member

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    Hi,

    I have worked with two different photographers recently and found varied views on the densitometer. The first said to test his film and camera he uses a subject with a five stop difference plus a piece of photo paper with 1/2 stop increments going up from total black to total white and gauges his EI and develpment from there. The other photographer does all that plus uses a densitometer to see if he is getting correct denity on his negs. both the results look the same too me and the first photographer has no use for densitometer. i know they measure density on the neg but couldn't a person already tell that with the above tests anyway. so I' m wondering what is the practical value of a densitometer to the pro photographer.

    ta Ader
     
  2. Donald Miller

    Donald Miller Member

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    You are correct that many photographers do not use a densitometer in establishing the EI of the film that they are using or the development time of the film. In fact many do achieve remarkable results.

    To answer your question regarding the practical purpose of a densitometer. The densitometer will more accurately determine the actual EI of the film and the contrast range of the negative.

    I have done it both ways. With TriX I established through the use of a densitometer the actual EI of the film was 160 rather then 320 as advertised. With Bergger BPF I arbitrarily established 64 rather then the 200 as advertised. I exposed two identical scenes with both TriX and Begger. I placed an important low value at a Zone II luminance. When the film was developed the TriX is properly placed. The Bergger Zone II value is too high and shows more detail then desired. So I will either need to arbitrarily set a higher EI for Bergger or actually do the testing with a densitometer.

    I hope that this answers your question. Good luck.
     
  3. Jim Chinn

    Jim Chinn Member

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    In some ways it is simply a matter of how one approaches the craft. The densitometer is a great tool for someone who is very analytical and likes a certain amount of precision and consistency. It allows you to compare batches of film, match negs to paper and very usefull in determining what exposure is best for certan films that wil be printed via alternative processes.

    However, what makes makes an ideal density range for me may be different for others. I have gotten used to the practice of photographing certain "test" scenes, developing test shots at various times to produce the "right " neg and then printing for evaluation. This can be a long process with a new film, light meter, or recently purchased used lens etc, but I am a visual learner and have to see results as a picture and not a graph.
     
  4. Tom Duffy

    Tom Duffy Member

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    My understanding is that a densitometer can be used to establish your effective film EI and effects of on highlights of various development times. Taking it to the next level, as Phil Davis does in "Beyond the Zone System", you can tie your film/ developer combination to the appropriate photographic paper.

    Much the same results can be arrived at experientially For example, if I find I want more shadow detail in contrasty situations I lower my EI. I normally rate Tri-x at 160. I also cheat a bit when I develop sheet film...I take two exposures of each subject and develop one sheet for 6min and the second for 8min-then print the one I like the best.
    I have no doubt that taking a systematic approach to testing would provide a firmer basis for your work, for the evaluation of new materials, etc., but I also believe it's unnessary.

    I believe its much more important to pick a paper that works well with your film and developer combination. This can certainly be done with a densitometer, but it can also be done visually.
     
  5. DKT

    DKT Member

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    Probably most pros would be using densitometers to read control strips for tracking the process control of whatever they're running--E6, b&w, C41, RA4 etc. I use one where I work to measure E6 control strips and occasionally do Kodak b&w control strips as well. You'd use these in setting up a deeptank line or a processor more or less--for the b&w, you measure the "contrast index" which is calculated off a couple of densities on the control strip and corresponds to how well a given time will produce a neg that prints on grade 2 paper. Once you establish a standard dev time for a given CI, you can then figure out higher or lower CIs and additional dev. times. In the end, if your process remains consistent, you have a pretty good idea of what times, i.e. batch times, to set up processing runs if you have to run alot of different types of film....you also use the control strips to monitor your process & track replenishment, fixer activity etc. For b&w you can pretty much do this without a densitometer--it's pretty easy to figure out film speed by doing ringaround tests with gray cards, but for any color work you would definitely need one at a certain point. In E6, the strips are used to set up the first dev. time, which sets film speed. You also use them to monitor other steps that ulitmately effect color balance etc. FWIW, the densities you read are plotted on a graph--chart--against "aims". You have a certain amount of tolerance to work within on the upper & lower sides of the aim. For b&w the aims are set, but for color they vary by the emulsion batches of the control strips. The aim for this is reached by initially reading the "reference strip" which comes with each box of control strips. The point in the end, is to aim for a standardized process, and you really need a densitometer for this sort of work, although what you're doing is reading control strips really, checking them against the manufacturer's standards.

