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  1. #1
    Join Date
    Dec 2006
    Location
    Toronto
    Posts
    155

    Minolta 50mm f1.7 - overexposure daytime

    I have taken a couple of outdoor shots on full auto and am getting over-exposure problems. Take on a 50mm f1.7 lens:



    Auto exposure: F/5 1/125 sec ISO-100, M=pattern metering, 0 step exposure compensation.


    What setting should I be using to have the camera correctly calibrate the brights and darks? I have yet to try the kit and zoom lenses under the same condition.
    Best of Both worlds:
    dSLR: Sony a100 dSLR w/ kit lens (18-70mm)
    Minolta Lens Collection: 28-80mm xi, 70-210mm
    Point and Shoot: Sony DSC-T11

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  2. #2
    Join Date
    Jul 2005
    Posts
    6,590
    The camera clearly has metered for the wall of the right building most of all.
    Try to tell the camera yourself what to meter for, for instance with spot metering and then meter with that spot on what you think should be exposed correctly (and metering on a mid tone while doing so).
    The buildings will become darker of course, when the green/light central part will get better exposed.
    Canon EOS 350D, Tamron SP AF 90mm F/2.8 macro, Sigma 18-50mm F2.8 DC EX, Canon EF 70-200mm f/4 L USM, Tokina AT-X124 Pro 12-24mm F4, Soligor 1.7x C/D4 DG Teleconvertor, Manfrotto 724B tripod, Canon Powershot S30

  3. #3
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,560

    Lightbulb F-stop range issue

    My question is: What was the subject of the composition ... the bark of the birch trees? With this much range in the f-stops, this decision could be kind of brutal, as a digital camera only has 3 f-stops of dynamic range to play with.

    If those trees are at f/22 or f/32 and the wall at f/5.6 ... you are going to have an unbalanced exposure. The walls really need to be around f/8 at the minimum, to show any definition, as you begin to close down your aperture to adjust for the trees. You could try "fill flash" to brighten up the nearby walls and help the f-range get a bit closer. It's just a thought. You're going to need some serious flash against that kind of sunlight.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  4. #4
    Join Date
    Dec 2006
    Location
    Toronto
    Posts
    155
    Thanks Guys. I will keep working with these tough exposure situations, and will try those suggestions.

    These shots are by no means artistic (i.e. what is the subject?). I just got this a100 machine and decided to take the hard road by shooting under high-contrast situations!

    "... a digital camera only has 3 f-stops of dynamic range" - what do you mean by that? Is this in reference to exposure compensation?
    Best of Both worlds:
    dSLR: Sony a100 dSLR w/ kit lens (18-70mm)
    Minolta Lens Collection: 28-80mm xi, 70-210mm
    Point and Shoot: Sony DSC-T11

    My photo portfolio

    My Flickr

  5. #5
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,560

    Red face The "learned" few

    Okay ... it is explained this way ... so be patient.

    You take a light meter (or your camera's built-in meter) and measure your subject. Let's say the meter says the bulk of your subject is at f/5.6 @ 1/125 sec @ ISO 400. Thats pretty bright, actually. You should have as good shot, overall.

    So, as you are aware ... the f-stop scale goes up and down in increments.

    Darker - requires wider aperture
    f/1 - Black (doesn't change in intensity)
    f/1.4 - Black (doesn't change in intensity) Black doesn't change
    f/2 - Black (doesn't change in intensity)Black doesn't change
    f/2.8 - Blackest black for this image
    f/4 - gray
    f/5.6 <- Exposure center (The lens' aperture is set to this reading)
    f/8 - bright
    f/11 - Whitest white for this image
    f/16 - White (doesn't change in intensity)
    f/32 - White (doesn't change in intensity)
    Bright - close down aperture

    Okay ... with only three f-stops for your sensor's dynamic light width, with your lens' aperture set to f/5.6, anything measuring f/2.8 or wider, on the light meter, will be effectively black to the sensor. Anything measuring f/11 or greater with be blown out or white. It is the same way for color film (3 f-stops range) ... so if you use the summertime high-noon sun as your source, you are usually dealing with nearly 7-f-stops of light to manage. Once again, stuff in the shadows quickly goes to black and anything hit directly by the sun ... blown out. Let the sun set a little, it's easier to manage the light.

    You think this is bad, just try using transparency or slide film. It has only 1 f-stop range. If your exposure isn't "dead nuts, right on", you get either a black or white image. I hate that stuff. You have to bracket your shots, just out of self-defense and to not waste time having to re-shoot.

    B&W film has the greatest dynamic light range of just about anything out there ... a full seven f-stops. Looking at the scale, you effectively would get this kind of range for your image.

    f/1 - Black (doesn't change in intensity)
    f/1.4 - Blackest black for this image
    f/2 - dark gray
    f/2.8 - getting gray
    f/4 - slightly gray
    f/5.6 <- Exposure center
    f/8 - brighter
    f/11 - brighter
    f/16 - brighter yet
    f/32 - Whitest white for this image

    Is this making any sense? Yes, we are talking about the digital sensor ... and not film. And yes, you can set the lens to whatever exposure aperture you want to, but the sensor can only vary its relative sensitivity 1 1/2 f-stops higher and 1 1/2 lower to display your overall image. If your image's light range is wider than that ... the difference in the highlight and shadow detail suffer.

    How we doing?
    Last edited by DonSchap; 05-11-2007 at 11:46 AM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  6. #6
    Join Date
    Dec 2006
    Location
    Toronto
    Posts
    155
    Hi Don, I think I understand it. I'm printing out what you explained and will read it several times.

    One thing to note is that the other zoom lenses (f/3.5 to start) do not over-expose. The 50mm f1.7 has completely washed out shots, at shots like 1/125 f5 or f/320 f/4 under even brighter conditions (mid-day full sun-light). From what you wrote, the sensor needs to have a smaller aperture.

    I've updated the firmware to 1.02 and have yet to test. If it is lens-specific, i'll simply have to apply -M-anual mode when this lens is used.
    Best of Both worlds:
    dSLR: Sony a100 dSLR w/ kit lens (18-70mm)
    Minolta Lens Collection: 28-80mm xi, 70-210mm
    Point and Shoot: Sony DSC-T11

    My photo portfolio

    My Flickr

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