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12-03-2018, 08:55 PM   #1
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Shooting white background artwork

I have created silverpoint artwork.. Its on a dead white ground (made with marble dust).. its VERY white.. White is zero density, and the artwork greyscales up in darkness to about a max of 70%. So the range is pretty narrow but it starts at zero.

I've tried using the manual white balance setup. But it does not set a "white point" the spot in the image that represents the edge of blown out density. I used to operate drum scanners back in the 80's all up through the 90's. On a "real" scanner. You can set the point in the image that is the white point, and its balance, actually dial in the values you want that spot to be calibrated to. You then set the shadow point, and some selective color areas to map to.

All the shots I've done, with various Fstops from 5 to 11 all capture that white ground as a 1/4 tone. White balance, simple allows me to set the "color" of the white. But it does not allow me to set the drop out density area. I can drop the background by over-exposing the image, but then I lose all subtle starting density in the image.

I have good studio lighting, that is giving me good even illumination. (studio lights with diffusers).

Anyone have a method of getting there?

Thanks in advance.

12-03-2018, 09:07 PM   #2
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HDR to the rescue?
12-03-2018, 09:58 PM   #3
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QuoteOriginally posted by paulpixeld Quote
I've tried using the manual white balance setup. But it does not set a "white point" the spot in the image that represents the edge of blown out density.
You are correct, white balance does not set the white point. Instead it matches the image processor's spectral interpretation to the color temperature of the light illuminating your subject. Set your manual white balance to the color temperature of your studio lighting. Alternatively one may also set the white balance based on an 18% gray card exposure. The user manual may be helpful in that regard.

As for capturing the full detail of the work, it is probably useful to think in terms of intensity/brightness rather than density,* with a limit of 14 stops of range between black clipping at the low end and white clipping at the high end. Since the numeric tonal values are strongly biased towards the high end of the scale, the approach is to provide adequate exposure to record tonality at the low end (shadows) while taking steps to not throw away most of the highlight tones.

As noted above, the most common approach with an extreme high contrast subject is to merge a series of bracketed exposures to capture the full detail and tonality of both highlights and shadow while maintaining a graceful rendering of midtones. The approach is loosely termed HDR for high dynamic range and can effectively mimic several additional stops of capture range.

Your K-1 is able to do in-camera HDR with either immediate rendering to JPEG or capture to a special PEF/DNG RAW file for out-of-camera processing using the PDCU software that came with the camera. A third option is to capture a series of bracketed exposures with highest EV intended to capture the shadows and the lowest to capture the highlights. The bracketed exposures are merged in post-processing software to produce the final image. Using the camera's HDR abilities is the easiest option while merging a bracketed series with other tools provides the most control.

I would play with both the HDR feature and regular exposures and see what works best. It may be that HDR is not required and to be honest, I strongly suspect that to be the case. To aid in getting proper base exposure, you might want to consider using an 18% gray card for metering to the incident light using M mode as opposed to letting the matrix metering makes its best guess in an automated exposure mode based on reflected light. This should allow the high values to fall naturally into their normal range of brightness with full structural detail. I would turn off both highlight and shadow correction for this exercise and bracket both sides of the metered exposure to find the points where highlight and shadow detail are held.

Edit: I should have looked up "silverpoint" before offering detailed advice. Silverpoint drawings offer a very limited range of intermediate tones and should be easily accessible to a K-1 without resorting to advanced technique. A reflected light reading using an 18% gray card or incident light reading with a hand-held meter should support the full range of values in the artwork. Exposure compensation, if needed at all, should very mild, probably less than 1.5 stops either direction. The histogram should peak far right with the rightmost tail on the verge of clipping.

Silverpoint : noun
The art of drawing with a silver-pointed instrument on paper prepared with a coating of powdered bone or zinc white, creating a fine durable line composed of metal fragments.

Steve

* Density is descriptive when working with silver-based photographic negatives or when printing, but does not translate well when working with the positive (additive) image formed with direct digital capture.

Last edited by stevebrot; 12-04-2018 at 05:50 PM. Reason: clarity and completeness
12-03-2018, 11:14 PM   #4
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If the art work is flat (2-D) and does not have mirrored areas, the (f/ stops ) range should be from 100% (white) to the blackest black (deep velvet) which is around 1%, or a range of about 7 stops (and more likely 5 to 6 stops)--any dslr should be able to handle that--even slide film could just about do it! So why would you have a need for HDR, and the like?

---------- Post added 12-03-18 at 11:27 PM ----------

I have no experience with silverpoint, but with acrylic and oil paintings (not a smooth surface) polarizing filters on the lights and the lens (that being turned to effect) allow much improved contrast/saturation. It may be worth a try.

---------- Post added 12-03-18 at 11:41 PM ----------

Interesting: doing a quick search mention is made that it is difficult to photograph (due to reflections from the metal), and it is done at very low light levels (they don't say but likely they mean diffuse light), and the white background will be gray, and thus photo's do not give a realistic representation. Presumably that is what you are finding.

12-04-2018, 12:48 AM   #5
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QuoteOriginally posted by paulpixeld Quote
Anyone have a method of getting there?
  1. Shoot in Raw. Shoot a series of images in M mode (say 10), each half a stop (or go for thirds if you care a lot) apart.
  2. Check the raw histogram in rawdigger or rawtherapee and choose the one where the histogram for all channels fits in best.
  3. Develop to your taste.
Takes no time and is easy enough.
12-04-2018, 03:01 AM   #6
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The easiest first step to try would be to meter off a grey card or use an incident meter.
12-04-2018, 08:49 AM   #7
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QuoteOriginally posted by paulpixeld Quote
I have created silverpoint artwork.. Its on a dead white ground (made with marble dust).. its VERY white.. White is zero density, and the artwork greyscales up in darkness to about a max of 70%. So the range is pretty narrow but it starts at zero.

I've tried using the manual white balance setup. But it does not set a "white point" the spot in the image that represents the edge of blown out density. I used to operate drum scanners back in the 80's all up through the 90's. On a "real" scanner. You can set the point in the image that is the white point, and its balance, actually dial in the values you want that spot to be calibrated to. You then set the shadow point, and some selective color areas to map to.

All the shots I've done, with various Fstops from 5 to 11 all capture that white ground as a 1/4 tone. White balance, simple allows me to set the "color" of the white. But it does not allow me to set the drop out density area. I can drop the background by over-exposing the image, but then I lose all subtle starting density in the image.

I have good studio lighting, that is giving me good even illumination. (studio lights with diffusers).

Anyone have a method of getting there?

Thanks in advance.
I'm not sure what some of your comment means. Like, zero density. And then you mention drum scanners. Then back to your actual photo problem without much info. You shot at various f stops and your image is under exposed? is that the issue?
12-04-2018, 03:58 PM   #8
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If I understood correctly, and I can imagine a light-ish silverpoint drawing on a white background, it's like shooting snow.
Set Exposure compensation +2.00 Ev or thereabouts and you should get correct exposures.

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