Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,760   Posts: 1,516,077   Online: 889
      
Page 3 of 3 FirstFirst 123
Results 21 to 26 of 26
  1. #21
    BetterSense's Avatar
    Join Date
    Aug 2008
    Location
    North Carolina
    Shooter
    35mm
    Posts
    2,828
    Best I can tell, the meter sensor that BetterSense used is sensitive to IR
    Indeed; I have never tried to use it as an IR meter, but when I was testing it without an IR filter, green foliage in sunlight read about 2 stops brighter than pavement, which is hardly what you expect based on visible light but is consistent with IR.
    f/22 and be there.

  2. #22
    Hexavalent's Avatar
    Join Date
    Nov 2009
    Location
    Ottawa, Ontario, Canada
    Shooter
    Multi Format
    Posts
    532
    Blog Entries
    3
    I suppose 741's are analogue enough, for the purist, a Philbrick op-amp would be better.

    In reality, a couple of discretes are all that are needed for a decent light-meter.

    and Yes, Chromium, one of my favourite metals.
    - Ian

  3. #23
    Steve Smith's Avatar
    Join Date
    May 2006
    Location
    Ryde, Isle of Wight
    Shooter
    Medium Format
    Posts
    8,530
    Images
    122
    Quote Originally Posted by Hexavalent View Post
    C'mon we're supposed to be Analog here - how about a couple 12au7's and a neon voltage reference
    That's my sort of electronics! See Valve Audio link below!


    Steve.

  4. #24

    Join Date
    Jan 2007
    Location
    Sydney, Australia
    Shooter
    Multi Format
    Posts
    301
    Images
    1
    Quote Originally Posted by BetterSense View Post
    There is no real circuit diagram; all the information is in the TSL230 datasheet. Here's a picture of two of my older meters though.
    I'm interested in how you narrowed the field of view for the spot meter (lens?, pinhole?). Does it have a viewfinder so you know what you're pointing it at?

  5. #25
    BetterSense's Avatar
    Join Date
    Aug 2008
    Location
    North Carolina
    Shooter
    35mm
    Posts
    2,828
    I just use a lens, exactly like a camera. The longer the focal length, the smaller the angle intercepted by the sensor. Brightness is controlled by F/ratio exactly like a camera, so a longer lens tends to have a worse aperture, though. Right now I'm using a coated, F/.9, 18mm lens, which is very compact, but only gets me a 4 degree spot in low light. Since my sensor can adjust its active area according to brightness, in medium (room) light, my spot size is .4 degrees and in sunlight it's theoretically .04 degrees although with flare I'm not sure that's a meaningful number.

    If I wasn't a compactness maniac I have a f/2, 50mm lens that I would use. I suppose this is similar to the lenses used on Pentax spotmeters and so on.

    Aiming is accomplished by sighting through a peephole that runs through the length of the meter, which consists of 4-5mm diameter aluminum tubing. It's a bit squinty but works well. I've considered adding some rifle sights, but they would stick out.
    f/22 and be there.

  6. #26

    Join Date
    Aug 2009
    Location
    Selah, WA
    Shooter
    Multi Format
    Posts
    254
    I've got a 50mm Nikon lens with a bad blade,,, hummm. Was looking for a broken spot meter to use as a base, with the splitter already built. How about building the thing into one of the 620 film Kodak TLR's, or even an Argus C3?

    I'll go back thru the thread and take a look at the software and PIC side now

Page 3 of 3 FirstFirst 123


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin