Spring 2012

Spring 2012
by ani

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I need to photograph paintings, and also small details of paintings. Color accuracy is extremely important.

Previous experience (not recent, however) with digital photography showed color divergences between the original artwork and the photographed artwork that I found utterly stunning.

The images are going to be displayed in a format not less than 3 feet high, possibly more.

I'll be shooting in a museum setting.

Sigma's option seems to have drastic limitations (proprietary lenses and post-processing software, as well as the lack of live view), although I love the idea of a Foveon-sensor camera for this. I'm not sure whether a Bayer sensor does the trick or not.

What type of gear is essential to photograph paintings with accurate color?

EDIT: The camera/sensor aspect of the question is not satisfactorily answered by the previous thread referenced here.

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marked as duplicate by mattdm, Michael Clark, Philip Kendall, Dan Wolfgang, John Cavan Jan 23 at 14:28

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
Thanks to everyone already. Recognizing the relevance and primary importance of all the workflow and other topics raised ...is the choice of camera - and especially its sensor technology - a completely trivial part of the set-up? – Wombat Pete Jan 19 at 21:32
    
Questions for specific product recommendations are off topic here because they quickly go out of date and are often specific to just one person, so I think people are trying to tell you what kind of gear you need without choosing a specific make and model. And since most digital cameras from point-and-shoots to DSLRs use a CMOS sensor with a Bayer filter, they're all going to detect color in about the same way. How you light the subject and interpret the data from the sensor will have much greater impact than your choice between Nikon, Canon, Fuji, etc. – Caleb Jan 19 at 22:02
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Adding to the excellent answers below: "color accuracy" is a difficult topic, as color obviously depends on lighting. The exact same painting can look very different under different lighting conditions. So you may have something that is an accurate reproduction of the painting in a given setting, but that does not make it universally accurate. – jcaron Jan 19 at 23:19
    
jcaron, that's true, of course. Let's presume we've successfully created maximally event and dispersed full-spectrum lighting. – Wombat Pete Jan 19 at 23:37
    
Caleb, thanks. Part of the question was about whether the choice of those cameras or options with other sensors might be an important part of the process. – Wombat Pete Jan 19 at 23:38

The gear actually isn't as important in your situation as the workflow to preserve color accuracy. The main issues you'll need to consider are:

  1. Accurate white balancing when shooting. This typically involves shooting in RAW format (so you need a camera that shoots in RAW) with some type of color reference in the frame--something like a WhiBal or ColorChecker--and then using that to white balance off in post, typically using an eyedropper sampling tool to set a white or gray point. If absolute-spot-on color accuracy is not required, but only good-enough-to-eyeball matching (i.e., to avoid having heavy orange cast from tungsten/incandescent lighting, blue from flash, or green from flourescent), this might be enough without a lot of additional outlay.

  2. If it has to be spot-on, however, then you need accurate color calibration of your camera, your monitor, and your printer. This will probably require specialized hardware and/or software, and there is no getting around that. At each stage along the way, how the colors are represented internally can be out of calibration with the other two. So you need to make sure that each is accurately calibrated or profiled in a way that ensures you consistent and accurate color representation. To do this, you are most likely to need:

    • A color reference card
    • Software to turn shots of the color reference card into a camera profile you can use in your post processing package of choice.
    • Monitor calibration hardware--something that can sense the color coming from your monitor
    • Monitor calibration software that can take the hardware readings and adjust the settings on your monitor based on them.
    • Printer/paper combination ICC profiles (can come from the manufacturers of the printer, paper, or inks when you purchase from them or download from their websites).

Note how nothing on that lists indicates a specific camera or sensor type. Color accuracy has little to do with the sensor hardware these days, since all of them are pretty good, and variants such as Foveon or X-Trans sensors, while they do give you some advantages, must still go through this same workflow to ensure color accuracy.

For shooting paintings and closeups of paintings, however, you're most likely to be happier with a camera or camera/lens combination that can provide you the following things:

  • Full Manual mode, for exposure control over iso, aperture, and shutter speed.
  • RAW capability
  • macro capability [may require a separate lens with an interchangeable-lens camera]
  • Some way to use off-camera flash (typically a flash hotshoe)
  • A tripod mount hole
  • A cable release port

Shooting paintings typically involves controlling reflections and showing texture by controlling and/or diffusing the lighting, shooting details typically involves shooting close-up, and you may need to be able to shoot in lower light or from specific angles, so using a tripod and cable release can come in handy.

