Underexposure in photographing drawings & artwork!!

Photographing Artwork

using Canon EOS 400, Photoshop & iMacI can’t photograph drawings using my Canon EOS 400, photoshop & Imac. The jpegs are always chronically underexposed.

I suspect that it’s the camera is underexposing. But I’m happy with the exposures when taking snaps of non-artwork out in the real world. Which leads me to suspect that the cameras algorithms are reading the actual painting as if it were the real world (not an illusion) and adapting the exposures accordingly. Result : every one of about two thousand jpegs I’ve taken are badly exposed. Even when I custom set the white balance in the camera.

Here are two jpgs, optimised for web, of a drawing made on A4 paper, of a ‘high white’ stationery kind of paper with artificial whiteners in the paper so it’s a ‘high’ white & not a cream. The light is bright morning sunlight. The camera setting is WB of 5200 K, neutral colour space. Here is the result just optimised at 500 pixels image-size & sharpened for the web.

And here is the same image after I’ve adjust the levels & corrected the blue colour cast via colour balance.

Is my iMac screen badly calibrated? It’s a 2001 generation.. the last of the cathode screens. I suspect it’s burnt out.

Here’s the settings for the iMac screen calibration…not the same as most PCs!

Here’s the colour settings for photoshop. Set to the’ web graphics defaults’ in sRGB IEC61966-2,1. Is this photoshop colour setting badly calibrated? Should i set photoshop to my screen , or to the average PC screen out on the web or should I find out the colour space of the canon camera & set it to that?

How does one get an web image calibrated for PC screens given the white point & grey gammas are much higher in an Imac? How do I calibrate my screen to the canon EOS 400?

Any help would be greatly appreciated!

6 Comments on “Underexposure in photographing drawings & artwork!!

  1.  by  My Camera World

    Most cameras when using automatic exposure settings want to make the average pixels values to a mid grey tone. (only basically true as it does a lot more).

    If you photograph a black cat it will be mid grey. If you photograph pure white snow with no shadows it will be mid-grey.

    A drawing on paper is mostly white and therefore as in the snow it will tend to turn it grey.

    The Cannon 400D should have settings to compensate for exposure and in the case you should try in the range from –1.0 to –1.7.

    Use the histogram to ensure that the data (pixels are at the right edge of histogram.

    The paper you are using will create a blue cast. The colour settings also are reasonable.

    I am not familiar with that ICC profile but I do notice that your white settings is set very high 9242K which makes the screen appear brighter but also tends to make blue stronger in tones.

    In the link below I made some adjustments. See if you like them

    http://www.pbase.com/nielsp/image/115562140.jpg

    Open jpeg in Photoshop Adobe Camera Raw (ADR) set exposure to automatic. ACR wanted to set the temperature +13 warmer. If the was a RAW file then I could determine the correct K temperature.

    In Photoshop added levels layer. Pressed alt key and moved right slider left to see where the brightest white points where he first patch besides sharpening artifacts showed up just left of her hips. I did the same with the black slider and alt to set where darkest blacks where and increase until I stared to see solid lines.

    Niels Henriksen

  2.  by  Adam Cope

    Dear Niels

    Many, many thanks for taking the time to respond to this thorny question of correct exposure.

    I couldn’t understand why the canon was underexposing on white paper/grey graphite drawings but seemed OK in snaps of the real world… so it is the algorithms.

    Basically it’s how the levels are written?

    The grey point is shifted up to the white point, in the hope that the midtones run smoothly & without strong contrast. Which explains why when I had a scanner it would read the white well but ‘crunch’ dwon the greys to black in a tendnacy to read high contrast white/black points with no grey points.

    Will try over exposing by one whole f-stop though the risk is that the black point become grey.

    Many thanks for balancing the guide; it’s more or less perfect for one source lighting (two sources would have got rid of the buckles in the paper). You obiviously know what you’re doing.

    The high 9242K is the native white point according to the Imac calibration software…. I’ll bear in mind that it’s bleaching & blueing the images. Thanks.

    Ideally I’d like correct exposures straight off with the minimum of photoshop correction. It’s a waste of time, works OK for web graphics but is garaunteed to go wrong for print ready images.

    In blogging drawings, the photograhing & blogging can take longer than the actual drawing, which does make me wonder if it’s worth it.

    Here’s a tip of graphite drawings, when the grey point has been shifted/bleached when the white point has been corrected. Rather than moving the grey point, I find that select colour > levels corrects the greys better than shifting the grey point in levels.

  3.  by  My Camera World

    I just realized that I used the minus sign when I should have used the plus to show that you increase the exposure, which you understood correctly, to make the grey-white whiter.

    Also to clarify another point in my comment. The reason I reduced the highlight triangle to the left in Levels setting was to find a good area for me to use the highlight eye-dropper to auto-select for whites. I hope this makes sense.

    Niels

  4.  by  Adam Cope

    I wonder if I shoot in Black & White if the exposures will not read white as grey?

    Impossible to take jpegs of watercolours as well.

    I prefer to manually adjust the levels than use the eye dropper. In generalmove the white then shift the grey back to where it was more or less. Then select colour range & darken greys.

  5.  by  My Camera World

    When shooting digital B&W then the camera will treat large areas of white as the same with colour.

    If your camera has a spot meter for exposure then try selecting the brightness white area.

    Did you look at the corrections I made to the drawing in the link above?

    Here is link again

    http://www.pbase.com/nielsp/image/115562140

    What the eyedropper does is correct for warm (yellow) or cool (blue tones) in selected areas. This makes it easier to compensate for the blue tones you had in the image.

    Please feel free to contact me anytime if you wish any assistance with camera or Photoshop adjustments.

    Niels

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