Tuesday, January 15, 2019

Eclipse Lunargraphy and other trails

A couple of things prompted this post. Recently on the Pinhole Photography Facebook group, Janet Neuhauser posted an all night exposure of the trail of the full moon and noted that it didn't pick up anything but the moon's trail. The other thing is that a total lunar eclipse will occur next Sunday night that's visible from all of North and South America.

In April 2014 there was a total lunar eclipse in the wee hours of the morning. I couldn't bring myself to stay up all night to see it. I just put The Populist out after dark and before twilight began the next morning, closed the shutter. I never saw the eclipse at all.

That night Mars was shining at magnitude -1.4 and pretty near opposition so it also passed all the way through the scene during the night. In the full frame you can just barely see it. It's easier to see in a close up detail.

This image is also notable because even in eclipse, the moon was bright enough to be recorded and the reddening is clearly visible. The extremely overexposed full moon trail on the little 35mm negative shining through the pines also makes for a dramatic image.

Encouraged by my success in April, I tried again later that year in October. This time the moon set while it was still in eclipse.

A year later at the end of September there was another total lunar eclipse that began not long after moonrise. I decided to go over and sit in Menomonie Park to watch it. I thought maybe I could get a reflection of the trail in Lake Winnebago. The eclipse was just beginning its partial phase before the sky was dark enough to open the shutter

Duh! Angle of incidence equals angle of reflection. After the moon rose a bit, the reflection was no longer bouncing back to my position on the lake shore. This is a fairly severe crop of The Populist's 35mm negative which really emphasizes the overexposed full moon trail. The film was Walgreen's 400 film so it was even more blown out than the earlier moon tracks done with the 200. The red color of the lower lobe is curious. I would ascribe it to haze and light clouds but it doesn't look like that in other pictures done that night.

I also had the 6x6cm Glenmorangie Evil Cube to see what it looked like with a larger negative.

This was with Portra 160, slower than the film in the Populist and it's about a stop slower camera. So the trail is less extreme and there's just a bit of a glow reflecting in the lake. Without the overexposure of the moon's reflection near the opposite shore, it captured a few lights over in Calumet County.

I had my 10x50 binoculars along to entertain myself during the long event. I took advantage of the darker skies and just scanned around the sky. A notable memory was my accidental discovery of Uranus just few degrees from the moon (verified by Sky Safari). It's hard to believe no one noticed this kind of odd fuzzy green star moving around before William Herschel.

This next image is not an eclipse, but again referencing Janet's post on Facebook, I was shoveling snow one morning before dawn with the moon and an extremely bright Jupiter setting in the west. It was also near opposition, shining at -2.5. As usual The Populist was in my pocket. I set it on the big pile of snow next to the driveway and opened the shutter while I finished shoveling. In addition to the moon trail, I also picked up the trail of the giant planet.

Twilight was beginning so although it was brighter than Mars during the eclipse, it's not much clearer in the whole negative but you can see it in a full resolution detail. The beginning of the moon trail looks like it might be the shape of a waxing crescent but it had to be full to be setting just before dawn and I can't really explain why it looks like that.

I wasn't the first one to do a lunar eclipse pinhole photo. In 2007, on f295, a participant with the nom-de-internet Monophoto posted a lunar eclipse image. A year later, Gregg Kemp posted a picture of an eclipse in his gallery of landscapes with moon trails. Working on this post, I also found a gallery of Lunargraphy by Csaba Kovacs.

These weren't my first experiments with pinholing the moon. On the Pinhole Visions forum, therefore prior to 2004, there was an occasional special assignment topic. The theme for one of these was "motion" and I remember thinking it would be cool to do it on the largest scale possible. With a 4x5 camera and photographic paper I did an all night shot of the moon rising over the house. I no longer have that image, but a decade or so later, I recreated it with The Populist, this time adding interest with a Mustang in the foreground.

The current prediction for the weather next Sunday is mostly sunny so I may get another chance at a total lunar eclipse. (Although it hasn't been clear for more than an hour or two since mid-December.) Winter in Wisconsin is usually a pretty good time for pinhole lunargraphy. The sky will be completely dark by 7 PM and stays that way until at least 6 AM, even facing east toward the rising sun. At mid-eclipse the moon will be almost due south and quite high in the sky. Venus rises at 3:54 AM at magnitude -4.4 and Jupiter at magnitude -1.8 rises at 4:40 AM so they might be at least partially within the angle of view as well by the time I have to wake up and close the shutter.

Later edit.

I made three images of that eclipse in 2019

A stereo image with a 60mm long camera with two 6x6cm image chambers. (Set up for crossed eyes)🧐

A panoramic image with two side by side 35mm Populists pointed in slightly different directions.

And one with a wide angle 30mm pinhole to film camera on a 6x6 frame.

In 2020, I finished Worldwide Pinhole Photography Day with an exposure of the crescent moon and Venus setting in the West.

