Photographing Paintings - Modelling Lights Not Enough For Auto Focus?

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Andrew
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I've been photographing my paintings in a dark studio using two Lencarta Smartflash lights. I was wondering why the auto focus wasn't working? For the first time in a while I photographed outside today and it worked perfectly. Presumably the modelling lamps aren't throwing enough light upon the paintings for the autofocus? Have I missed something in the setup of my camera (Nikon D3200)? Otherwise what would I do?
 
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What focus mode, what focus point? What are you trying to focus on?

There should be enough light, but focussing on a 2d surface could be tricky if there’s no area of high contrast.
 
Well the pictures are static I assume so tripod mount and manual focus should work.
 
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I can't remember what focus I set the camera to, but I know I read the manual to attempt optimising focus for a painting. I generally move the focusing 'rectangle' to an area where there is a contrast. But usually end up manually focusing when the auto focus fails to click.

Manual focus is ok, but I always need to take several exposures to get one that is pin sharp. It's quite dark with just the modelling lights for manual focus.
 
When I had a D610 that would really struggle to lock focus in lower light, even with a fast lens. I would either manually focus (does the D3200 offer focus confirmation?) or suggest adding a desk lamp to provide extra light to focus.
 
suggest adding a desk lamp to provide extra light to focus.

How would this affect the resulting photographs? Would the flash lights negate any additional lighting?
 
I can't remember what focus I set the camera to, but I know I read the manual to attempt optimising focus for a painting. I generally move the focusing 'rectangle' to an area where there is a contrast. But usually end up manually focusing when the auto focus fails to click.

Manual focus is ok, but I always need to take several exposures to get one that is pin sharp. It's quite dark with just the modelling lights for manual focus.
What aperture are you using?
Are you using a tripod and remote release?

There are a number of things that can affect sharpness such as, camera shake, choice of aperture, the lens itself..................................
 
I think the camera would have the best chance in that scenario using live view's contrast detect auto focus (CDAF).
Otherwise the answer is pretty simple... turn on the room lights, focus, disable AF, turn off lights; or some version of that (attach a speedlight that can throw a focus grid, use a flashlight, etc).
 
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I have Godox X Pro flash remote control transmitters for my cameras. In the neck of these transmitters is a laser head behind a red plastic window in the transmitter case that I can turn on when trying to take photos in low light, and will project a cross hatch laser beam of light on the subject during the auto focusing step of my cameras. It's only lit during the auto focusing sequence and turns off automatically when the auto focus is complete. When I press the shutter trigger button the rest of the way, the laser is off and the shot is in perfect focus.

Back in my very early days of digital photography this feature wasn't available. To get the camera to focus automatically in low light conditions it was quite a challenge. I came up with an idea to use a laser gunsight and modified one so I could attach it to a cold shoe on the camera. I could turn this laser on and the red dot on my subject/model would let the camera focus perfectly. I learned quickly to explain and demonstrate the laser to those involved, because the first time that I turned it on, everyone hit the floor, thinking that I was pointing a gun at them. After the explanation, there was no problem with using it. Since it was always on during the shot there was a red dot in the photos taken, but it was easy to remove this in Photoshop during post. Fast forward 23 years and it's now an automatic feature in flash control transmitters and called "Focus Assist" and it's only on briefly during the auto focus function of the camera, so the red dot removal via Photoshop is no longer needed. The cross hatch pattern doesn't scare anyone like the single red dot did either, and it's on so briefly that many are not even sure that they saw it. I can manually turn this laser on or off via a switch on the side of the flash transmitter, but usually just leave the switch on.

While cleaning and reorganizing my camera bags last year, I rediscovered this gunsight laser unit in the bottom of one of the pockets of one of my camera bags. I was amazed that it still worked, I had forgotten about it years ago. It went on the shelf with my no longer used cameras because I doubt that I'll ever need to use it again,

Charley
 
A good friend of mine who did a lot of this sort of thing for auction houses in the '70s and '80s, taught me a great wheeze. He carried two strips of satin milliner's tape with little hooks at one end and small weights at the other. Whenever he needed to photograph flat work in bad light, he'd drape the tapes over the surface and light them with an ordinary torch. The reflective tape provided an excellent focussing point and was easily taken down before pressing the shutter release.
 
How would this affect the resulting photographs? Would the flash lights negate any additional lighting?
You can always use another light for focussing then turn it off to shoot. On my Fuji cameras I use manual focus, but attain focus with the AFL button, for such subjects. Mirrorless cameras are inherently accurate as they focus with the sensor.
 
If you haven't placed your lights correctly it's easy to get reflections and hot spots when taking photos of pictures too. Place your lights 40-50 degrees left and right of the camera 3-5 ft from the picture and you should be fine, but you may need to adjust them further, depending on how rough the surface texture of paintings. Adding a third light high above the camera can sometimes help with texture problems too. All should be soft lights, with GOBOs like soft boxes, shoot through umbrellas, LED Panels, etc.

Charley
 
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