Enlarger exposure time??

Discussion in 'Enlarging' started by stradibarrius, Feb 18, 2009.

  1. stradibarrius

    stradibarrius Member

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    I am about to try to print my very first B&W print. I am using Ilford Ilfospeed RC Deluxe #2 grade paper.

    I am going to develop it in Dektol.
    First I am going to make a test strip but I am wonder approximately how long the expose the paper with the enlarger. I know the test strip will help me get it closer, but where do I start...1 min...45 sec...???
     
  2. Vaughn

    Vaughn Subscriber

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    I try to aim for around 20 seconds. Long enough to do any dodging and not too long for burning. The other consideration is trying to use the middle f/stops of the enlarging lens to keep the image as sharp as possible.

    Have fun!

    Vaughn
     
  3. Fred Aspen

    Fred Aspen Member

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    I usually start with an aperture of f11 and use an expired sheet of paper to do 5 sec for six intervals. You should find a reasonable exposure somewhere in that area. If not, the neg may be too dense or too thin.

    -Fred
     
  4. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Try the following:

    Take a half-sheet of photographic paper and place it in the important part of the photograph. Close the lens down 3 stops.

    1. Make a 5 second exposure;
    2. Cover up about a quarter of the paper with a sheet of cardboard and make another 5 second exposure;
    3. Move the cardboard to cover half the sheet and make a 10 second exposure;
    4. Move the cardboard to cover three quarters of the sheet and make a 20 second exposure.

    This will give you a set of exposures at 1 stop intervals from 5 seconds to 40 seconds - ie 5, 10, 20 & 40 seconds.

    If the whole sheet is too light then open up the lens 2 stops and make a series at 10, 10, 20, 40 second intervals for total times of 10, 20, 40, 80 seconds.

    If the whole sheet is too dark then close down the lens 2 stops and make a series at 2, 2, 4, 8 second intervals for total times of 2, 4, 8, 16 seconds.

    Either pick the best strip or make a new strip at some reasonable time intervals around your best guess. If, say, it looks like the best exposure is between 20 and 40 seconds then expose the paper for 20 seconds and cover it up by fifths making additional exposures of 5 seconds each, giving you exposures at 20, 25, 30, 35 and 40 seconds.

    There is no particularly wrong way to make test strips.

    You may want to adjust the aperture on the lens so your printing time is between 10 and 30 seconds. The best performance from your lens will generally be between 2 and 4 stops closed down from full open. If you have a very good lens the best performance may be at only 1 stop closed down. Aperture and time can be a trade off - for very small prints where there is a lot of light there isn't much harm from stopping the lens down 4 to 6 stops to get a reasonable printing time.

    The most expedient and accurate results are from making strips at equal fractional-stop intervals. f-Stop timers have a feature that generates the correct times for making such test strips automatically.
     
    Last edited by a moderator: Feb 18, 2009
  5. jmxphoto

    jmxphoto Member

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    Am I the only one using a projection print scale?
    http://www.freestylephoto.biz/41621-Delta-Projection-Print-Scale

    Pick an F top (usually F11 here), slap that on the spot you're most concerned about, or just smack in the middle, and pop the timer on for a min. When it's processed you can read the correct exposure time off the wedge you like the best. I've even used it to split grade. Seems to work for me so far.
     
  6. BetterSense

    BetterSense Member

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    Very interesting. So is that a transparency? It's a bit hard to tell from the photo.
     
  7. Vaughn

    Vaughn Subscriber

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    I have one of those floating around here somewhere -- but the simple test strip (using about 1/3 sheet of paper) tells me so much information that I have never felt the need to use one of the projection print scales. I suppose it is just a matter of what one is use to doing. A carefully placed test strip gives me info on exposure, contrast (over-all and local) and how much burning and dodging will be needed. But then I also always make a straight work print, too.

    Vaughn
     
  8. MattKing

    MattKing Subscriber

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    The Projection print scale is a wonderful thing. I think Kodak invented it, but like Kodachrome, they must have let the patent lapse. :smile:.

    It is hard to describe in words, but essentially it is a bunch of neutral density filters (segments) that show the result if you use an exposure time that corresponds to that segment. In other words, if you expose an image through it (for the 60 second time recommended), the segment that results in the best range of densities on your test print, will correlate with an exposure time that will give you an excellent starting point for your exposure tests.

    I think they are a much more useful aid for BetterSense, then they could ever be for someone like Vaughn, simply because they are great for getting you into the "ballpark", and, well, Vaughn is probably already in the "ballpark" anyways :smile:.

