More darkroom/enlarger advice

Discussion in 'UK Photography' started by Paul Giverin, Jul 31, 2009.

  1. Paul Giverin

    Paul Giverin Guest

    Well, project darkroom (in my shed) is nearing completion. Thanks to
    everyone for putting up with my frequent questions.

    I've now got just about everything I need. Most of the kit and all of
    the chemicals. I could do with a timer but I hope to have one within the

    I've developed my first roll of film. It was a roll of Agfa APX 100 and
    I used Rodinal to develop it. As far as I can tell it seems to have come
    out fine.

    Now I've got to have a go at printing some of the shots. I've got a
    Durst M370 enlarger with Nikor F4 lens and I had a dry run with it the
    other night. I had bought a focus finder but didn't know how to use it
    but eventually figured out that I was looking at the grain and not the
    image itself.

    What I need help with is exposure times. I assume that I should be
    exposing at F22 for greater control? What time should I be exposing for
    initially? I understand that I should do a test print using a bit of
    card to incrementally mask off the print at various times and check to
    see what strip gives the best result but what time should I start off
    with? I'm using 8"x10" paper.

    Also, what is the red filter below the lens for? I know that filters can
    be fitted in a holder above the lens for altering the contrast but I
    don't know what the lower filter is for.

    Is the temperature of the developer as important as it is when
    developing film?

    That's all for now, thanks.
    Paul Giverin, Jul 31, 2009
    1. Advertisements

  2. For good control it's better to use a timer that is plumbed into the
    enlarger which turns the light on for a precise number of seconds. That way
    even exposures of 1 sec are no problem. If the enlarger doesn't have its
    own timer, you can get generic ones which sit between the equipment and the
    mains supply. Aperture-wise, I would tend to go for about two stops down
    from open aperture (f/8 in this case) for optimum image quality. Exposure
    depends on many things like brightness of lamp and degree of enlargement
    (inverse square law applies) so you just have to experiment. But it will
    probably be somewhere between 1 and 60 seconds!
    It just acts as a safelight whilst composing the image with paper in place
    on the easel, however these things tend not to be very "safe" in practice
    and most people remove the filter + stalk since they just get in the way.
    The fact is that there is almost never any need to have the enlarger light
    on when the paper is in position (assuming you are using a masking frame),
    (except during the exposure itself of course).
    Marty Freeman, Aug 1, 2009
    1. Advertisements

  3. Exactly right! They are (were) sometimes known as grain focus finders.
    The cheaper ones with rear-surfaced mirrors are not always spot-on
    though; a good front-surfaced one will astonish you by its cost (mine
    was over £100 back in the 90s), but also by its superiority.
    No! As Marty advised, go for an aperture a couple of stops down from
    wide open. The reason for this is that maximum resolution will be
    severely reduced by using f/22, by a phenomenon known as diffraction*.
    The exposure time for the paper should always be at least that required
    to give a true black on the areas of film which received no detectable
    exposure. Otherwise, you will get no true blacks in your print and they
    will look grey and muddy. As Trev said, you must also develop for the
    full time recommended by the paper maker, or you will also get "grey"
    prints. (In practice, overshooting by a few percent is not going to have
    a noticeable effect as most modern RC paper in effect develops out to
    completion, though if you leave it to stew too long it will start to

    There are also several other calibration tests you should do to get the
    best print - see the book recommendation in the last para below for
    As Marty says, remove it; not only will it quite probably not be "safe"
    for a variable contrast paper, it will affect the focus accuracy of your
    focus finder. You should always focus on a piece of blank paper the same
    thickness as your printing paper, and in the same light as will be used
    for the exposure.
    As Trev said, consistency is the most important thing; if you have done
    tests to find the minimum exposure time, they will be wrong if you
    change the temperature. If the temperature drops, developing time will
    extend, and if you go too low, you risk the development not going to

    *A footnote on resolution. (This may be far more detail than you wanted,
    which is why I put it in a footnote.) The "sharpness" of a print depends
    on many things, the sharpness of the camera lens, of the film, of the
    enlarger lens, of your focusing accuracy, and the paper. Roughly, total
    resolution = (1/R1^2+1/R2^2+1/R3^2+1/R4^2...)^-0.5, where R1, R2... are
    the resolutions of the various stages.

