[loji]

So I have an opportunity to upgrade to a 645Z to do fine-art archival pictures for my work. These will be of oil-paintings, up to 90"x80" in size. (most will be smaller, human size)

I'll use an Xrite color checker, and I was thinking of what lens system would be best . . .

The options seem to be A35mm, DFA55 SMD, FA75, FA120 macro.

some of the paintings will be smaller (24"x36"ish) and I'll be taking them in a smaller space where I can only be about 6-10' away.... my gut says the 120 Macro will be too long to accomplish this. the default 75mm might fit that ... I imagine the 55 would be fine.

What do you think are the best options for me to start with for this project? Are there other lenses on an adapter I should be looking in stead? Significantly sharper, better color rendition? (color accuracy will be very important ... so I'm a little wary of A-series lenses, FA (at least in 35mm terms) have treated me better in this regard. there's a slightly dated 'look' to the A rendering.

[photoptimist]

Honestly, the K-1 with pixel-shift is the much better solution for archival fine art. The 645Z only samples the red and blue channels with 12.5 million pixels each and the green channel with 25 million pixels. The result then needs Bayer filter demosaicing which can introduce artifacts for highly detailed scenes (e.g., moire with the thread grid of a canvas). In contrast, a K-1 with pixel shift samples all three channels with 36 million pixels (3X the data of the 645Z in red and blue) with no demosaicing artifacts.

The K-1 will deliver better resolution, better color accuracy, and fewer artifacts. (Plus, it's cheaper so you can afford more lenses and sophisticated lighting.)

EDIT FOR ASPECT RATIO: As for the lens, a 80" tall painting shot from 10' (120") away on a 24 mm tall sensor needs a 24*120/80 = 2" = 36 mm lens or wider. If the working space from painting surface to the lens is only 6 feet, then you'll need something wider than 24*72/90 = 19.2 mm or wider. (You might need a bigger room!)

Lighting a painting can be tricky, especially if you must use a wider angle lens. You might need to use cross-polarization -- polarizing filters on the light sources and lens -- to eliminate reflections.

[ffking]

Lighting a painting can be tricky, especially if you must use a wider angle lens. You might need to use cross-polarization -- polarizing filters on the light sources and lens -- to eliminate reflections.

I'd second that - and add that even lighting is difficult to achieve - unless you have an enormous soft box, if you actualy test your lighting using a light meter at varios places across the painting, you'll see far more fall-off towards the edges than the eye notices - not so bad in digital days as with film, but you want to get it as good as possible in camera.

General question, since I've not done this in digital days - is picture stitching software good enough to use on large paintings?

[Vasyl]

Just some math about distances you will have to take shots from for 80x90 paintings
For 35 mm lens the min distance is 2.12 meters
55 mm - 3 meters
75mm - 4m
120mm - 6.3 m

To minimize distortions you have to use 75mm lens.
Good luck!

---------- Post added 25-10-19 at 08:29 ----------

wide lens will give distortions...shift adapter and 75mm lens may be the best option in this case...ah, I keep forgetting that K-1 has such option, so I tend to agree with you, that K-1 and pixel shift and sensor shift looks as the best option

---------- Post added 25-10-19 at 08:33 ----------

General question, since I've not done this in digital days - is picture stitching software good enough to use on large paintings?

shift adapter does not give distortion and may be the best option...stitching in PS is not the best solution. You will just have well aligned distortions, because you will be rotating your camera on a tripod by taking pictures from one point.

---

Last edited by Vasyl; 10-25-2019 at 08:57 AM.

[torashi]

You don't need to rotate the camera. But you'll need a rig where you can move the camera (and thus its sensor) parallel to the artwork so you can stitch in post.

I'd say invest the 645 Z money into K-1 + DFA100 + the rig. You'll be able to reproduce any artwork even at 1:1.

Lighting is a whole other issue apart from that.

I wouldn't worry too much about getting it all in on one frame. I'd be more focused on low distortion for stitching. And that it's a modern lens that what little's left can be corrected with software.

[swanlefitte]

You can use the triangle calculator to get angle of view.
For 80" at 6' you need aov of 64.02 degrees and at 10' aov is 36.86 degrees.

The opposite view of Vasyl.

That means a 35mm almost at 6' and a 70mm at 10' assuming I used the right sensor dimensions for 645z,(.79x crop)

[BarryE]

A least it's oils and not glass mounted watercolours and acrylics.