    If you cannot find one, BetterSense, send me a pm - I may have a couple extra of these, which you could have for postage.

    Matt
     
  9. Shangheye

    Shangheye Member

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    The method I have started using recently (Can't remember where I picked it up) was a piece of genius and transformed my test strips effectively in to "stops" of light for each part of of the strip. This meant I could think of modifications to expsoures in terms of stops of light just like a camera.

    Take the strip and place onnthe easel and expose all of it to the negative for 2 seconds. Then cover up a small part of the strip and expose for another two seconds. Cover up a little more of the strip and expose the uncovered part for 4 seconds, cover up more of the strip and expose the uncovered part for another 8 seconds. cover more and expose for 16 seconds etc...

    What you end up with is a test strip which is exposed as 2,4,8,16,32,64,128 etc....you can take it as far as you think your negative needs it. If you think your chosen strip is half a stop too dark then you can take half a stop off. Voila!

    The pain is that you need to keep changing the timer, but I have found it saves me more paper and time since it covers a wider range of exposures and allows me to judge what is needed from a dodging/burnig point of view.

    Rgds, Kal
     
  10. Vaughn

    Vaughn Subscriber

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    You have me confused, Kal (Matt was right I am in the ballpark -- usually way out in left field...LOL!). But following your instructions, it seems like I would get strips of 2-6-14-30-62-126, etc. I must have missed something, since it works for you.

    It seems like it would be easier to set the timer to 20 seconds (or whatever time one likes to work with) with the lens closed down to the smallest aperature, and then expose each strip separately, opening up the lens one stop each time...if one wanted each step to be one stop apart.

    Vaughn
     
  11. Shangheye

    Shangheye Member

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    Hi Vaughan...you missed out the second 2s exposure in your calculation....i.e. the second strip only got four seconds (the intial 2s for the whole sheet plus another 2s), the 3rd strip got those 4 sec0nds plus another 4seconds...i.e. 8 etc., the fourth strip got those 8seconds plus another 8seconds...i.e. 16secs.etc.

    Rgds, K
     
  12. Shangheye

    Shangheye Member

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    Just saw your second comment on your post Vaughan. The use of the aperture on the lens would not work, since it would not be a cumulative effect for the overall exposure of the exposed parts...i.e. you would ned to make sure each strip is exposed while protecting the rest of the paper. It would also need you to recalculate the exposure times, since generally you print at a selected aperture...at least that is waht I think...Will go off and see if I am correct now! Rgds, K
     
  13. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    It will work. For one stop series the exposures are 1x, 1x, 2x, 4x ...

    It doesn't matter how each exposure is doubled: it can be either time or light intensity.

    The aperture method is easier if you are working at one stop intervals. The problem is that a 1 stop interval is 2 zones on normal #2 paper, more on higher contrast paper.

    You will usually end up having to make a fine test strip with a timer after a one-stop series.

    The one stop series can be useful for judging dodges and burns which are often in the 1/2 to 2 stop range.
     
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  15. DWThomas

    DWThomas Subscriber

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    I own one of the venerable Kodak Projection Print Scales. It's excellent for a first shot, especially if trying a new paper. After that I can generally operate with small test strips in important areas and "informed guessing" to refine the exposure.

    DaveT
     
  16. Vaughn

    Vaughn Subscriber

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    Thanks! I should not try to do simple math nor try to follow simple instructions when I am up all night printing!

    Vaughn
     
  17. Chan Tran

    Chan Tran Member

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    Let me recap a bit.
    1. Using the Projection Print Scales is most convienient. You only have to expose just one time and the steps spacing is good.
    2. The aperture method works fine and doesn't need to do much calculations. You can get good steps spacing this way. You do need a way to expose just one strip at a time like the test strip printer.
    3. Using just a piece of card board and varying the time works better if the you do it by first expose the entire sheet and then cover 1 strip and 2 strip and so on. If you do it by uncovering 1 strip and then 2 strips and so on it doesn't work as well. The timing should be increased as a percentage of the last step. For example double for 1 stop steps, 1.4 times for 1/2 stop steps etc..
    4. The spacing of 1 stop per step is a bit much in my opinion as 1 stop even with grade 2 paper would change the print density about 0.50 and that's too much. I think a 1/2 stop steps are better.
     
  18. DannL

    DannL Member

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    Why is it important to think in terms of stops at the enlarger? How will that benefit me?

