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? for the pixel peepers

Discussion in 'General Technical Discussion' started by cwilt, Jun 28, 2007.

  1. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    A little background first....

    I have a shot that has escaped me for a couple of years now. There is a neon blue sign on the Qwest building in downtown Denver. I'm guessing its about 18 miles away as the crow flies. I have yet to be able to resolve that sign well enough to read the letters. At first I thought it was just the lack of focal length. I have tried out to 1000mm on different nights with no success. Atmospheric conditions was my next thought. Tried it in many different conditions and still no go.

    No photographic content in this exercise. Doing it just for the challenge. I'm just odd that way. :Wink:

    My current opinion is that a Bayer type sensor can not resolve the blue well enough. Has anyone done resolution tests based on color?
     
  2. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    It might be the wavelength of blue light is not corrected by the lens as well as the other colors. Or perhaps scattering.

    Regarding the sensor's color filter, there are the same number and spacing of red filters as there are blue ones. Yet red does not show those characteristics. Or does it?
     
  3. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    This is possible and something I have not looked at yet.

    I believe that a pure red will show the same effect. For example, a red rose does not resolve well. On a bayer sensor a pure red or blue will only have 1/4 of the total resolution. So my D2x becomes approximately a 3mp camera when confronted with these types of subjects.
     
  4. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Anyone else?

    Am I barking up the wrong tree?
     
  5. <WAG>

    I would guess that red and blue will be most prone to color interpolation errors with a Bayer sensor since it is more sensitive to green and has more information to use in the "nearest neighbor" calculations that are employed.

    Blue light scatters more in the atmosphere relative than red or green since blue has the shortest wavelength of the three, but that may be irrelevant to the problem you describe. My guess is that it's the sensor configuration.

    </WAG>
     
  6. I experienced similar effects with neon signs, mostly in night shots. I always blamed it on their high brightness relative to their surrounding. Given your theory, a green neon sign should be no problem, right?
    Unfortunately I currently don't remember where to find a green one, but I'll certainly remeber when I see one.
     
  7. ckdamascus

    ckdamascus

    928
    May 14, 2005
    New Jersey
    Did you try underexposing?
     
  8. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    I don't have a green one handy either, but if I run across one I will try it and see.
     
  9. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    I did and gained nothing.
     
  10. ckdamascus

    ckdamascus

    928
    May 14, 2005
    New Jersey
    Insanity!!! So at 1000mm does it fill the frame?
     
  11. Bob Coutant

    Bob Coutant Moderator Moderator

    May 17, 2005
    Pleasantville Ohio
    How does the sign appear when viewed through high power binoculars or a telescope?
     
  12. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Not even close. I am talking about pixel resolution of the finest degree. At least, I think so.

    Never tried it with binoc's and don't own a scope. Why did you ask that? Curious as to what you were thinking.
     
  13. Bob Coutant

    Bob Coutant Moderator Moderator

    May 17, 2005
    Pleasantville Ohio
    Charles, I thought that might tell you something about atmospheric dispersion. [Trying to separate camera effects from other possible interferences.]
     
  14. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    There isn't many nights out of the year that I will attempt this shot. So far I have had only 3 clear nights without wind to try it. Lots of haze or pollution, or the wind was blowing.
    :mad: 
     
  15. Charles can you post some image for me so that I get a better idea of how far away the sign is and how big it is, maybe with a 100% :smile: ?

    So that when I encounter a blue neon I know if the scene would be similar to yours?

    Btw. that reminds me that I quite often had the same problems also by my own eyes. Do you have a green LED somwhere on your computer or else, maybe even a bright one?
    Do you have difficulties in having a sharp picture of it (with your eyes! no camera!)? I never that any difficulties with that.

    Now do you have a device with a bright blue LED on it? Try the same. I always felt it to be very uncomfortable to look at them, especially if they're bright, and if they were reasonably bright, I always had difficulties to get a sharp impression by looking at them.
    I know some other people I had talked with about that who confirmed that they feel the same.

    I don't know if these effects are related to each other, but I thought it was at least worth mentioning.
     
  16. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    I was actually playing around trying to capture some fireworks that were going off downtown and I think that sign was in the scene. I was shooting with the S5 tho. I will process and post so you can get a better idea of what I am seeing.

    Green is no problem. The only blue-ish led I have is my led torch that I use for light painting. Don't want to look at that.:eek: 
     
  17. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Made a couple of test shots tonight.

    Sigma 50-500 + Sigma 1.4TC = 700mm
    Used 1 second exposure at f11
    If I tried to shoot longer than that the D2x would bloom.
    Tripod mounted, MLU, with wireless release
    ACR was used for both with default settings except the S5 was interpolated up to 12mp, 600x600 crop, converted to sRGB 8bit and saved as a jpeg level 12

    One is D2x, the other is Fuji S5
    Can you pick which one is which without looking at image data?

    [​IMG]

    [​IMG]
     
  18. I think it's just an overall resolution thing. The red beacons and other light sources aren't sharp either.

    I happened to take a picture of a blue neon sign in June. Hardly the same distance away, or under the same conditions as yours - but I don't think the blue did anything particularly odd. It could have been given a little less exposure though:

    (D200 w/Nikkor 18-70, 1/50@f4.5)
    p165002686-4.

    Cropped:
    View attachment 103186
     
  19. Charles, I had the same impression as Scott. To me the "white" and red look as unsharp as the blue sign so that I would guess that it's no matter of the blue channel alone.

    1st S5, 2nd D2X? (brave guess)
     
  20. Bob Coutant

    Bob Coutant Moderator Moderator

    May 17, 2005
    Pleasantville Ohio
    Charles, the DPR review of the S5 is finally out -- thought you might be interested in comparison of their results with yours.
     
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