Stereo variations

On Facebook, in relation to my post on Victorian Stereoscopy, Lena Kallberg commented that she had also enjoyed the on-line course and wished they had dealt a little bit more with the technical aspects. She asked if I knew any good references on things such as what is the optimal focal length for stereo? I didn't know but had done a bit of stereo with several different formats and focal lengths where it worked. I said I thought distance between the pinholes (or lenses if you're in to that kind of thing) might have more effect on the stereo imaging.  So I thought it might be fun to riff on that theme.

I think there's a relationship between focal length, baseline between pinholes, and distance to the subject.  Not sure how to express this mathematically, but you can get good pairs closer up with wide angles, but wider baselines are hard to integrate back into stereo, especially when you're close up. With longer pinhole to film distances, you can take advantage of longer baselines, but you can't be too close to your subject. Not very clear.

The images embedded in this blog are set up for the crossed eye method.  If you want to play along and you've got a lorgnette,  Brian May's Owl, Google Cardboard or an Oculus rift, here's a link to a PDF with them set up for stereo viewers, in the same order they're in the blog.

If you want to learn cross eyed stereo viewing, check this PDF for instruction.

I had lots of 4x5 paper left over from my August workshop, and the paper developer I bought wasn't going to last forever.

I'm not going to get really organized and quantitative.  I just tried a bunch of different things to see if it made a viewable stereo pair, not whether one was best.

About the most outrageous arrangement I could think of was 14oz vegetable cans, which of course would have curved film planes and extemely wide angles. Oddly enough, I tried this before circa Y2K, and I vaguely remember that it worked.

My neighbors ripped out the hedge and part of a fence while we were out of town last weekend, and left it looking really ugly (They plan to put lawn there).

This pair is a little tricky to view, but it works.  (Work on getting the pipes at the top of the fences to align, By the way, this one doesn't work at all with a stereo viewer - see below)

With crossed-eye, the left image goes on the right and vice versa.  Looking at this pair, it seems like there's lot of wall in the right image, and a lot of trees and drive way in the left image.  If you look at the angle of the fence coming out from the house, you can see the left image is on the right and vice versa. I think the cans rotated a little bit without me noticing when I put rubber bands around them to hold to the tripod, so they're actually pointing in a little bit different directions. But where they do overlap, you get a stereo image. By the way, this doesn't work at all with a stereo viewer because you can't vary the placement of the objects in the image the way you can by crossing your eyes.

Tried it again with a little less angular subject matter, and was really careful that they were correctly aligned.

That goes together very easily.  I think it helps that I'm a little farther away as well.  This is the first picture I've done that I could probably pass off as a Victorian stereogram. It's also kind of interesting that without any straight lines in the middle, you could hardly tell this was a curved film plane.

Next up were the one pound Oaks Candy boxes, with the pinhole 2 inches from the paper, pretty darn wide angle. I started with the vertical format with the boxes right next to each other so the baseline was 4 inches. Started fairly close-up about four feet from the baker's rack.

Very 3D.

I went on to try them horizontal.  The boxes are wider than the paper so the baseline is now 8 inches.

I can still get it integrated.  I thought the longer baseline would give me a more prominent stereo effect, but I really don't see much difference and it does make you cross you're eyes harder to get it into 3D.

So now to the 5 inch workshop camera. First with the cameras side by side.

This is an example of an extremely messy compostion with very few cues to depth, but in 3D the pine branch at the top is noticeably closer with the herb garden, the plants along the path, the arbor and hedge at the back of the yard separated in their respective planes.

I'm doing this with a 15 inch piece of board attached to the tripod, and next I put the cameras at the opposite ends, so a baseline of 11 inches.

I think this one doesn't really work. I can get from the herb garden and back into 3D, but can't get the pine branch at the top to come together. When you increase the baseline, you definitely can't get as close as you can when the cameras are closer together.

I've always thought that stereo views of really grand vistas often suffer because distant objects don't have as much difference as those close-up.  Well, telephoto is the photographic solution to getting a closer look at something, and I thought would allow a wider baseline, and end up with better stereo separation.

I got out my 10 inch foamcore camera.  I only had one, so I had to use the cha-cha method, successive exposures with the camera moved between exposures. The house across the street isn't going anywhere, and on an overcast day, exposure and lighting would remain consisent.

First, with a 4 inch baseline as though I had two cameras side by side.

Still works in stereo.  Now out to the 11 inch baseline.

I think I can detect a little bit of an enhancement to the stereo effect with the longer baseline, especially for more distant objects.  I think I can see a little better separation between the house and the trees in the background.  One thing you might not have noticed is that giant rut in the lawn the neighbors made by driving a truck up to the hedge, and I think this closer object is more prominently 3D in the pair with the shorter baseline.

I'm afraid I don't have any succinct summary conclusions after all this. You can use a lot of variations of focal length, and you can use longer baselines with longer cameras, but it makes a difference how far away what you're trying to photograph is.