    I guess I can't see the advantage to the test strip method that Kal has described (I'm feeling dense today). If I determined that a 36 second exposure is too weak, a 38 second exposure is too dark, and a 37.5 second exposure would be just right, how can I discern information this accurate using the method Kal has described? When dodging, burning, or creating straight prints, I find a second of exposure here, and a second of exposure there to be quite critical to the final print. In Kal's method for example, there would be 32 seconds of exposure time residing between the 32-second and 64-second exposures on the test strip.
     
  19. Chan Tran

    Chan Tran Member

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    The reason to think in term of stops because the effects are equal. Increase of decrease exposure by 1 stop produces the same effect while increase of decrease exposure by 1 sec doesn't. If your original exposure is 1 sec and you increase 1 sec and make it 2 sec the effect is quite great. If the original exposure is 30 sec and you increase by 1 sec to 31 sec I don't think you can see any change at all. You don't have to make the steps 1 stop apart, you can make it 1/2, 1/3, 1/5 etc.. depending how closely you want them to be.
    In your example increasing exposure from 32 to 64 sec has the same effect as increasing from 5 to 10 sec.
     
  20. DannL

    DannL Member

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    32 seconds of exposure has the same effect as 5 seconds of exposure ????

    :D
     
  21. MattKing

    MattKing Subscriber

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    It's the change in exposure that counts, and it is logarithmic.

    Take an example. You have a negative that you like, and a pleasing 8x10 print results from an 8 second exposure.

    You decide to print it big - 16x20. Everything being equal, a 32 second exposure at the same aperture will yield similar tones in the bigger print.

    Now, you decide you want to try it darker, for a more moody effect. You experiment a bit, and decide that the 8x10 dark version looks best with one stop more exposure - 16 seconds (an increase of 8 seconds). If you want the same result on the big print, you don't increase that exposure by 8 seconds - instead you increase that exposure by 32 seconds, to get the same one stop increase in density.

    Now the numbers here are simplified, and there are other real-life issues to contend with (reciprocity, shift in contrast, etc.) but basically this works.

    Matt
     
  22. Shangheye

    Shangheye Member

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    I should have been clearer in my post that the full stops help me since in most cases, I find that I need to know how many more (or less) stops are needed to achieve the required burning and dodging. You can certainly run the exposures on half stops etc, or save that for your second strip (Which I sometimes do to get the spot on exposure or compare two halves of the strip at different grades etc).

    You can also buy timers that work based on f-stops rather than absolute time. Don't have one, but I can imagine how much simpler my life would be :D
     
  23. edtbjon

    edtbjon Member

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    The original purpose of this thread is to get the OP started with his printing. But going down the track he will eventually come to where you're at.
    As others have said, the benefit of making test (strips) with log changes (2,4,8,16, ...) is so that there is equal difference in exposure between the tests. You work in the same way as with your camera.
    So, for starters, making a test strip in full stop decrements is a start. Then when in the ballpark, i.e. somewhere at an exposure time or in between two of them, you can finetune in increasingly smaller decrements.
    As someone notes, there are programmable exposure timers, with which you work with the concept of stops instead of seconds. These timers (R H Design and Darkroom Automation.) can be set down to 1/24 of a stop, which should befine-grained enough. (If you miss your half-second, you can always let your hand pass under the lens...)

    //Björn
     
  24. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    That's about 1/50th of a stop difference.

    Just for grins - the effect of a 1 second change in exposure:

    Base
    Seconds --- difference in stops for adding one more second

    1.0 -------- 1.00
    2.0 -------- 0.58
    4.0 -------- 0.32
    8.0 -------- 0.17
    16. -------- 0.09
    32. -------- 0.04
    64. -------- 0.02

    Information for converting stops<->seconds is available here, and at other locations on the web.

    http://www.darkroomautomation.com/support/stopstable.pdf
    http://www.darkroomautomation.com/support/grastops.pdf
     
  25. viridari

    viridari Member

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    I referred back to this thread last night when I was getting started with my new-to-me Beseler 23C II and got some very different results. I'm wondering what I might be doing wrong.

    After doing a series of test strips with a single image, I got to where the correct exposure was 2s @ f11. The other prints I made last night were mostly 1-2s, some under 1s. I don't know if this enlarger uses an unusually bright bulb or what the deal is. Any suggestions as to what might be different with my setup that's not giving me 20-30s to work with? Is there an assumption of filters being used or something?
     
  26. Noble

    Noble Member

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    How big are your prints? My Beseler 23C III is bright. My 8x10 exposures with contrast filters are longer than that but they are still in the single digits. I was thinking of getting a neutral density filter.