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 get 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.

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.

.3mm Gilder aperture
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.

Tuesday, December 25, 2018

from f295: My first camera from a Scotch Box.

f295 was an international discussion forum begun and administered by Tom Persinger. Originally just about pinhole photography, it expanded into all kinds of alternative methods. It was active from 2004 until 2015 but it remains on-line. Recently it disappeared from the web for a few days, and that prompted me to decide to reprise some of my favorites here at Pinholica, for backup if no other reason. 

Bottles of Scotch come inside some pretty well made boxes. I've made cameras out of a Glenlivet box, a Glenmorangie box, and one I made for my son from Macallen as a Worldwide Pinhole Photography Day gift. (He and his best man toasted with a wee dram of Macallen before his wedding the previous autumn).  This is what started it all. Posted under the title "Last of the year," on January 3, 2006.

My wife gave me a bottle of Scotch for Christmas. She said she chose Glenmorangie because she thought the box it came in (3.5" x 12" cylinder) would make the best pinhole camera. How can you pass up a challenge like that? The only matte finished paper I had was already cut into 4" x 5" pieces so I taped three of them together. Two minute exposure (very gloomy day), .49mm pinhole, about f 128 (I took the pinhole off an old workshop camera) A bit of burning and dodging in photoshop to correct for center to edge exposure differential.

I got another Macallan box last night.  Happy Yuletide! Did you get a present in a box you could make a camera out of for Worldwide Pinhole Photography Day?

Friday, December 21, 2018

Pinhole distance role reversal with the Variable Cuboid.

With the first roll through the most recent iteration of the Variable Cuboid, I primarily used the 100mm front for exteriors and the 35mm for interiors.  To do due diligence, this time I switched and used the longer front inside and wide-angle out and about.

I started with a walk around the neighborhood. The Glad Tidings Tabernacle is just around the corner from my house. I've always liked the simplicity of the structure and the large plain windows. Looks like a little bit of curvy film on the right there.

The Centennial Inn assisted-living facility is nearby on Main St. Originally built in 1902 as the Ladies Benevolent Society Home, it looks shocked by my temerity.

I've recently heard a lot of discussion about how the surprise element of seeing what you've actually photographed was one of the delights of pinhole. The bit of curvy film in the church image and the pointy stretched-out corner of the Centennial Inn are some of those impossible-to-really-preview-in-your-head situations. Here's another with our big back yard hydrangea. The camera was actually touching the nearest branches and virtually the whole tree is in the picture. You can barely squeeze between it and the garage but here it looks like there's plenty of room. The garage looks smaller than the shrub. Your brain just won't let you see it like this even though it's kind of what's projected on your eyeballs and they're curved as well. But the pinhole reveals all.

The weather was exceptionally gloomy. Back inside with the 100mm mounted, I pointed the camera at Buddha's corner by natural light and left to go across town to the farmers market, do a little shopping and have lunch. After we got back, I forgot to close the shutter for another 20 minutes.

The gloom persisted. Here's a nice academic study of some silver by artificial light.

Moving on to the glassware. Amazing how still those pull chains on the lamp are. We had lunch a few feet away during the exposure. Check out the refraction of the base of the lamp through the clear decanter.

The sun came out for a while one morning.

I finally decided to defy the gloom, put the 35mm back on and just go out and wait as long as the exposures took.

I've had my eye on this building for some time. It was recently remodeled and houses the alarmingly named marketing agency DealerFire. There's a little walled garden behind the building for employees to hang out in, so I had a nice place to sit and wait 8 minutes for the exposure somewhat out of the wind.

I've been waiting all year to photograph this delicious grid of reflecting windows. The street in front of it and half of downtown was under construction all summer. You can see the plastic covering a ramp they poured just before they finished.

The nifty grid and the fresh concrete were the first thing that caught your eye, right? You may have noticed that I occasionally suffer from curved film. It happens because the film transport in my cameras can be a little tight and you have to loosen the supply a little bit and then take it up on the other side. This can push film out into the image chamber which you may have to retighten around the supply to pull back up against the image plane. I do like perfect grids and I do try to retighten the film but sometimes I forget. It was cold and windy. This is a disaster with a film camera but with pinhole it's just kind of funny. I'm afraid to admit that I'm beginning to like these random distortions. I've always avoided curved film planes because to me they stamp a standard look on the composition but this random stuff is kind of fun. I'm not sure what should be done about it. Maybe be more careless winding the film?

