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.

The evidence

In order to experience using a tripod, you have to shoot some film. Here's some of the data for my tripodology study.

Occasionally my bike rides take me on the Wiowash trail next to Highway 41 on the causeway over the Fox River and Lake Butte des Morte. In the center where it opens into a bridge, there are trails that lead down to the water's edge. I'd been down the one on the north side but until now had never gone down the one on the south. I discovered that it goes under the highway and over to the other side.

There was a boat full of fishermen just off shore sitting relatively still. I started with the PinRui flexible tripod wrapped around my bicycle handlebars.

Turning around, the view of the bridge itself.

Between 1980 and 2011, for state projects that are primarily for access by the public, there was a Wisconsin law which mandated that a small percentage of the construction budget be used to commission art work. Apparently they felt people accessing the bridge would be going by boat. Although the bridge has some decorative railings on top, I never knew these graphics were down here.

Walgreen's has decorative plantings around their parking lot. I had walked over so no handlbars to wrap the tripod around and nothing else handy. I had to put it down on the ground to capture this burning bush.

Another autumn show-off, again from about seven inches off the ground.

I switched to the ProMaster when I went out to rake leaves. Here I'm holding it against the trunk of our large pine.

Still held up against the pine tree but looking the other way up Central St. I thought I felt the camera slip around so I tried three exposures to hold it still. They all look about the same. This is the last one that I thought wasn't moving. The slight movement does give it a little extra pinholiness.

A view with the tripod on the ground, so no camera movement here.

An unsuccessful attempt at Footography.

I went on a bike ride with the Amazon. Can't wrap this one around my handlbars. Here it's held up against an oak tree.

Held up against a fence at the Yacht Club.

This happened to be on Halloween. It may look like the tripod is on the floor but it's held up against a column on the porch to get it just a little higher in order to look this guy right in the eye. The fluting provides some nice bracing to keep the hard plastic feet from sliding around.

This summer the arbor was covered with morning glory vines, although few morning glory blossoms. The first frost gave it a bit more of a Halloween appearance. The tripod is sitting on the gazing ball.

It is possible to hold the camera motionless held against a smooth wall but it takes some concentration.

I suppose if it were listed in a cooking supply catalog it would be called a counter top tripod.

It doesn't make any difference what the tripod is if you bump the subject during the exposure.

All with the Populist. .15mm pinhole 24mm from 24x36mm frame on Kodak Gold 200.

Omnia Pinholica est sustinetur in tres pedes

January 2024. When my university retiree account disappeared in 2019 with a new change in policy, the pictures I uploaded to this blog while logged into that account disappeared. I'm replacing those original pictures pictures with some current documentation of the fate of the discussed items, with new comments in the picture captions.

An infamous subject of the crown has assailed the assertion in my manifesto espousing the empowerment endowed by a tripod in the full and free expression of stenopaeic photography. I reaffirm my insistence on the inalienable right to point my pinhole at and from where I find it to be self-evident and to provide secure freehold for all film.

When in the course of a holiday's events, the resources to maintain stable practice became insufficient, it became necessary for this pinholist to go a little mad and to thrice seek to right this deficiency in the marketplace.

[picture of three tripods]

I got the ProMaster TRM-1 Mini Tripod on the left at Camera Casino. From the internet, I got the Amazon Basics Lightweight Mini Tripod in the center and on the right, with a name longer than the tripod, the PinRui Flexible Octopus Style Mini Tripod Stand Kit Universal for Cellphone Smartphone and Sport Action Camera. (Hmmm. PinRui. I wonder?) It also came with a phone adapter, a bluetooth shutter remote and another clamp that I can't quite figure out.

Of course I was doing this to get over my grief at the loss of my little ProMaster folding tripod. It was a workmanlike little support and its defining feature was that it folded into a flat little slab about the size of a TicTac dispenser. It would fit in almost any pocket. You could sit on it without discomfort. I hadn't realized it until it was gone, but it's rubber feet were a critical attribute.