If anyone knows of mathematical rules that determines all this, or just a better explanation, I'd love to see the link.

ArtsCore Summer Colony

My pinhole workshop for teachers was part of the 3 day ArtsCore summer colony.

To see how I fit into the whole program, and meet the participants, I attended the opening session on Monday morning.

It was held at the Paine Art Center and Arboretum carriage house and conservatory.

This might show a lack of editorial discipline, but here's a closer shot with the sun rising over the conservatory. It was the first time since I retired I had to be anywhere except the hospital first thing in the morning.

Introductory remarks and introductions were held in the carriage house side.

The director of the Art Center just happened to be standing right behind me and gave a few welcoming remarks.

The actual workshop was held in the conservatory.  During the presentation, the art center director was spotlit by a sunbeam from the skylight.  I wonder if he was aware of it?

The exercise used a history/sociology lesson about Cesar Chavez and the Farm Workers Union. A painting by Octavio Ocampo was used to stimulate discussion and the small-group, active-learning, arts-integrating method was to create a tableau vivant with a six or seven word script to interpret his life and accomplishments. The instructor's caveat to think about how you were going to hold a pose for a minute or two sounded like it would be useful for working with pinhole tomorrow afternoon.

Started out on chairs, but with a room full of twenty-somethings, when the active-learning group work started, there was a lot of sitting on the floor.

The morning ended with lunch.

The next afternoon was my turn. No darkroom at the Paine, so we were two blocks down Elmwood Ave. in the Arts & Communication Building at the University.

Tried to have everything ready when they arrived.

It was kind of odd to be introduced as someone who for a long time has had pinhole photography as a hobby. That's what I get for my lack of ambition and conceptual discipline.

Drilling the pinholes and installing them on the cameras.

I spent most of the afternoon in the darkroom and looking at the pictures as positive images on a document camera and discussing them with the participants.  With 23 of them, it felt like I hardly got to work with them at all. When I did get out side, there was only this one group nearby to capture with the Populist.

I got him to get closer.

We had looked through the cameras before installing pinholes to get an idea of the angle of view and had gun site indicators on the camera to determine what was in the frame.  Despite the cameras being about the angle of view of the cell phone cameras they use all the time, when setting up a picture without a viewfinder, most of them seemed to revert to framing the picture about the way how they thought they would frame it with the normal perspective of their eyes instead of getting as close as they needed to with these wide angle cameras. Pre-visualizing the pictures with a wide angle pinhole camera seems to be something that you have to learn to do (...the zen of pinhole?).  I wish I had another day with them.  You can only accomplish so much in a one-day workshop.

It was a brilliant, bright sunny day. I was distressed that there were so many issues with light leaks that had to be fixed.  I think I'm going to get a tattoo that says "The sun is a vengeful benefactor" Anyway, the only picture I took with the workshop materials, in order to test the light-tightness of a camera, was this self-portrait, posed so I could hold it for a minute or two.

All the color with the Populist, .15mm pinhole 24mm from 24x36mm frame.

The black and white with a .5mm pinhole 5 inches from a 4x5 frame.

Developing paper in Caffenol

When the coordinator of the local ArtsCore initiative and I were discussing the pinhole workshop, it came up in conversation that I was developing film in home-made developer and wasn't that kind of a pinholey thing to do. The idea that the ingredients in Caffenol had about the same danger to the environment that the waste water from your clothes washer and dishes have also seemed to work with the theme of the event: "Nature and her Tales."

As I began to panic about what I was actually going to do, I put the idea aside, but I've sort of caught up, and since I needed to practice shooting with 4x5 single shot cameras with paper negatives anyway, I mixed up a liter and gave it a try. (Don't you love it when I mix metric and imperial units of measure).

An immediate impression as I mixed it was that it sure was dark. I've been inquiring of teachers that I knew had conducted workshops and one thing they all emphasize about the response from the students was the magic of watching the image form in the developer.  That's not going to happen with Caffenol.  It's got 40 grams of instant coffee in it. Compared to that cup of coffee in your hand, that's probably about 2 to 4 times stronger. It is essentially opaque. Maybe if you were introducing pinhole to a group that already had experience in the darkroom, it would be interesting, but I'd hate to take any of the magic away from the experience.

But I already had it mixed when I thought of that, so I went ahead anyway.

I didn't do any specific research about it, but I've read a bit about Caffenol and never heard anyone mention developing paper in it.  I remember some internet discussion about using the same developer for paper and film so I thought it would probably work to some extent, but how long would it take to develop it?  Would it stain the paper (it really doesn't stain film)? Would you rate the paper at the same ISO rating? What kind of grey scale would you get?  The biggest caveat about Caffenol was that it tended to create background fogging on films rated 400 or over. I didn't think that would be an issue with paper.