Of course there are oils and oils. An impasto technique will be harder to light than an oil painting that is more washed. Side lighting an impasto oil will not work. A large softbox as a key light above the camera illuminating the canvases in the same angle as the camera will help, but then this will tend to flatten the texture. Maybe the key light above camera should be filled with side lights, say at 45 degrees, a few stops below the key to recover some of the texture.

Getting the painting in the same plane as the sensor is key too.

Perhaps leave room around the frame and then crop in post, to ensure best sharpness, whatever lens you use. A K-1 will be perfect, as others have said.

Just my pennies worth

[loji]

Thanks all!

The large images (90"x80") would have plenty of space .. I would be 20' back if needed.. It was the smaller images (24"x36") that would have a 6'-10' range.... from the sounds of it, the 75mm would work fine for that. (which is good, I like the way it renders ... similar to my 43 limited)

[tduell]

General question, since I've not done this in digital days - is picture stitching software good enough to use on large paintings?

I'd say yes to that question.
I've used stitching of 4 shots with pixel shift to generate high quality images of paintings.
I use hugin and have never had any issues.

Cheers,
Terry

[swanlefitte]

With the 75mm to get the short side 80" you need 21'
My earlier post thought the long side was 80" and failed to take in the almost 1:1 (8:9) crop vs the 645z crop.

[rdenney]

The standard technique for lighting is to use crossed polarizers, turned one way over the lights and then adjusted on the lenses to eliminate specular reflections from the artwork surface. Large light boxes make it harder, not easier.

The shorter the lens, the more reflections will be a problem, because reflected light will be admitted from a wider range of directions. Short lenses also have more vignetting, which will require correction in post.

I did a similar project using a P67 and a 135mm macro lens. You don’t need a macro lens for magnification, you need it for flatness of field. That said, the 55 DFA is sharp enough and flat enough, despite the reports that it has a curved field, at f/5.6. I wouldn’t go wider, even if it meant requiring art to be moved to a set to be photographed.

Rick “not an easy project” Denney

[BarryE]

The standard technique for lighting is to use crossed polarizers, turned one way over the lights and then adjusted on the lenses to eliminate specular reflections from the artwork surface. Large light boxes make it harder, not easier.


Rick “not an easy project” Denney

To photograph a reflective surface a large softbox is best eg as large a light source as possible - large softbox or scrim up close to the subject. No doubt cross polarizers could work as you suggest, but to photograph a large, textured oil the light sources would likely have to be many and perfectly evenly illuminate the painting. Seems like a lot of extra work as compared with a couple of soft boxes.

[rdenney]

To photograph a reflective surface a large softbox is best eg as large a light source as possible - large softbox or scrim up close to the subject. No doubt cross polarizers could work as you suggest, but to photograph a large, textured oil the light sources would likely have to be many and perfectly evenly illuminate the painting. Seems like a lot of extra work as compared with a couple of soft boxes.

Have you tried it?

I have, and large soft boxes created specular reflections all over the paintings. Scrimming those out scrimmed out all the illumination. It’s hard enough with cross-polarized light.

Oil paintings are often glossy and highly textured. Glass-covered watercolors are easier.

But do what you want. Not my gig.

Rick “not a beginner” Denney

[BarryE]

Have you tried it?

I have, and large soft boxes created specular reflections all over the paintings. Scrimming those out scrimmed out all the illumination. It’s hard enough with cross-polarized light.

Oil paintings are often glossy and highly textured. Glass-covered watercolors are easier.

But do what you want. Not my gig.

Rick “not a beginner” Denney

Yes, Rick I have tried it. It was the method I used when I reproduced my own oil paintings before sale (textured with a lot of knife work) many moons ago and though it was a fiddle the very soft light worked well. As they were my paintings I was ultra picky

Maybe polarization is better, I don't know as I haven't tried it? My concern would be that the smaller light sources would need very careful set-up to maintain an even illumination on large canvases. At some time I'll try this method. I'm rigging up my studio this morning so perhaps I could compare my SBs with a couple of polarized p70s - I think I have some polarizing a4 sheets somewhere ...

As always, there are options, but it is a tricky subject.

Notes:

Ornate frames often used in oil paintings will cast shadows - a grey card on all 4 corners can show uneven lighting. I suppose a post blend of a slightly overexposed image to blend in the edges may be an idea. Removing the frames is better, but this is often not an option.

Getting even illumination, accurate colour, spot-on focus, good alignment (though post corrections can assist here), full colour management, printing etc. and then finally dealing with artists afterwards, which can be the most tricky part in my experience