My broken tripod

No one seems to make tripods that fold flat like that any more. When I dropped my film off at Camera Casino, I thought I'd found a replacement, the T2 Mini, again by ProMaster, although it's a little longer than my old one. (I took this picture to use up the film in The Populist before I dropped it off.)

When I got home I discovered that although it was nice and flat, it's head only tilted back and forth, no swivel, no tilt to the side.  Not going to work for me. I also got one of their little gag keychain tripods that might hold one of my 35mm cameras, but the head doesn't lock and it falls right over. 

I went through the pile of the keychain tripods and found one with a head that's stiff enough to hold a 35mm Populist. I carry it as a back up and it occasionally gets used. It's really easy to fit in your pocket.

When I went back to pick up my developed film, I exchanged the T2 for the TRM-1. They only had two colors in stock - red or blue.  Red would attract more attention so I got the blue.  

A leg came off pretty quick and I got a new one, but it's never been my favorite.

In between the visits to Camera Casino, I had already bought the other two on Amazon.

So what peculiarities maketh the vision of the pinholist stir and ease the trembling of the illuminated plane? 

General Pocketability

It seems like an odd place to start, but I carry one of these with me almost all the time, all year round.  It's an easier business when it's cold enough to wear a jacket but pockets in Levi's are not made to be particularly voluminous, probably for visual reasons, which I admit to noticing in the mirror.

  

It's about a tie between the ProMaster, a little shorter, and the Amazon, a little smaller circumference.  The PinRui just barely fits in a back pocket and it makes a more noticeable budge, although with it's mostly foam covering and conformable shape, it's not that uncomfortable to sit on.

Weight is a factor in this pocket game. This time the Amazon and the PinRui tie at 54 and 55 grams. The ProMaster is a distant third at 98 grams. That's still not a lot of weight though. They're all almost unnoticable in my pocket. The heft of the ProMaster could be an advantage on a breezy day.

Durability and strength

I'm going to be pressing these things against hard surfaces and frequently sitting on them. It seems a little premature to evaluate durability, but I think we can make some assumptions. The ProMaster wins hands down. Except for the handle on the socket clamp and the feet, it's All Metal. A lot of the Amazon is plastic. It's legs are held on a metal plate with screws so someone thought about it. I'm a little skeptical of the PinRui. It's covered with foam. I've seen foam tear and deteriorate into crumbly bits leaving an ugly and sticky residue. I don't know anything about metal fatigue but how many times are those legs going to flex before they break? Let's say its going to get it a good test. One of its legs came out of where it attached to the top but it pressed right back in and seems to be staying there. That flexible wire probably won't maintain a thread to screw it in with.

I've had generally good luck with the folding-flat tripods. I've only had two break in the last ten years. My old little ProMaster was 7 years old. 

They're cheaper than most sandwiches so cost comes before utility and life span in their design. They're between 5 and 10 dollars on-line. Not a significant investment to replace but it's irritating to have something come apart in the field very often.

Maximum height.

I like to get the camera at least a little off the ground or a table's surface. The ProMaster has three section legs, the Amazon two, and the PinRui's legs are just one piece.  

The ProMaster wins, even though it looks like I pushed two of it's legs in a bit futzing with it. I can handle that as long as I get the camera level. The PinRui comes in second, but at the expense of narrowing its base, ergo stablility. The Amazon has a greater angle of extension and is really spread out when extended like this. Stable, but covering a lot of real estate.

Minimum height

Yes, Justin, I know I can put the camera right on the ground. I usually want to get this low to point at something on the ground and occasionally to point up and into a plant. The ability to keep from falling over when the camera is tilted 45° down without getting its legs in the picture is also a consideration, which they all passed.

The PinRui squashes down to the surface the closest. It also gets points for being continuously variable on those bendy legs. It's pretty spread out and stable. If your surface isn't that big you can bend the legs down to clamp over the edges. Notice the angle of the ProMaster's legs. That knurled band just above the legs screws up and down, changing the maximum angle so there's some fine tuning on that one too.