    The resolution of the enlarger lens is approximately 1500/Effective
    Aperture, where Effective Aperture (of the enlarging lens) is Marked
    Aperture*(1+Enlarging Magnification). Thus for a print at 10x
    magnification at f/4, R is approximately 1500/44, or about 34 lp/mm in
    the print. For the same print at f/22, R is about 1500/242, or 6.2

    To put this in context, a print of 5 lp/mm will look reasonable sharp
    from a distance, but will disappoint close-up. 10 lp/mm will look pretty
    good, but for perfection you should aim for 30 lp/mm. You won't do it
    with 35mm film, but you can get credible close if you take care of all
    stages. Of course, the 34 lp/mm (or the 6.2 lp/mm) is further degraded
    by blur in the camera, the film, the paper, and of course any focus
    errors you make.

    The problem is that any lens you are likely to use will not overall give
    its best performance wide open. At this aperture, there will be
    degradation from lens aberrations, which improve on stopping down. Hence
    the best performance, for the very best of lenses, will be about 1 stop
    down; for "second rank" lenses it will be more like 2 stops. Don't know
    your lens, but I would guess it falls in the latter category, hence f/8
    would be the aperture to try. The other reason for stopping down is
    that, even if the lens gave better *resolution* at f/4 or f/5.6, it is
    likely to give lower contrast at these apertures, and it is usually
    worth sacrificing a little resolution to get better contrast.

    If you are still reading this, and find the search for perfection is a
    path you wish to follow, I recommend you read "Post Exposure" by Ctein
    (yep, that's how he spells his name). I haven't done much darkroom work
    for the last decade or so (digital....!), but when I did this was the
    book I found most useful in the quest for quality. There may be more
    recent books which are better though.

    David Littlewood, Aug 1, 2009
  4. Paul Giverin

    Paul Giverin Guest


    Finally did it last night. My darkroom (shed) still needs a bit of work
    with the door sealing so I have to wait until after 9pm. I cut some
    paper into quarters and did several test exposures as advised. Its quite
    a thrill to see your first print appear in the developing tray.

    I deliberately didn't use the film I'd developed a couple of nights ago.
    Instead I used the negs of some film that Ilford processed for me a
    while ago. I knew that the film had been processed correctly and I also
    had a copy of Ilford's print to compare against mine (albeit my prints
    were twice the size)

    I struggled to time the exposure with my digital watch. I had to hold
    the watch really close to the safelight to be able to read it and it was
    then a bit of a stretch to the enlarger switch. I will be getting a
    better timer soon.

    Looking at the results, I realised that I had made a mistake in buying
    warmtone paper. The Ilford prints looked cooler, and I prefer that look.
    One problem I had was getting the paper to sit flat under the enlarger.
    The paper had a bit of a curl and I had to use a spot of double sided
    sticky tape on the centre of the easel to try and keep it flat.

    Mistakes..... Despite having three sets of tongs, I used the same set
    throughout and ended up with tong marks on my prints. I also failed to
    realise that I should wash the prints after coming out of the fix. I
    just squeegeed them and hung them up. I didn't give them long enough to
    dry either because I wanted to show everyone in the house what I'd done

    I tried out my contact print thingy with the film that I'd previously
    developed myself and then made a full sized print from one of the negs.
    It was getting close to midnight so I had a quick tidy up, another glass
    of sauvignon blanc to celebrate and then to bed.

    I've obviously got a lot of experimenting ahead but its great fun.

    Thanks to Trev, Marty and David for your great advice.
    Paul Giverin, Aug 2, 2009
  5. Sounds like you don't have a masking frame (aka Enlarging Easel) - that's a
    pretty essential item. Apart from holding the paper flat (and ensuring it's
    in the right place on the baseboard to begin with) it gives you a frame
    into which you can compose the image and experiment with cropping by moving
    the blades. You can probably pick one up cheaply second hand somewhere.