I was using Arista RC Grade 2 Semi-matte, rated at ISO 5 in the f250 workshop camera.  It was a sunny day, and direct sun seemed like an exposure I could repeat fairly reliably for comparison. I even metered it and it agreed with Mr. Pinhole and my standard chart for paper.  A minute.

Somewhat randomly, I decided to start with 2 minute development.

The first negative looked pretty good, but it struck me when I first looked at it that it was a bit underdeveloped. The blacks looked like they could get darker but, I could get a pretty good scan from it.

The next two negatives seemed a little lighter than I'd like, but I couldn't tell if it was a case of a difference in exposure or something to do with the development.

The fourth picture, I decided to go with what I thought would be a lower contrast subject. It was in the shade so the exposure was a lot longer, but I didn't measure it, I just guessed (based on the standard chart) that it was about three stops lower. After two minutes in the caffenol, I pulled it out of the developer and it looked really thin, and although I tell everyone to wait to judge a negative until you look at it in room light, I decided to see if more development time would bring out more detail, so I left it for another two minutes. The extra development time definitely made a difference. The blacks are blacker, but I thought I was starting to see staining on the unexposed portions.

I still got a pretty good scan out of it

.

I realized that by taking a photograph and developing it and then going back out when the lighting conditions were changing, I wasn't going to get any real comparison.  So I loaded three of the workshop cameras and took three successive shots at the same exposure, and then developed them for 2, 3, and 4 minutes.

The two minute does look a little underdeveloped to me.  The three minute seemed pretty good, and the four minute seemed to have even better shadow detail, but the highlights seemed to getting a bit blocked up.

My best scans of the three.

The first is a little lacking in shadow detail, but despite the differences in the negatives, the last two look pretty good to me. If I was going to do this regularly, I'd probably pick the middle one - three minutes.

So, can you develop paper in Caffenol? Yes. Does it affect the response of the paper? Not really too much. Does it stain the paper?  Yes, a little, and the longer developments showed a little more staining, but it still wasn't too bad, and might have controlled contrast a little.

I'm still not going to use it in the workshop in order to let the participants watch the image form, but it would work.

Workshop camera

  For the teachers workshop I'm doing in August, I considered several camera designs, but I ended up deciding to use the trusty 4x5 inch format, 5 inch long camera I've used in almost all the workshops I've done. Before Ruth Thorne-Thomsen gave a workshop at the small liberal arts college on the praire where I was working, she sent me a handwritten sheet with illustrations (which I really wish I still had) with the directions for how to build it so participants could make it ahead of time. It's essentially the same camera she had used for the work she has in major museums (except hers was covered with several layers of tape when I saw it.)

The one on the left was made by a 6th grader who accidentally took home a camera I made instead of his own. (They do look a lot alike).

Yesterday, I picked up the card stock for the August workshop, and made the one on the right.  (Very grateful to Jim Evans of the Art Haus for cutting it into 5 inch strips for me). I love the professional black body look. I haven't made one of these since 2006.  It took me a little over a half hour.

It's basically a 4x5x5 inch box with one end open, and a back that fits snugly into the box. Most of the people whom I've made these with get it light-tight on the first try, and I did too. (Looks like the piece of paper is a little too big.)

If you're interested you can read all about it and how it's made starting on page 5 of my 1991 Guidebook for Teachers.

I chose this camera for a lot of reasons. I don't have any contact with the participants until the workshop happens so I can't get them to bring existing containers, and we don't really have time to mess with lightproofing a bunch of different boxes.  It's long enough there's not much vignetting. I'm kind of a fuddy duddy about curved camera backs. Particularly for beginners, the curving geometry really puts a stamp on the image which I often find distracting from the subject and composition.  Give me a rectilinear, flat film plane any day. It's also very simple to vary the length of this camera, although we won't have time to do that in this workshop.  Rookies often can't previsualize well with extremely wide angle cameras, so the 5 inch length minimizes this, about equivalent to a 35mm lens on a 35mm camera. (Still pretty wide angle though.)

I drilled the pinhole with a .5mm #10 needle in a piece of a Leinengkugel's beer can.  Looks like it's got a little bit of a burr at the bottom, but I was afraid I'd bend it if I got too aggressive with the emery paper.   It's very close to Mr. Pinhole's optimum for this pinhole to paper distance.  That makes it f250. A little slow with sunny day exposures about 1 minute, but I've never had a problem with people not being able to deal with long exposures.

Another thing I haven't done for ten years, except for a few exposures about a month ago, and a few experiments yesterday with a couple other cameras,  is take pictures with black and white photographic paper, so I loaded it up and went out and took some photographs.

Here are some irises that got knocked over by the rain and are leaning on a wire plant support.

Sarah discovered these volunteer grass lilies that some bird apparently planted in the herb garden,

And a peony, also pushed down by the rain conveniently firmly supported by some apparently stiff weeds below it. Since it's pink, I expected it to be darker with photographic paper insensitive to red light.

Looks like it still works. Hope we have a nice, still, sunny day like this when August rolls around.