High Dynamic Range Imaging – Toward Better Documentation of paintings

Photographing works of art, paintings, as I work mostly with them, is always raising questions and discussions about the “exact” rendition of colors. Is there a way to get the actual colors of a painting in a scientific way?  No, there is not. We have to accept it. We can’t just using a photo camera. I definitely believe that any attempt to achieve “perfect” color rendition image with a photographic camera doesn’t bring to anywhere.

For scientific and therefore repeatable color documentation you need specific instruments: spectrophotometers or a hyper-spectral imaging system.  The first category gives accurate color measurements –and it’s easy to use – but it’s limited to spot size sampling.  The second category allows you to get an image of all your art work where the spectrum of each pixel is measured but the systems are costly and complex to run.

As in the spirit of this blog, we are looking for answers in a contained budget – with an eye to medium-small museums or in general professionals working in the field who need a  “color- reliable” picture of a painting done with their photo camera.

There are some tweaks that should always be implemented and which constitutes the base of any good photographic practice – such as white balancing and the selection of the best color space in the camera.

This blog is about increasing dynamic range in your pictures using High Dynamic Range Imaging – shortly HDR – specifically for paintings documentation.  I’m sure it did happened to you to try to figure out how to exposure that painting with bright whites and pitch dark blacks, right?

Any commercial photo camera has a limited contrast range which results in the loss of detail in bright or dark areas. You have always to expose compromising between details lost in the brightest and darkest areas of your painting. HDR allows you to capture scenes with your camera that are just impossible to record with just one shot. With HDR you can take photos of scenes which have tremendous bright areas and deep shadowy areas and process them to produce an image with good exposure through both highlights and shadows.

There are many resources on the internet to learn HDR and at least 3 pieces of software. I used Photoshop CS6.

I used as a test a Sicilian devotional oil on canvas from a private collector. This painting doesn’t have actually that great dynamic range but some features are useful to show this method such as the bright left slice of moon upon which the Virgin stands and her dark blue dress.  I took three pictures at one stop bracketing, one underexposed, one at just right exposure (no blown out or totally black pixels) and one overexposed.

Three shots are necessary to compose a HDR image: underexposed, normal exposure and overexposed.

We need to make a HDR because we cannot get all the details with just one shot.

Indeed, in the underexposed picture the bright left slice of the moon is rich in details, especially compared with the one overexposed.

The details of this bright feature are lost in the overexposed shot.

On the other hand, in the dark blue dress, details are seen just in the overexposed picture.

On the dark blue dress details are registered just in the overexposed shot.

HDR allows to keep all those details in both dark and bright area.

HDR imaging brings together details otherwise lost in the under and over exposed photos.

 

HDR keeps details in the brightest areas.

 

HDR keeps details otherwise lost in the darkest areas

HDR seems an interesting tool to preserve in a photo all those details in dark and bright areas that our eye can see (the dynamic range of our eyes is much better than that of a digital camera) but that a single shot cannot record.