    You can also get magnetic corners that will grip the edges of the paper if
    you want to make borderless prints.
    Marty Freeman, Aug 2, 2009
  6. Paul Giverin

    Paul Giverin Guest

    Thanks Marty. I'm using the 10x8 holder (no blades) that came with the
    enlarger. I was aware of the proper easel with the blades but I do
    prefer borderless prints. I will look into magnetic corners.

    I've just developed my second roll of film. I had shot a roll of tri-x
    400 on holiday a couple of weeks ago. I've still got a pre-paid envelope
    for developing at Ilford and was going to send it away but I decided
    that I needed the practice.

    The trouble is, the only film developer I have at the moment is the
    Rodinal and I've read that its not always ideal with tri-x. Some people
    swear by it and say it gives lots of grain, others say to avoid using
    it. Anyway, I'm up for it so I developed it for 10.5 minutes at 1:50
    concentration. I must say that the negs look different to previous tri-x
    negs that Ilford processed. I'll do a contact print tonight and see how
    it goes.

    I've just been into WarehouseExpress this morning and bought some
    cooltone papers. I really didn't like the look of the warmtone papers I
    printed last night. I've still got a lot to learn but I'm really
    enjoying it.
    Paul Giverin, Aug 2, 2009
  7. Magnetic corners are good, but there are three things to watch. First,
    they are rather too easy to move in the dark, so your paper can get
    misaligned. Second,if you are not careful a little bit of the corner can
    overlap the paper and leave a blemish (certainly the Patterson ones I
    used to use can do this) - you just have to take care here. Third, some
    papers will not lie flat even with the corners in place. My solution to
    both is to clamp two straight edges to the easel, one at the back and
    one at the side. Push the paper against both and it cannot move. Then
    use several (4 will do for smallish papers) pieces of double-sided
    sellotape stuck to the easel to ensure it doesn't bend up. You'll need
    to replace them every session otherwise they get contaminated with dust
    etc. and lose their stickiness.

    David Littlewood, Aug 2, 2009
  8. A guillotine or modelling knife and metal ruler would be better - I find it
    very hard to cut a sufficiently straight line with scissors, and even a
    fraction of a millimetre of wobble is pretty obvious unfortunately.

    OTOH if you are intending to frame a print, borders are good, since it
    gives you a better overlap when placing the print over the hole in the

    The mention of 10x8" reminds me of something that has always bugged me ever
    since I started b&w printing many year ago (please excuse off-thread

    The pre-eminence of the 10x8" paper size has always bemused and indeed
    annoyed me. 10x8 may be a perfectly fine size for people using plate
    cameras or 4x5's, but it makes no sense at all for 35mm users. A4 is a much
    more practical size being quite close to the 1x1.5 aspect ratio and of
    course is also a standard stationery size. And yet paper manufacturers
    persist in making 10x8" paper and (I don't know about now, but this used to
    be the case) may even charge a premium for a more sensible size like A4.

    When I used to run a darkroom for a photography club some years ago, we
    decided to standardise on A4 paper, but had to pay a 30% premium per square
    inch for the privilege of using a paper size which actually made some kind
    of sense for our darkroom users. However by buying 100 sheet boxes we were
    still able to procure it for members at a better price than if they had
    been forced to buy 10 sheet packets of 10x8 for themselves.

    For personal use my own solution has been to standardise on 12x16" paper.
    Cut this in half with a guillotine and you get two sheets of 12x8" which is
    perfect for 35mm and close enough to A4 to fit most folders, plastic
    wallets etc. Meanwhile for large prints, 12x16" is closer to 35mm format
    than 10x8", so you don't waste as much when printing full frame on a whole

    The only advantage I can see for 10x8 is that you can cut a strip off to
    use as a test strip, however in practice the strip will be a bit narrow for
    a decent test strip.
    Marty Freeman, Aug 2, 2009
  9. Paul Giverin

    Rob Morley Guest

    Sounds like a vacuum table would be a good idea.
    Rob Morley, Aug 3, 2009
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.