Friday, January 11, 2019

Diffraction Action: Six pinhole sizes at two distances from the image plane

One of the never-ending discussion points of pinhole photography has to do with the “optimization” of the size of the pinhole at a particular distance to the image plane. A basic assumption is that the bigger the pinhole, the bigger the spots it transmits and hence the smallest feature it can render.  Another basic idea is that wavy photons can turn a little when they squeeze through a too small hole and create a predictable pattern of fogging around each point. The visual effect of all this is usually described as sharpness.

Right away, I want to get out of the way the idea that sharpness and best are equivalent. Every pinhole has its unique character. Pinholes far from optimal can be used as artist’s tools, as well as other sharpness factors like pinhole shape and movement of the camera and subject. Sort of like the difference between a sharpened pencil and a stick of graphite.

But what does all this really look like? Let’s find out.

As with my experiment with pinhole materials, my subject was a little tableau under the fluorescent lights in the basement to remove lighting as a variable. In order to eliminate the variable of my clumsy craftsmanship, as well as getting out of drilling six precisely sized pinholes, I used Gilder Electron Microscope apertures. In my opinion they’re as good as pricey laser drilled holes. I wanted to try two different distances from the image plane and only wanted to invest one roll of film for my curiosity so I mounted (couldn’t get out of that) six of them, .075mm, .15mm, .2mm, .3mm, .4mm, and .5mm.  I used the 100mm and 45mm fronts for the Variable Cuboid to make it easy to switch the distances and taped the pinholes on the outside of the shutter to make them easy to change.

The film is TMax-100 developed in Rodinal 1:50. I used Pinhole Assist’s spot meter function to measure the cardboard top of the camera in the picture which looked to me like Zone 5 and went with the recommended reciprocity correction. I’m a little surprised the exposures came out so uniform, although there is a little variation and the scanner software has to put its two cents in. I tried to adjust them to match. Also, partly just to get out of it, I’m not going to touch up the dust spots, which will give some veracity to the sharpness of the scans but which creeps me out a little bit.

Don't jump over to Mr. Pinhole to see what the optimum is until you've looked at the pictures.

First the 45mm. Looks like the pinholes didn't get exactly centered in the opening.

.075mm pinhole, f600

.15mm, f300

2mm, f225

.3mm, f150

.4mm f112

.5mm, f90

Looking at the full image, it's hard to tell the difference between the .2, .3 and .4mm holes.

How about a detail at full resolution - here's some text and the label on the diagram in the left column of the encyclopedia. Each segment is 180 pixels wide. The full negative is 5000 pixels wide.

It looks to me like the .2 is just slightly more detailed than the .3. It's really obvious how diffraction reduces the image quality with the smaller pinholes.

Mr. Pinhole says the optimal diffraction is at .283mm, so maybe my habit of using smaller than recommended pinholes isn't so bad.

How about at 100mm?

.075mm, f1333.  Well, this is disappointing. This was a six and a half hour exposure. When I made the switch, I set down the 45mm front next to the scene. For some reason which escapes me now, I went down there to get it and seem to have managed to bump the tripod leg reaching over. There goes that data.

.15mm, f667

.2mm, f500

.3mm, f333

.4mm, f250

.5mm, f200

This time the .3 and .4 images don't look all that different. Let's go to the details.

This time I have to give it to the .4, but not by much. Mr. Pinhole says .422 is optimal.

One of the things that got me going in my post a couple of weeks ago was a comment that said, even with an optimal pinhole, the image is always going to be sharper with a shorter distance to the image plane, so let's bring back the 45mm set and maybe you can get both sets on the screen at the same time to compare them.

Even though I tried to capture the same field of view, there does seem to be some difference in scale, but I can't say the sharpest of the 45mm looks much sharper than the sharpest with the 100, even though the pinhole is half the size. Makes me think that diffraction is a bigger contributor to sharpness than the size of the dot projected by the pinhole. High f ratios and long exposures are better reasons to avoid longer cameras than sharpness.

Since the theme of this piece is diffraction, I thought it would be appropriate to put one of those "points" of light in the scene.  There was a lamp inside the camera shining through its pinhole.

A full resolution set at 45mm.

and at 100mm.

From this comparison, it looks like you can get away with a smaller than optimal pinhole close to the image plane, but diffraction seems to make that a bad bet for longer cameras. Maybe a little bigger pinholes on Long John Pinhole would be a good idea.

It's interesting to see how the disks vary on either side of the optimum and it's hard to tell the difference between too small and too large.

Another thing that the equations say is that the distance to the subject also affects diffraction. Where the shutter obscured part of the scene, that edge is rendered more sharply with the .075mm on the left than with the .3mm on the right.

My main take away is that there's a pretty good range around the optimum where it's going to be really hard to see the difference. If you're within a tenth of millimeter, it's probably good enough, so don't get too hung up about it and concentrate on all the other things that make a good photograph.