Ground Glass Brightness

Discussion in 'Talk About Large Format Gear' started by Ian-Barber, Aug 19, 2016.

  1. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    Today was my first outing with a 5x4 camera and the most frustrating thing I found was how dark the image appeared on the glass even under a dark cloth.

    The weather today was overcast and raining for the most part so I ventured inside the local church as i wanted to make a photograph of the tall stone pillars. In the end, I had to cancel the composition simply because I was really struggling to see the overall scene though the glass.

    This hopefully, maybe just as simple as not been used to looking through ground glass.
     
  2. Keith Haithwaite

    Keith Haithwaite Active Member Registered User

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    The bane of large format photography I'm afraid Ian but don't give up, it just takes practice, practice and more practice and you picked the worst possible conditions in which to start. Once you are under the cloth give your eyes time to adjust to the new light levels which can take several minutes and of course make sure the lens is wide open. You will soon get used to moving your point of view around the screen and building the picture in your minds eye and then gradually it will all fall into place - a bit like learning to ride a bike really.:)
     
  3. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    From the research I have been doing, you are probably right there Keith. The second exposure I made was a simple still life which I wanted to try because this is an areas of interest.

    The first 2 negatives have now been developed in HC-110 and are currently hanging up to dry.

    blowtorch_4x5.jpg

    first_4x5.jpg
     
  4. Jonathan Woods

    Jonathan Woods Member Registered User

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    What were the light readings? What's the widest aperture of the lens you were using? What ground glass (brand/make) was it? Also, what was the reproduction ratio?
     
  5. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    The metered exposure for both images was 1 second. The widest aperture of the lens is f/5.6 and the camera is a Keith Canham DLC. As for the reproduction ratio I am not quite sure but the negatives in the previous post are the two images in question.
     
  6. Jonathan Woods

    Jonathan Woods Member Registered User

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    Ahh ok, 1 second is quite dark I suppose. That said, I'm guessing that was 1 second when stopped down? What iso was the film?

    Sorry for the 20 questions, I'm just trying to get a gauge on how dark it really was by getting an idea in my head against that of some exposures I've made before. I managed on my Shen hao to compose with a loupe for a 20 second exposure stopped down at f16 at iso100. Perhaps I was just lucky at the time with bright spots in the scene that I could focus with.
     
  7. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    The film used was Ilford Delta 100. I know a church on a cloudy rainy damp day is not the ideal lighting sceneario
     
  8. Keith Haithwaite

    Keith Haithwaite Active Member Registered User

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    If you are struggling to focus in dim light Ian you can always resort to using a decent torch. Even in the church interior you can stand a torch so that it illuminates a relevant portion that will allow you to get a focus and you can always move it around to check different areas. A bit of a pain and time consuming I know but it is a tried and proven method and nobody said LF shooting was quick. ;)
     
  9. Alan9940

    Alan9940 Active Member Registered User

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    Hi Ian,

    A few other suggestions in addition to those already stated...

    1) Over all the years I've been doing LF photography, I've found that "darkcloths" seem to run from not so dark (that is, light transmits fairly easily right through the cloth) to pretty much totally black. The really dark ones I own were custom designed by me and sewn up by my wife. A good exercise is to hold your cloth up against a bright window from inside a somewhat dark room and see how much light you can see through it. Sounds odd, but you may be surprised!

    2) When viewing the gg with the cloth over your head, wrap the material around the back to eliminate as much light as possible; you don't mention if your darkcloth is the style that "attaches" around the rear standard.

    3) For darker areas, like your church interior or when shooting outside late in the day, an infrared pointer (like the ones used for presentations) works great. Some of those units throw a beam pretty far into the scene and you can focus on the point of light (akin to Keith's torch idea.)

    4) Groundglass is not all the same; some are brighter than others and you may be able to add a fresnel. Personally, I don't like a fresnel because I find the concentric rings easily visible and distracting.

    You may want to research making your own gg. It's not hard and with a sampling of various grit levels (and patience) you may be able to make one brighter than the one on your camera now. I've made a couple and have been very pleased with them.

    Hope something here helps and leads you in a direction.
     