The 35mm front has .25mm pinholes. All except the tree were done with the rising pinhole.

The 100mm front has .35mm pinholes. All these were with the on-axis pinhole.

TMax 100 in Rodinal 1:50

Friday, December 7, 2018

Was Lord Rayleigh talking about sharpness?

This all started because of a comment in the Lensless Podcast Facebook group that a longer distance to the pinhole always results in a reduction in sharpness.

What he means is, according to physics worked out by John William Strutt, 3rd Baron Rayleigh in the 19th century, the farther the pinhole is from the image plane, it will take a relatively larger pinhole in order to minimize diffraction. A bigger hole will result in a loss of sharpness. (Perfection of the pinhole is also a significant variable here. Think of it as a lot of tiny holes on the edge of the pinhole that the photons have to squeeze through.)

I've always preferred a smaller than optimum pinhole for my longer cameras.

Everybody checks Mr. Pinhole’s calculator for the optimal results of these equations, and everybody thinks of this in terms of focus.

That started me on a thought experiment.

These equations predict the formation of an Airy disk around a point of light.

.15mm electron microscope aperture, 24mm from the image plane, about 5m from the subject.

Even the best optics in focus form an Airy disk determined by some algebraic gymnastics on the wavelength of light. The Hubble Space Telescope forms an Airy disk. Billions are spent minimizing them. Even with adaptive optics it’s still there, it’s just very, very small for a perfect 30 meter telescope mirror.

This is different from circle of confusion which is associated with depth of field and focus. With a pinhole aperture, circle of confusion always gets greater with a bigger hole. Diffraction varies on both sides of “optimum.”

The Airy disk is still there out of focus, it’s just more diffuse. With a pinhole, it’s just always there, no focusing is going on. It will vary in brightness and radius as a certain size pinhole moves toward or away from the image plane or from a source, will be least bright at some point and the disk itself will vary in some predictable wavy pattern, always rather less bright than the point itself.

How does this really impact the image?

Think about your average American holiday image.  How many point sources of light are there when you have a decorated tree in the picture? An infinite number of course.  Every point in the image is a source. They all have an Airy disk. You just don’t notice them unless it’s a picture of a mini-light, which is also overexposed anyway, so its Airy disk is going to be a whopper. The Airy disk around each theoretical point of the soft glow of your kid’s dreamy face isn’t probably going to rise to the level of the film’s sensitivity, and if it does, it’s a soft glow, it’s not out of focus. Sharpness is determined by the size of the pinhole. At extremes, diffraction reduces the contrast between all the points and all the the disks to unmanageable levels, and it’s not going to be happy with overexposure.

That's assuming you could get the kid to sit still long enough for a pinhole portrait by the light of the Yule decorations with a smaller than optimum pinhole. Motion blur is something else again and like circle of confusion is determined by light acting like a particle which allows us to make pinhole images. Diffraction is evidence of it’s wavelike behavior that gives pinhole some of its unique quality and also affects all optics. Happy Holidays.

The pinhole holiday is April 28 in 2019.

Sunday, December 2, 2018

From f295: They're responding

f295 was an international discussion forum begun and administered by Tom Persinger. Originally just about pinhole photography, it expanded into all kinds of alternative methods. It was active from 2004 until 2015 but it remains on-line. Recently it disappeared from the web for a few days, and that prompted me to decide to reprise some of my favorites here at Pinholica, for backup if no other reason. 

I recently listened to the Lensless Podcast with Nicole Small speaking about her self portraits and it reminded me of this. Quoting Frank Zappa I had done a post of closeups of vegetables, and followed up a week later with this mostly wordless essay under the title "They're responding" on February 12, 2008.

I can feel it.

About a year later a local art collective organized The Oshkosh Triennial juried show where ten regional artists were featured with six works each and they picked me!  The last picture with the red pepper was one of the images in that exhibition.

These were all done with The Populist, .15mm pinhole 24mm from 24x36mm frame.