copying painting
Old 05-08-2019   #1
twopointeight
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copying painting

I have to copy a 4X5 foot oil painting. The files have to be clean enough to make 16X20 prints. I have an XT2 with a Zeiss 50mm macro lens. At 200 iso and strobe heads at 45 degrees, will this give me what I need? I'm all Fuji, I would have to rent a larger sensor camera, but would rather work with what I'm familiar with.
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Old 05-08-2019   #2
Greyscale
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Perhaps stitch several smaller images together?
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Old 05-08-2019   #3
Doug
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Make sure to use a polarizing filter to remove reflections from the paint surface.
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Old 05-09-2019   #4
Chriscrawfordphoto
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You'll be fine. I do a lot of photography of paintings for artists, and I use my Olympus Pen-F and OM-D E-M1 mark II cameras. They make large giclee prints from my files, and they look great.

Paintings actually don't have a lot of fine detail, so a 20 or 24 mp image can be printed much larger than a same-size image of something in the natural world.

Your biggest challenges are going to be with lighting. It MUST be perfectly even over the whole piece. Use an incident meter with a flat diffuser (or lower the dome if you have a modern Sekonic meter with the moveable incident dome). Take a reading at the center and at all four corners of the painting. They must be identical, within 1/10 stop or you'll see the unevenness in the lighting in the photo.

The other lighting issue is going to be glare, which can be very hard to avoid if the painting has a shiny or highly textured surface. The lighting I have actually found that worked best for such paintings is actually very cloudy overcast daylight. I take the painting outdoors and put it on an easel. The light is usually very even and without glare!

Here's a couple of paintings I have photographed lately:

http://johnhrehov.com/product.php?product=14

http://johnhrehov.com/product.php?product=17

http://johnhrehov.com/product.php?product=9


I built this artist's website, too. I did not photograph most of the work on it; most of it was photographed years ago by others.
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Old 05-09-2019   #5
willie_901
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Photographing oil paintings with the highest standard of fidelity is time consuming.

I believe your camera and lens are sufficient for the task.

With a decent tripod and some patience it is possible to carefully center the camera.

The tricky part is the lighting. To control the lighting all the light should come from off-camera sources.
  • You must avoid lighting with mixed color temperatures.
  • You need to minimize glare and reflections. As Doug mentioned a polarizing filter is useful. A circular polarized filter on the lens is better than nothing. But the reflections and glare comes from a wide range of angles since an oil paint surface is three-dimensional.
  • The 3D nature of the surface also compromises using 45 degree lighting angles.
  • The optimum method uses cross-polarization with three linear polarizing filters. One goes on the lens. The other two go on the off-camera flashes or strobes. The lens and flash filters are set to be 90 degrees off axis. LP filter film is inexpensive so you can make you own flash filters.
  • Add a small of reflected light. When the polarization is set to completely eliminate glare, all brush-stroke detail is lost. This means rotating the lens filter by very small amounts can add just enough reflection to define the brush strokes without obliterating large regions of color detail. You make several exposures with slightly different lens filter orientations.
  • With strobes you need to avoid hot spots. This means you might to use wider apertures.[1]
  • If you use continuous lighting, constructing the polarizing filters is less convenient to avoid melting the filter film.
  • Use a grey card to calibrate the color temperature in post-production.
  • Use raw files and auto-bracket three aperture exposures by 1/3 stop.
  • The X-T2 can be tethered to a computer so you can optimize images in real-time.
  • For the final image rendering make sure your display is properly calibrated.

Sometimes the reproduction fidelity is not a high priority. This makes the job easier and less expensive.

An alternate method is to natural lighting. This requires patience. Outdoors you have to wait for a very cloudy day with calm winds. The light must be constant so the cloud cover needs to be thick. Now diffuse light comes from all directions and surface reflections are not an issue. You may need to flag the lens to minimize veiling flare. Some people with have access to large rooms with large windows. They use large reflectors to create even lighting with one color temperature. They use window scrims to diffuse the light to eliminate surface reflections.

1. If the strobes must be moved away from the painting the result will be a wider aperture which could reduce the lens' MTF50. I would start with base ISO (200 for the X-T2). In this case just increase ISO. Increasing ISO reduces the analog dynamic range. But in this case the DR will be well within the sensor's range with even a two-stop ISO increase. Shadow region detail decreases when ISO increases. However for art reproduction one does not selectively push shadow regions. With the X-T2 (and other pseudo-ISO invariant cameras) increasing ISO to maximize lens performance should not significantly degrade perceived image quality.
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Old 05-09-2019   #6
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Thank you for those detailed answers. Yes, this will be slow going to get it right. I'll shoot overcast light, with and without strobes on a covered deck. This is an important heirloom painting and budget is open to whatever it takes, so I can spend time, even a second day if need be?
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Old 05-09-2019   #7
KenR
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4x5 with 2 lights at 45 degrees from the painting. Place the camera off axis and use rear shift to center everything on the ground glass. Sorry, but this is how I was taught to do it.
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Old 05-09-2019   #8
rjschell
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Sometimes you need to polarize the lights as well as the lens.
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Old 05-09-2019   #9
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Some of the portrait papers used by photographers long ago made it difficult to impossible to copy due to the surface of the print reflecting in different directions. One solution was to move a light source all around the print during an intentional long exposure. I experimented with it a few times just out of curiosity after i had it demonstrated in a class. It worked, but i think Chris has a better solution with overcast sky-lighting.

Chris, is it necessary to wait for flat cloud surfaces or just a thick enough cover to keep the light even?
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Old 05-09-2019   #10
Dwig
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Chris' and Willie's suggestions are very good. I can only add that with heavily textured oil paintings you want to use the longest FL lens practical. A 50mm lens on APS-c is good, but a ~100mm lens would be better if you can deal with the longer shooting distance that results.

The purpose of the long lens is so that the angle from the lens to one side/corner is not too different to the angle to the opposite side/corner. The results in the rendering of the texture being more uniform.
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Old 05-10-2019   #11
willie_901
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Quote:
Originally Posted by twopointeight View Post
... I'll shoot overcast light, with and without strobes on a covered deck. ...

A covered deck could be tricky (or not, depending on how natural light reaches the canvas and if any strobe light reflects off the deck ceiling). The canvas should experience spatially homogeneous amount of light so the exposure and color temperature is constant over the entire canvas. Careful placement of natural light reflectors and, or strobe flags should be able achieve this. You can check for consistent exposure (and color temperature) by taking multiple photos with a small gray card held at different locations or with one large gray (or white) card that covers the canvas.

Strobes will be better than flashes as they can deliver more light and overwhelm uneven amounts of outdoor light. At the same time you need to avoid hot spots (uneven light) possible with high-power strobes.

I forgot to mention – using the X-T2's rear, articulated LCD as a viewfinder enables you to use the camera as you would use a twin-lens reflex camera. I found this to be very convenient for tripod work. The framing is accurate. There could be a very small crop factor depending on how much barrel/pin-cushion correction is used during post-production rendering.
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