See also: http://news.smugmug.com/2014/05/14/the-art-of-copy-work-photographing-artwork-accurately-without-glare/

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A powerful flash in a museum might of course be frowned upon ... – Hagen von Eitzen Jan 19 at 22:19
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+1 for the colour chart. Without a reference (could also be a grey card, but colour chart would be better) there is effectively no way you can every be certain of the accuracy of your colour. – DetlevCM Jan 19 at 23:11
    
@HagenvonEitzen, I was thinking more along the lines of a speedlight rather than a studio strobe. But point taken. From a conservation standpoint, any lighting might be out of the question. – inkista Jan 19 at 23:54
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Only thing this answer lack is controlled, good light source if you can get it. Under some lamps I found it impossible to get the colors accurately, and the better color rendering of lamps used, the easier further steps. – Mołot Jan 20 at 14:59
    
@Mołot I figured the statements on flash and controlled/diffused light covered that. YMMV. – inkista Jan 20 at 17:05

I used to work as an assistant to a guy who shot accessions for the Corcoran Gallery in DC. He used a standard copy photography lighting technique with two Lowell D (now DP) hot lights reflected out of 60" silver umbrellas placed at 45° angles to the art on each side of the camera with their throw pattern overlapping a bit for greater evenness across the surface of the artwork which he verified using a Sekonic incident light meter to make sure the light was completely even across the entire surface area. In instances where it was important to emphasize any texture in the surface of the artwork he would adjust the placement of the incident light to a more acute angle to bring that out.

He used a polarizing filter on the sharpest and most accurate camera lens available at the time (55mm f/3.5 Auto-Micro Nikkor manual focus) to minimize glare. He would also include at the edge of the art a set of color swatches in order to be able to accurately reproduce the color of the artwork when printed. A sturdy tripod was necessary and he'd use the camera's self timer to enable the camera's reflex mirror to lock in the up position prior to the shutter opening thereby minimizing camera shake during what was anywhere from a ¼ to 2 second exposure time depending on the distance the lights were from the subject matter & his desired f/stop for sufficient depth of field.

You'll have to decide on what lens currently available gives you the best sharpness, least field curvature & distortion across the frame then match that up with the camera body that fits it and offers mirror lockup and minimal shake for the sake of image sharpness as well as the least amount of in-camera image processing for its RAW format.

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KarlC, thanks! I appreciate your experience, extremely useful. – Wombat Pete Jan 20 at 1:47
    
Mirror lock-up is a good point (though there is a lot of debate on whether you see the impact, especially outside of a tele lens). BUT: There is no need to use the self timer. A cable or infra-red remote works just as well - mirror lock up is an independent function - however if you do not have a remote the self timer is the second best option to reduce camera shake on the tripod. – DetlevCM Jan 20 at 18:33

Some general recomendations.

1) The resolution of the file.

You need at least 150 ppi for this. At 3 ft you need 3x12x150=5400px on the long side. So you need a 24Mpx file at least.

2) You want a sharp lens.

Try a Prime lens for this. The longer focal length the better becouse you reduce barrel distortion. Lets say an 85mm.

3) Good ilumination.

a) You need an uniform lighting, for example 2 or 4 lightsources at 45 degree angles. Probably difuse light.

This is not mandatory becouse you could have the case the painting has a lot of 3D texture, like rocks or sand, then you need to play with the light and shadow.

b) You should prefer a continous light source with a good spectrum. Avoid fluorescent lamps if possible. https://www.google.com.mx/search?q=continuous+light+spectrum+fluorescent+vs+led

4) Incident light meter. For a more precise aproach you should measure the light with an incident light meter. The light diference should be less that 1/2 - 1/3 stop on all the original paint.

There are some sekonic models that allows you to find the real tonal range of your camera. https://www.google.com.mx/search?q=sekonic+find+tonal+range+camera

5) Calibrate your workflow.

d) You need a color chart target like this one: http://xritephoto.com/colorchecker-passport-photo

e) Color calibration hardware like this one: http://www.xritephoto.com/custom_page.aspx?PageID=299

f) or a more pro solution like this package: http://xritephoto.com/ph_product_overview.aspx?ID=1913

So. Calibrate your camera. Calibrate your monitor. Calibrate your prints.

(It is usefull to prepare a custom white balance inside the camera, but as you are using the raw files it is not completly necessary)

6) Use a good monitor.

7) Shoot in raw.

Look for tutorials on how to manage a well calibrated workflow with the previous equipment. https://www.google.com.mx/search?q=xrite+color+checker+workflow+tutorial

In this case you need to use Adobe Lightroom becouse you can use the color profiles given by the Xrite calibration hardware and targets.

Use the ProPhoto color space. https://www.google.com.mx/search?q=adobe+prophoto+color+space

8) Use a tripod.

9) Use a good printer

This is another topic by itself, but you want photographic quality prints, probably latex based ones. You need a service bureau that allows you to make some tests, and if you come the next day they mantain the same configuration on the equipment.

Use this recomendations as starting point to find out more. Yes... you have homework to do.