    KT
     
  6. Jorge

    Jorge Inactive

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    I could not disagree with Tom more! I find a densitometer invaluable, specially if you are just beguining. Testes for correct film speed, testeting for correct developing can tell you if you are doing things right or not. In other words finding mistakes is a lot easier than if you say, well let me half the EI, or let me double it and lets see what happens if I do an 8 min developing.

    All this is fine if you are an experienced photgrapher and have some ideas based on that exprerience, but if you have no experience this type of working method will lead to frustration and many, many wasted sheet os film.

    Of course also depends on what you do, I print in pt and could not live without one, t saves me a lot of money, but if you are a commercial photographer, doing work with digital backs, you definitly do not need one.....
     
  7. RAP

    RAP Member

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    From the comments here, it seems most rate their TRI-X about the same. I know Barnbaum also rates his at 160. In AA's book, The Negative, he also rates TRI-X at 160, FP4 at 64. I think Sexton rates T-MAX 100 at 50 to 64. Me, TRI-X is rated at 200, FP4 at 75, Pan F+ at 25, T-MAX 100 at 50.

    It would seem that most rate their B&W films one stop slower then what the manufacturer recommends.

    The variable for film speed is the exposure meter. I think the most popular is the Pentax Spot. Mine, a Soligor. With so many using almost the same equipment, it seems fitting most would have similiar ratings.

    Film manufacturing is pretty consistent so just how much difference can there be, 1/2 stop at the most?

    I do not own a densitometer, though sometimes I wish I did, and I may buy a cheap one in the future if I find a good deal. But great imagery does not start in the darkroom. Too much testing and experimenting can drive you nuts.

    BTW, ordered more old emulsion TRI-X 4x5 on Tuesday from Calumet. They said they had about 100 boxes left.
     
  8. avandesande

    avandesande Member

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    Isn't it really possible to do all the things a densitometer will do with a scanner and step wedges?
     
  9. Loose Gravel

    Loose Gravel Member

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    I should think so, but I have a densitometer and no scanner.
     
  10. ader

    ader Member

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    Ta for your answers,

    is there a website that has info about how to interpret densitometer readings ???it appears that if is handy to determine a better EI than it can only be helpful in the long run !!!

    ta ader
     
  11. lee

    lee Member

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    If you are looking for the ei only then a series of exposures that range from 3 stops under the meter reading to 6 stops under the meter reading in half stops should be adequate. Leave one or two frames (with roll film and 35 mm) blank. If you are testing sheet film, toss in an unexposed sheet. Process as normal. Now after the film is dry, use the densitometer to determine film base + fog by measuring the clear frames or clear sheets. Write that number down. Now measure each frame and find the frame that will be the nearest the .10 density. This number will be the ei of that film. Don't forget to subtract the film base + fog and then find the .10 density. keep good notes so you will know what frame is what.

    To find the development time, we are interested in the frame about 3 stops over the meter reading. Run the test and start 2 stops over to say, 4 and one half over. Process the film at the manufactures published time. Using the densitometer, find the density that is closest to 1.20 for condeser enlargers and 1.30 for diffusion enlargers. If you are way under processed or way over processed, then another test is needed. Way over is generally the problem. Start to process the film and reduce the process time by about 20%. Read the film and adjust as necessary. Pretty simple if time consuming.

    lee\c
     
  12. mvjim

    mvjim Member

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    A quick suggestion to RAP's reply - It should be noted that the photographers he mentions (Barnbaum, Sexton, Adams) all shot or shoot large format. If ytou are shooting smaller format you might find that these ratings are not in line with what you desire. Its always best to take the film for a "test drive" meaning - shot, develop and print on the grade you like and at the size you wish to print. If it is not correct, then make your adjustments accordingly.
     
  13. Donald Miller

    Donald Miller Member

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    As a reply to mvjim.

    I agree that sheet film and roll film considerations are not the same.

    Typically the published desired densities for sheet film reflect the desired grade two paper grade.

    Roll film will benefit from a development that will allow printing on a grade three paper. The reason that I say this is that roll film will benefit from lower development times that will reduce the formation of visible grain.

    This will still allow the availability of grades four and possibly five (depending on the paper chosen) for expansion of contrast. It will allow grades two and one in the event that contraction of contrast is desired.

    I don't think that if all things are equal (the same film emulsion and accuracy of lens shutter speeds) that roll film will benefit from a different EI then that determined for sheet film. The film emulsion is governed by laws of sensitometry and thus it requires a given quantity of light to expose a given film emulsion. The emulsion characteristics give no weight to differing film formats.