Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,502   Posts: 1,543,414   Online: 777
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 16
  1. #1
    Palantiri7's Avatar
    Join Date
    Jan 2006
    Shooter
    Large Format
    Posts
    127

    Pentax digital spotmeter index numbers

    Hi everyone,

    My Gossen Starlite lightmeter died in a heavy downpour yesterday and I just purchased a Pentax digital spotmeter to replace it. After reading the manual online I observed that there is a table in there advising the user to adjust the index number based on the reflectance of the colour being measured. According to the manual, yellow has the highest reflectance and thus should be placed at '8' on the index number scale: leaving it at the standard index would result in underexposure. For purple and indigo colours the index should be set for 2 or 3. I wanted to know if anybody actually does this as I have not seen it mentioned in any thread that I looked through. I will be using the meter for Velvia as well as for b&w film exposures. Thank you everybody!

  2. #2

    Join Date
    Dec 2005
    Location
    Tempe, AZ
    Shooter
    Multi Format
    Posts
    302
    I hope we hear from someone who understands this I take it that yellow should be placed 3 stops off of Zone V, not on "8" on the index number scale, so you should close down three stops from a reading on yellow... But not sure this is what they are saying.

  3. #3
    Palantiri7's Avatar
    Join Date
    Jan 2006
    Shooter
    Large Format
    Posts
    127
    Thanks SW. I clearly don't understand! I know my Rollei 6003 meter used to overexpose blues slightly and underexpose reds so I don't know if that's the same thing here. Out of all the posts I've read about the Pentax (a lot!) I've never read anyone making mention of oddities in the meter's readings w.r.t. colour.

  4. #4
    Greg Davis's Avatar
    Join Date
    Feb 2004
    Location
    Crestview Hills, KY
    Shooter
    8x10 Format
    Posts
    1,920
    Looking at the page in the manual you are reading, it appears they recommend setting your EV value that you read inside the viewfinder on "8" according to the very bottom scale, the one labeled "IRE" when reading a yellow object rather than on the big orange arrow that we normally use. That arrow is set at 3.5 on the "IRE" scale. All I can say is shoot a few test exposures using your normal method and the method described in the manual and see what you get.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  5. #5
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,532
    Images
    1
    Quote Originally Posted by Palantiri7 View Post
    ...I wanted to know if anybody actually does this as I have not seen it mentioned in any thread that I looked through...
    I've never worried about subject colors or the meter's spectral sensitivity. Anyway, since Pentax does not know what film I'm using, or how I alter its spectral sensitivity through filtration, how could they possibly offer advise.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  6. #6
    Palantiri7's Avatar
    Join Date
    Jan 2006
    Shooter
    Large Format
    Posts
    127
    Thanks for the answers guys. I will test it out with some film when the meter gets here.

  7. #7

    Join Date
    Jul 2007
    Location
    Netherlands
    Shooter
    Medium Format
    Posts
    5,686
    Different colours do reflect different amounts of light.
    Just ignore the colour for a moment, and think of them as grey cards with different reflective properties. Or look at B&W pictures (they, after all, ignore colour too) and see how tones of parts of the subject differ though shot in the same light, depending on what colour they were.

    So you do need to worry about colour when using a spot meter.
    It's one the many 'joys' of reflected light metering.

    Grassy green is close to 'middle grey'. So if grass or leaves are available, take a reading off them and you don't need to correct.

  8. #8
    Dan Henderson's Avatar
    Join Date
    Feb 2005
    Location
    Blue Ridge, Virginia, USA
    Shooter
    4x5 Format
    Posts
    1,891
    Images
    241
    I have used a Pentax digital spot meter for years. I almost always measure the important shadow area of the scene and place it on Zone III to decide on the exposure, and measure an important highlight to assess the brightness range. I have one of Ralph Lambrecht's zone stickers covering the scale, so the orange triangle and other markings are covered. I never did know what the others were for anyway. My shadows are always properly exposed unless I make a significant error in translating the settings to the shutter.


    web site: Dan Henderson, Photographer.com

    blog: https://danhendersonphotographer.wordpress.com/

    I am not anti-digital. I am pro-film.

  9. #9
    Palantiri7's Avatar
    Join Date
    Jan 2006
    Shooter
    Large Format
    Posts
    127
    Thanks, Dan. Frances Schultz/Roger Hicks had an explanation about the IRE scale in "Medium format and large format photography". Apparently the "1" on the IRE scale corresponds to 2.667 stops underexposure w.r.t. the metered reading and the '10' represents 2.3333 stops overexposure w.r.t. the metered reading. For negative film they meter a shadow and place the EV reading against "1" on the IRE scale.

  10. #10

    Join Date
    Sep 2002
    Location
    Oregon and Austria
    Shooter
    4x5 Format
    Posts
    833
    As I understand it, the IRE scale was developed as a kind of "Zone System" for television cameras, with the "1" being the lowest practical value and the "10" being the highest (100% signal). Placing colors for TV/video exposure higher or lower on the scale in order to correspond to the absolute reflectivity is exactly what we film photographers do when we "place" a color on our Zone System Dial (thanks Ralph!). Pentax's suggestions about where certain colors "fall" on the scale is the same as visualizing that, say, bright yellow, falls on Zone VII (or VIII if you like...). Pentax is just doing the thinking for you.

    Although the IRE scale can be used as a kind of Zone System for film photography, it seems a lot more fiddley and less linear than the classic Zone System or any of the newer systems based on sensitometry for B&W films. Rory's post above, however, seems to indicate that the scale might be very useful for slide films... I don't know.

    Bottom line: If you shoot B&W don't worry about the IRE scale unless you need to meter for video cameras. If you use the Zone System, get a Zone Dial and tape it over the IRE scale :-)

    Best,

    Doremus Scudder
    www.DoremusScudder.com

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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