What is an average exposure time?

Discussion in 'Enlarging' started by MikeS, Aug 25, 2005.

  1. MikeS

    MikeS Member

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    Hi All.

    I mostly shoot 4x5, but also do some 6x7 roll film. I've been using an Elwood 5x7 enlarger, and it has a really large 300w bulb in it. I just got an old Omega DII which has a much smaller more 'normal' enlarging bulb in it. I thought my exposure times would go up, but they are about the same. So here's my question:

    What is an average exposure time when enlarging a 4x5 to an 8x10 print? I'm curious, because using Freestyle's older EDU graded #2 paper I have a 5 second exposure at f16! I vaguely remember normal exposure times being much longer, along the lines of 15 to 25 seconds, with the lens only stopped down to like f8 or so back years ago, which left plenty of time for dodging & burning, something a 5 second exposure doesn't do! When I use Kodak KodabromeII my exposures are even shorter!

    Do my exposure times sound right? Thanks!

    -Mike
     
  2. Nick Zentena

    Nick Zentena Member

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    5 seconds at F/16 sounds real short to me.

    Depending on the condition of the Elwood I'd expect the Omega to be more efficient. It's condensors should focus light better then the Elwood.
     
  3. PeterDendrinos

    PeterDendrinos Member

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    Mike I aim to keep my times around 15 to 20seconds. I’ll let it go out to perhaps 45 before I change the aperture. My lens is most uniform at about f11.

    I would think your “average” times would depend on filter pack used for contrast control, type of paper used, density of negative, and the obvious light intensity, enlarger design, etc.

    I would simply try to get a time that allows you to do the manipulations you need to. Like I said I like the 15 to 20 zone.

    Pete
     
  4. Paul Sorensen

    Paul Sorensen Member

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    Perhaps someone smarter than me can comment on this, but for some reason I think that an 8X10 from a 4X5 should have a shorter time with the same enlarger than a 8X10 from 35mm or MF. My reasoning is that a set amount of light energy hits each square inch of the negative and that should be about the same for any size film. Therefore, the 8X10 is only 4 times bigger than the 4X5 negative while it is much, much larger than the 35mm negative. Does this make sense? The times you remember, were they with 4X5 negs and 8X10 prints?

    Just an idea, it may be really stupid.
     
  5. Konical

    Konical Subscriber

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    Good Evening, Mike,

    Paul (above) seems to be on target. Using my Beseler MCR-X, an 8 x 10 from 4 x 5 takes a rather short exposure, while an 8 x 10 from 35mm definitely takes a good deal longer, given a constant lens aperture.

    Konical
     
  6. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I'm generally shooting for a base exposure time, not counting dodging and burning, of around 20-30 sec., unless it's for those darn APUG postcards, when I'll try to keep it around 5 sec. You can always add an ND filter to the lens or an ND lighting gel over the condensors to get a longer time at a more optimal aperture for the lens you're using.
     
  7. Donald Qualls

    Donald Qualls Member

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    Other factors equal (same paper, same negative density, same lens opening), your exposure is determined by magnification if you have a cold light or diffusion -- these systems put a constant surface brightness behind the negative, so how much you enlarge is the primary variable.

    With my cold light, I find I can print 6x4.5 onto 8x10 (extremely close to full frame from the 42x56 mm actual image) in about 25 seconds with each of my two split filters at f/18; times are similar with 35 mm to 8x10 (minimal crop) at f/8, and not far off with Minolta 16 to 5x7 at f/5.6 (the Minolta, however, is printed from an Enlahead which has its own condenser, and might vary with how far the Enlahead is placed from the cold light diffuser). That's a nice time; gives some time to dodge during each exposure, if needed, and doesn't take too much extra time for burning if that's required. Your time with a single filter will likely be comparable to one of my two exposures.
     
  8. Neal

    Neal Subscriber

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    Dear Mike,

    My Omega has high and low ranges and I have to use the low range to get the time to about 20 seconds or so when printing in the situation you mentioned. I don't know anything about your enlarger, but the "low" range on the Omega is just a plate with some holes in it to block the light from entering the mixing chamber.

    Neal Wydra