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  1. #1
    Denis P.'s Avatar
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    DIY "step wedge"/"projection print scale"?

    ... how to go about it?

    I'd like to make my own version of the Kodak Print projection scale - you know, that transparency/film with a circle (like a "pie chart"), which you put onto paper, then expose for a full minute, and the segments show how long the exposure should be.... Just for fun, I don't expect spectacular results, like doing away with test strips

    I thought about printing something on an inkjet printer on transparency material, but got a better idea from a friend who works in graphics industry, and works with professional printers, where they regularly print stuff like that, so he offered to get one printed "professionally"

    You might ask why not just purchase one on eboy, but with the recent changes in Customs policies here, it's getting quite expensive to buy even worthless trinkets, as long as they are coming from abroad, so it's not an economical solution. And, since I can get one printed professionally (for free), I say, why not give it a try?

    Now, my problem is how to prepare the "pie chart" in a graphics program. I've seen the Kodak print scale in several ebay auctions, and I don't think that the scale is linear - it has ten segments, numbered from 2 to 48 (seconds), with varying opacity. Now, I'm a total idiot when it comes to sensitometry, densitometry, etc., but I don't think that the scale should be linear (i.e. opacity should not progress in 10% opacity steps, but it should be analog to f-stop values, right?). I.e. each next wedge should halve the amount of light passing through...

    So, in short - if anyone has an idea on how to reproduce this "print projection scale" in a graphics program, I'd be more than grateful. I was thinking about ten wedges, just like the original Kodak one.

    Any ideas?

    TIA,

    Denis

  2. #2

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    Johns idea was rather good and simple I would say.

    Basically, you just need to make a density series increasing in density by say 0.5 stops (0.15 D I thnk) each section.
    Your challange would be to hit equal Density increments for all the sectors, neutral in tone and sensitometric effect.

    I think John's original used a 60 seconds exposure, which translated into 2,3,4,6,8,12,16,24,32,48 seconds of actual exposure... meaning that the 2 second exposure section reduced the exposure from 60..to what? something under 5 stops? I think so. Therefore since 5 x 0.3 D = 1.5D I guess that would mean the 2 second area was equall to a Density of about 1.5; subtract 0.15 from there to get each subsequent sector.

    Also it is nice to have black on clear sector numbers so you will know what you are looking at.

    I guess you could forget all the calculations and just go for broke. Try it and figure out the value of each SHOULD USE exposure for the one really used in the test.

    Hummmm...
    I have a few newish? ideas I would like to try if your friend can make accurate, finely-tuned density controlls and would be willing to take on some more free work...
    (Now where did that smiley face go?)
    Last edited by Ray Rogers; 04-23-2008 at 04:56 AM. Click to view previous post history.

  3. #3

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    why? what's wrong with test strips? why make make it unnecessarily technical?

  4. #4
    Denis P.'s Avatar
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    Quote Originally Posted by Ray Heath View Post
    why? what's wrong with test strips? why make make it unnecessarily technical?
    Ray, indulge me...
    Nothing wrong with test strips, I'm just fooling around... trying to cut some corners, if possible.

    Besides, I'm suddently and unexpectedly stumped with some math... and being stubborn as I am, I won't let it pass.

  5. #5

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    Quote Originally Posted by Ray Heath View Post
    why? what's wrong with test strips? why make make it unnecessarily technical?
    Actually, this is a test strip of sorts.

    I do not currently use this aid myself,
    but I have used it and it works pretty well.

    As you will notice, however, there is still room for fine-tuning... so in a sense, you are right... there is not much advantage over conventional test strips, of which there are several.

    I guess it is rather easier to give one exposure at one F/stop value to get 10 different test results than it is to keep changing/moving something or other to get the same results... in addition to reducing the possibility of a goof-up somewhere along the line.

    Also,
    Perhaps the shape of the sectors (triangular, slice of pie type) is more suited to certain subjects than others.

    Ray

  6. #6
    Jim Jones's Avatar
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    Even if you lay out the design in a graphics program, film may not have a linear enough response to make an accurate scale. Of course you could always assign arbitrary numbers or letters to each segment and determine the exposures by testing.

  7. #7
    Bobby Ironsights's Avatar
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    I have an exposure scale, projection print wedge, whatever.

    It wasn't homemade, it was made by kodak.

    It sucks,

    Why make one at home?

  8. #8

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    I have a Stouffer step wedge and it's very helpful.

    I've contact-printed it on each paper I use using the same enlarger height, lens, aperture, etc. The resulting print-scale shows me the differences in paper speed, length of contrast scale and what adjustments are needed in exposure time and/or aperture when changing grades.

    It helps you to know the characteristics of your material and is a useful reference in the darkroom.

  9. #9

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    It's a joke to take seriously!

    Quote Originally Posted by Bobby Ironsights View Post
    I have an exposure scale, projection print wedge, whatever.

    It wasn't homemade, it was made by kodak.

    It sucks,

    Why make one at home?
    Yea, that DIY route is not always the way to go!
    I know a guy who went to a museum once and saw some paintings.
    They really impressed him a lot, so much so that soon thereafter, he enrolled in painting class.
    Today I saw his work.
    It sucks.

    Same thing I guess.

  10. #10
    Denis P.'s Avatar
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    Well, despite all the naysaysers, I went ahead with this project.

    With the help of a friend, I devised a step wedge of a kind - well, more like a pie chart - my take on the "Kodak Print Scale". It has 10 segments, which I made by increasing density by 10% for each segment (more or less)...

    The increments are in 2, 5, 10, 20, 30, 50, 65, 80, 90 and 95 percent of black...

    The pie chart was printed on graphics film in a printing house (done professionally!), and today I did some tests. My time calculations are pretty close, and I did some test, exposing the pie chart for 20 and 30 seconds.
    The segments came pretty close to actual test strips.
    Another possible use is similar to what PVia above does - use it as a variant of Stouffer step wedge, to determine speed and characteristics of different papers...

    In short, interesting exercise (in futility, perhaps, but still interesting...).

    Could come in handy. The way I do test strips is rather slow - this might speed thing us just a litlle bit.

    Attached is a PDF variant - it will make the concept easier to understand for visual types like myself

    Denis
    Attached Files

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