  10. Jonathan Woods

    Jonathan Woods Member Registered User

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    Infrared? How's he going to see that? Surely you mean visible? :D
     
  11. Richard Warom

    Richard Warom Member Registered User

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    Hi Ian
    I had the same trouble with brightness and my eyes don't focus so well on a dim picture I have a Shen-Hao and purchased an Ebony ground glass and focus screen from Robert White and the improvement is immense I get a sharp bright image that even I can focus on, they are not cheap but worth the outlay and a lot cheaper than a Beatie set up, I believe they still do them but need to check size for your camera viewing screen.
     
  12. Keith Haithwaite

    Keith Haithwaite Active Member Registered User

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    I think Alan meant a laser pointer Jonathan.
     
  13. Alan9940

    Alan9940 Active Member Registered User

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    Yeah, sorry folks...had infrared on the brain yesterday! :) Keith is correct.
     
  14. Keith Haithwaite

    Keith Haithwaite Active Member Registered User

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    If you are considering making your own GG Ian let me give you food for thought having done this myself - although not for a camera GG.

    1. What you need is a piece of glass as near to the size/thickness of your existing GG as you can get.
    2. A flat sheet of glass to do the grinding on - a 12" mirror tile is ideal and I have got one you can have.
    3. Automobile valve grinding paste - coarse at one end, fine at the other - I have got that also.
    4. Possibly Autosol chrome cleaner in case you want a finer GG - I have that as well.
    5. Latex gloves so your fingers don't slide off the glass you are grinding - I have some.
    6. A big bucket of patience - you'll have to supply your own. :)

    7 Lay the mirror tile on a flat, non-slip surface - or use double-sided tape on the back to hold it down.
    8. Smear a thin layer of coarse grinding paste on your new piece of glass and then lay it carefully on the mirror.
    9 Using your fingertips on the surface, manoeuvre the new glass around until you have an even film of paste between the two surfaces and then commence random orbital motions of the new glass over all the mirror. It should not be necessary to apply pressure but if you feel you have to it must be even and very light.
    10. Carefully slide the glass off the mirror at intervals to check the grind, clean the debris off the mirror and glass and apply new paste.

    From here on it's all about patience and switching paste grades as required until you have a suitable finish. It's a matter of testing and grinding then until you are satisfied.

    Hope this helps.
     
  15. Alan9940

    Alan9940 Active Member Registered User

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    I use a 3x4" piece of 1/4" plate glass for the grinding, but I really like Keith's idea of the mirror tile! Assuming you apply even pressure across the glass, you should get a nice, even grind. I'm thinking my smaller piece of glass might produce uneven "spots", though I've made a few and never noticed any issue.

    Anyway, just thought I'd toss out another idea. Oh, and for the grinding grit I use the same stuff rock tumblers use at various levels of coarseness (is that a word?)
     
  16. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    Update:
    I have just returned from exposing 2 more negatives, this time I was outside and the screen doesn't look that bad under the dark cloth, in-fact its fairly bright so maybe, just maybe the issues before was simply down to a dark environment I was in.

    Now time to develop these to see if I get any scratches.
     
  17. Richard Warom

    Richard Warom Member Registered User

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    Thats good Ian it does take a while to get used to viewing on ground glass anyway, I wear variofocul specs and only the bottom third of them is for close focusing so sometimes use +3.50 reading glasses which gives that bit extra magnification and stops me breaking my neck trying to view the whole screen. As for the scratches I normally use Grafmatic holders and the other day unloading a DD slide I got bad scratches also, this was caused by panicking to get the film out of the holder. With LF a sense of humour definitely helps as I look back over my experiences.
     
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  18. Alan9940

    Alan9940 Active Member Registered User

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    I actually use +3.50 reading glasses for final focusing on all my LF cameras and, even my Rollei. I got used to it years ago with the 8x10; can see the entire gg clearly and keeps my hands free to set movements and such.
     
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  19. KenS

    KenS Active Member Registered User

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    Ian,

    Out of sheer curiosity...might I inquire as to your experience with that 4x5 Kodak GG I sent last year. Has it made or, does it make your focussing any 'brighter ... or easier?

    Ken
     
  20. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    If I put my Fresnel behind it, I would say its marital brighter but I am not sure if its designed to be used with a Fresnel
     

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