Quite some time ago I was involved in photographing some oil paintings for a collection, about 90 of them.
We found the best technique was to have the lights at 5º from the painting plane, which appears to be almost parallel but isn’t. By checking with a light meter we positioned the lights so they were exactly equal in output at the dead centre of the paintings.
Then we moved one light back so that it was 1/10 of a stop weaker at dead centre. This gave a very slight modelling to the 3D of the paintings.
We weren’t too sure whether the owner would like what we suggested, so a test was duly done and processed (EPN). One quite happy customer, so we went ahead.
Food for thought.
One other aspect was that we used a 5x7 camera with a 150 lens and a 4x5 back. When confronted with a wider or taller painting, we converted the back to 5x7, kept the 150 on the front and effectively had a wide angle lens, still with appropriate coverage. This made life extremely easy and aided efficiency enormously.
That sounds good; the low light angle is what I've inadvertently ended up doing on my last couple of outings. Unfortunately, I sometimes have trouble setting up in a space large enough to allow much adjustment. Each pass I usually find some new useful detail -- a semi-annual learning experience!
Florescent light contains UV, so you should be careful not to expose the painting for a long period to such light otherwise it can harm the painting.
Thanks for posting this concern. I have also been researching about proper lighting effects. This is a big thing to learn in photography.
UV and the heat are not welcome. I have 1950s German magazines and they were teaching how to photograph an icona. They were using Linhof and and lights like ARRI Cinema lights . They were all placed at 3 meters and just front. Results were the ugliest reproductions I have ever seen.
Let me share with you a trade secret , when I want to learn an museum critical information , I contact with them.
British Museum always responds in few days. Or you can try Louvre Museum. they still sell film reproductions and they know the best.
I think best technology for reproduction is comes from Italy. They use gigapixel cameras and technology like spectrometer . I had been posted Mona Lisa current and digitally cleaned and yellow green cast removed. They are from Florence and if you search it well , you can reach it.
This site is interesting.
What will you do with films ? Above site teaches how to print it with inkjets.
To my knowledge and with the use of a descent digital camera ( which can adjust the white balance) the use of florescent light causes not really a problem. Taken that you place the lamps in the right angle ( about 45° ) it should come out pretty descent.
The trick is to use a software program ( I use capture one ) where you can adjust the white balance with the click of a mouse. I use my camera tethered, so control is complete over the computer. With the use of a grayscale card the colors are corrected easily.
Although I would recommend the use of flash strobes.
Hope this helps.
Many have given good advice but I did not notice the suggestion of taking some control shots including a color checker card and gray scale in the picture. The color balance and values of the final output could be adjusted to match as closely as possible. If the capture is on film remember that different films have different color characteristics. Information from a museum or a restorer was a good suggestion.
For color critical work, I always test film with a Macbeth color checker to see if the batch of film needs correcting. I also include a step wedge and Kodak color chart in every shot. This helps the printer with color separations of the transparency. Again, I preferred Kodak EPN for art documentation. Fuji chrome films are too distorted for art documentation work. I love Fuji film for personal work though. I don't know if a high CRI light will benefit any shot at all. I thought high CRI numbers only benefited viewing for the human eye, not for film. Correct me if I'm wrong. And yes, heat and UV are enemies of art work.