Focusing when you can't see...

Discussion in 'Canon EOS' started by b.j._porter, Sep 17, 2005.

  1. Had an...interesting assignment today.

    It involved photographing a drill where a local fire department suited
    up the City Council into full fire fighting gear and sent them into a
    fire training building in drill conditions. Low to no light, smoke
    (artificial non toxic), etc.

    The inside of the building was dark, and they had an artificial smoke
    generator going to simulate the really smokey conditions in a real
    fire. Except for the smell of it and the lack poisonous fumes it was
    pretty eerie and realistic. Following a veteran fireman around the
    basement looking for a place with enough dim light to shoot HE got
    disoriented.

    Anyway, I was trying to get pictures inside. I set up near the
    doorway where there was SOME light and much less smoke, you could see
    dimly. My intent was to try and get hazy dimly lit figures as they
    emerged through the somke with flashlights, etc. Using a 20D set on
    ISO 3200 with a 50mm F1.8 lens on a tripod.

    I didn't want to try any flash shots, because I figured they with the
    smoke and haze I would get lots of nice pictures of polar bears in
    blizzards.

    The problem was that with the low light and the smoke, autofocus
    didn't work at all, and my eyes couldn't focus all that well
    either...and I was not able to determine throug the viewfinder if the
    door I had pre-focused on either.

    So, there WAS sufficient light to get pictures especially when people
    had flashlights and so forth, but as I am finding now while reviewing
    the shots I have major focus issues.

    Any thoughts on how, going forward in a situation like this you can
    have a ghost of a chance on getting an in focus image? I couldn;t
    read the focus marks on the lens too well by flashlight either...

    Of course, my issues were exacerbated by the annoying TV camera guys
    coming through with their lights from time to time...
     
  2. SCL

    SCL

    The same thing rangefinder photogs have been doing since the 1920s...prefocus the estimated distance and wait for the action to come into range. Many dramatic firefighting photos have been taken this way. One which really hit the papers big was in the 1950s of a fireman carrying a child out of the "our Lady of the Angels" fire in Chicago.
     
  3. Yup, scale focus. Easier to have an accurate idea what you're doing with an old manual
    focus lens (and easier to see the scale when it's not in some little window). Leica, Nikon
    and Contax all have good focusing scales. Pick up an adapter and a couple of wideish
    primes and you're set.

    If you really can't see even good lens markings you'll just have to pick a distance before
    going in and be very careful not to bump the dial.
     
  4. Something you may want to try (not sure if it will work in the smoke, but worth a try) is using a Canon Speedlite. You could possibly prefocus using the infared emitter of the flash then turn the flash off and the lens to manual focus. Or set C-FN-04 to 1 then you would not have to turn AF off on the lens after you prefocus, just turn off the flash.
     
  5. The MK II version of the 50 1.8 has no MF distance scale, so if that was the version you were using than that wouldn't have even been an option...
     
  6. I am visiting from the Nikon forum. Excuse my lack of familiarity with Canons.

    You could affix a light trigger by the door so that when the light beam was broken by the people, your shutter would snap. You could program in a slight delay, if needed for subject positioning. Because of the smoke, you would set it to be insensitive to the smoke. Sort of like calibrating a smoke detector. Some use a broken beam of light and you can adjust the sensitivity. Nature photographers use this type of arrangement to shoot bats, birds, nocturnal animals, and other stuff they cannot see.

    Secondly, maybe your Canon has a mode whereby you can focus on a spot and when a subject enters that area of focus, the shutter releases. Sports photographers would use this finish lines at race tracks, football games, etc.

    Maybe you could prefocus and then enhance your ability to see through the smoke by wearing heat-sensing goggles, or night vision goggles that multiply the light. You may not be able to use those for any purpose except to know when to release the pre-focused shutter.

    You can focus by scale to capture more than one prefocus place. Place a handle on the focus ring. Mark 2 or 3 distances on it by braille-type markings. 1 drop nail polish, 2 adjacent drops, etc. I actually had a similar situation a long time ago. Shot a friend's wedding. Too dark to focus a Hasselblad inside the buildings. Panic! Used the Hasselblad focusing ring. One marker for couple shots. Another for groups of 3-4 people. Another for 6 or so. If the right number of people filled the dim viewfinder, I know where to turn the handle to. I stopped way down and used a big flash. All was OK.

    Sounds like a fun assignment.

    Bill
     
  7. Either manual focus (and shot TONS of brackets) or maybe a flash set up in the corner in the room on a cord.

    My personal favorite would have been a 45-point autofocus. Better than the 11-point of the 20D.
     
  8. Hyperfocal
     
  9. I personally think that DON W suggestion is probably the best thing to do. Not just because it is a good idea, but because I tried it and it works perfectly.
     
  10. Decide on a working subject distance before you enter and prefocus the camera. Put it in MF mode and tape the focus ring in place. You don't need a distance scale. If you decide the 3 meters is going to be your distance then stand 3 meters from a person and focus on them before you enter tape the focus ring in place so you can't knock it. Best not to try and shoot wide open though as the more DOF you have the easier it will be.
     
  11. >>I am visiting from the Nikon forum<<

    Oh no...a saboteur spy! ;p
     
  12. You MUST use manual focus and anticipate around f/5.6 in that case, plus you were using the wrong lens. The 50mm 1.4 would have been much better as would any wide angle zoom.
     
  13. Just spy, Giampi, not saboteur spy. After visiting many forums, including Nikon-oriented ones, I can resolutely say that sabotage is not necessary in photography. Self-destruction by the target groups obviates the need for outsider-based actions. :)

    Bill
     

Share This Page