The head

The ball and socket must be adjustable on two axes and hold the camera in place for the picture. 

The ProMaster and the Amazon have the same general design, a cylindrical enclosure with the clamping bolt at the bottom. The ProMaster's head also rotates when it's loosened. On the Amazon there's a phillips head screw between the legs that holds them to the head. If that screw is loose the head will swivel around but is useless that way unless in a vertical position. In addition, you have to make sure that when that screw is tightened, the gap in the head, which allows you to tilt all the way over 90°, is aligned between two of the legs. Otherwise they'll get in your way when the camera is pointed down or you're holding it against a wall. These heads also seem to be either loose or locked with no variable drag. The PinRui has a plastic cup containing the ball with a clamp in the back that squeezes it tight. Even with the clamping bolt completely loosened, it has enough drag to hold my two ounce cameras in position. It's tempting to just leave it loose but once the nut came off the bolt in my pocket, so best to tighten between photographs.

Holdability against a vertical surface.

Just as often as I set the tripod down on a horizontal surface, I hold it against a wall or light post.  It's necessary to still be able to get the camera level and pointed at whatever angle I want.

It seems they all past the test but it was much easier to hold the PinRui against the wall than it is the other two.  It comes down to two things. The lesser is that the legs of the ProMaster and the Amazon both flop back together when held up like this and you have to adjust your grip to hold them at maximum spread.  The PinRui, while you can't press too hard or it will bend, has legs that stay where they're put until acted upon by an outside force.

The more important thing that makes the PinRui better at this is something that hadn't occurred to me before - the feet. Even though I had dealt with slippery feet on an antique wooden tripod in the past.

My old little ProMaster had feet of hard rubber. This ProMaster and the Amazon have feet of hard plastic. They're almost impossible keep from sliding across a smooth surface, especially when you're putting a little force on it to hold it in place in a clumsy posture. I tried to modify the ProMaster by wrapping the feet with a couple layers of black duct tape, which helps a little but it still takes concentration to get it to hold still. The PinRui's feet are medium hard rubber with a high coefficient of friction that doesn't slip and combined with the light weight is easy to hold in place even for a long exposure.

Span

This one is rarely used but sometimes, the most stable place is spanning a gap, between two branches or over a bumpy surface.

The ProMaster can bridge a slightly broader expanse but something tells me the feet of the PinRui are going to make it sit more stably in that kind of a situation.

In summary, each of these has unique advantages and I'll probably use them all at some time.

The Amazon

The lightweight Amazon's major advantage are it's good looks. You could pull it out of your Chanel handbag at the gala ball and it would fit right in. It's small and light and probably the least likely to create an unsightly bulge in your suit jacket pocket. It's good enough and if I could fix the issue with the slippery feet, it would be adequate in most situations.

The Amazon turned out to be the only one of these that survived. It was my go-to desktop tripod for several years.

The ProMaster 

It's noticeably stronger and better engineered and with the rotating head and the variable angle legs, a lot more adjustable than a lot of desktop tripods.  

I wouldn't recommend it but it's just strong enough to hold this N50 with a body cap if you don't try to tilt it too much. It falls over with a lens on it.

The PinRui

The flexible legs make it completely different from any other tripod I've had, and I have to admit I'm having fun fooling around with it.

The legs of this one couldn't stand up to the use and came off several times until I couldn't get them inserted any more. I repurposed the head attaching to a clamp with rubber bands.

I've always been tempted by Jobo's Gorillapod for the capability to attach to things but it's too big and heavy for everyday transport in a pocket. This one does pretty much everything a regular desktop tripod does, plus everything you could possibly imagine. Those legs wrap around things and clamp to some really odd shapes.

That ability to come out of my pocket and quickly wrap around the handle bars is something I will use a lot.  Strapping and unstrapping a full tripod to a bicycle is annoying and the rails, benches, trees, signs and tables I depend on aren't always nearby. This gives me some good height off the ground and it only takes a second to deploy it this way.