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All the other answers are correct. However there is one aspect missing:

Don't expect more than what is technically possible

Art is the single most demanding type of photography because it asks for colour accuracy. More often than not it is impossible to create a colour-correct print of an artwork. The reason is simple:

The colours that Artists use are not available to a photographer.

For example Gold or Yellow-Marker colours. Artists will often use "anything" that gives them the correct impression of their art. They usually don't think about a reproduction.

Most people perceive Artwork very different than other types of photography. On a Landscape picture nobody will carefully check the colours if it renders the mood correctly. On Portraits most people are even glad if not all details of their face are reproduced colour-exact. This is very different with Art. Even laypeople will search for "that special shade of orange" in a painting.

Most technically minded people will suggest a technical solution. But this does not help here. The correct technical solution is to use a separate colour channel for each colour of the artwork. This is technical overkill. (But as a remark: two or three additional channels can already improve the result)

How to create a decent result

It is possible to create a decent result with a moderate overhead. The human eye is an amazing colourimeter. Don't let colourspaces dictate your perception.

Bring the expectation back to reality

  • Don't expect too much. Even the best camera has a hard limit to its colourspace. The piece of art in front of the camera ignores this happily. There will be shades of colours that will not be on the final picture. Explain this early on to your customers, this prevents false expectations from their side.

Aim for the best technical quality

  • Use RAW image format. There is already a problem with the size of the colourspace. Do not limit it further by using jpeg.
  • Use decent lighting. The light source needs to provide "all colours". The camera will not see colours that are "not lit".
  • Put a colour- and grayscale next to the artwork onto the photograph (along one of the edges). The painting may have special weird colours, but not any "normal" ones. The scales will provide these. This helps to calibrate the workflow.
  • Throughout the workflow use the best available image formats.
  • Expect significant time for post-processing the image files. Depending on the type of inks and paints used in the artwork you might need several combinations of filters and masks. This may be the only way to get a print that "looks similar" to the original.
  • Use the best printer available. 6-colour is better than 4-colour, and 8-colour is better than the other two. Make use of additional colour channels early in your workflow whenever possible.

Trust your eyes

  • Have all persons(!) that work somewhere in your workflow visit the artwork/museum. They need to see how the original looks like to be able to produce the same impression on print.
  • Check the visual impression of the prints. Trust your eyes. If you like the result, it's OK. Don't let an instrument judge your work when you know that the instrument is wrong.
  • Take the prints back to the museum. Check the visual impression there.
  • Be aware of possible colour vision defects. In this case work together with another person.
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Why would the colour space be limiting? - The camera does not have enough dynamic range? Get a better camera - or if that isn't enough, use an HDR type technique to maximize the amount of captured detail. Given that a painting tends to be very patient, you are free to use every possible technique to compensate for any drawbacks in the camera equipment. BUT: One thing would be impossible to compensate - a weird spectrum in the light sources. – DetlevCM Jan 20 at 18:36
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@DetlevCM Even the best cameras available can not reproduce the full spectrum of visible light. And even if the cameras could, the best printing processes available certainly can not. The colors present in the art that are not reproducible have to be represented by colors that can be reproduced. Dynamic range and HDR have nothing to do with reproducing out of gamut colors - They only allow a wider tonal value (brightness) to be represented in an image that is produced by a method with a lower maximum dynamic range. – Michael Clark Jan 20 at 20:40
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@DetlevCM, Adobe RGB maps only about 50% of the visible colours. Adobe Wide Gamut RGB only about 78%. This problem is technically not solvable today. But you can get a decent result non-technically. (with "technical" I refer to color spaces) Sometimes it is better to forget about colorspace, gamut and range. The human eye is your best tool here. The end result has to please your own eyes. – Bogdan Willi Jan 20 at 20:58
    
@MichaelClark Have you got a reference for that? It does not sound right to me - googling does not bring up anything useful. Wikipedia suggests a sensor covers more than the visible spectrum, BUT it isn't a reliable resource. Plus, there is always the image of a multiple camera setup ;) - en.wikipedia.org/wiki/Full-spectrum_photography , missionscience.nasa.gov/ems/09_visiblelight.html , extremetech.com/electronics/… (last link on modifying filters which limit the spectrum on a common camera) – DetlevCM Jan 20 at 21:54
    
@BogdanWilli There are wider colour spaces than Adobe RGB - for example ProPhoto RGB digital-photo-secrets.com/tip/2401/… Apparently some lab colour spaces are larger, but can't find a source other than a post on a forum right now... Whether you can show it on a single display or print is is another question - but you can definitely record a lot. Yes, "recorded light" will be in discrete values, but with small enough steps, these will be indistinguishable from continuous data. – DetlevCM Jan 20 at 21:58

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