The foam covered, segmented, bendy legs are kind of odd looking and impossible to get perfectly straight ever again. My anal-retentive inner graphic artist wants to try to straighten them but I'll get over that.

I eventually got the smallest version of the Gorilla Pod. The joints are a little iffy and it comes apart if you try to wrap it around things, but the part can be popped back on.  The magnetic feet are really great if you're on an iron or steel object. Not really something I can depend on.

Our lovely models for this pageant have been the PrePopulist on the ProMaster, The Populist on the Amazon and lately made just for these photographs, a new Understudy for The Populist which is now loaded, in my pocket with the PinRui, continuing our investigations in tripodology.

And yet I can exercise my free choice to place the camera directly on terra firma.

My current favorite, and likely to be for a while is this little Dorr which nearly duplicates the features of the ProMaster whose loss started this whole thing, but made out of a little better material and solid screws.

Roadtrip: The other side of Lake Michigan

Since most of our stops were in large cities, we thought a little lakeside resort experience would ease us back into normalcy.

 Previous episodes:    Rock and Rochester      Blue hills, blue water, and black humor       Art is what you can get away with in Western Pennsylvania

Until I was 11 years old, I lived in South Bend, Indiana. About twice a year, we would go up to Warren Dunes on the shore of Lake Michigan to frolic in the waves and the towering dunes. Sparked by that memory, Sarah began collecting a series of Art Deco posters that are in regular rotation in our kitchen promoting Warren Dunes as a getaway from Chicago on the South Shore Line railroad. We decided to make it our last featured destination.

I tried to find accomodation along the lakeshore, and specifically not a chain motel in a cluster alongside the interstate. It was a Saturday night and everything in our range seemed booked with weddings but one of them had a second smaller hotel linked to from their web site. It seemed just the thing, and they had rooms available.

The Gordon Beach Inn, "a casually active, rustic and historic 1920's Inn."  I'd also throw quaint in that description. Both of the men who staffed the desk could easily have been cast in Bob Newhart's innkeeper role, but were much more cheerful. There are separate metal keys for the rooms and the outside doors which they secure at 11:30 pm on weekends. They sent us a letter in the mail confirming the reservation. It was very nice.

Variable Cuboid with 45mm front  - rising pinhole

I had to get a picture of the back porch in the evening sun. My Aunt Stana's cottage on Christy Lake looked exactly like this.

Variable Cuboid with 45mm front - rising pinhole

The Inn is about two blocks from the lake but they have their own private beach accessed by a narrow path between two private homes and a stairway down the bluff. Until the sky cleared while we were on the Ohio Turnpike, it hadn't occurred to us that we would be there for the sunset over Lake Michigan.

I hate to get all Claude Monet about this, but it was notable how the light changed minute by minute as the sun went down. I began with Long John Pinhole to concentrate on where the sun hit the horizon.  It was cloudy in that direction, but The Photographers Ephemeris gave me the accuracy to point with the narrow angle camera in case the sun peeked out. Low tech photography, ya know.

The sun never actually appeared through the clouds, but the sky kept changing. f362 isn't really where you want to be when the light is fading, so I switched to the Variable Cuboid.

A more shoreward view

I think the shoreline, the reflection of the sky in the moving water and how the pinhole records that last wave are more interesting than the sky.

I switched to the Populist to see if I could keep following the more intense visually, but technically dimmer show.

The display just kept getting more intense. We had dinner reservations for our last night on the road so about twenty minutes after the sun had actually set, we headed back toward the hotel. It must have been sunny in Wisconsin because when we got to the top of the stairs, the underside of the clouds was illuminated creating a flaming red psychedelic sailor's delight.

I can't believe how bold I'm getting. After enjoying breakfast in the adjacent dining room, I decided to try to get a picture of the lobby. I put the Populist on the big tripod behind one of the leather couches and explained to the gentleman at the desk what it was. He said he'd watch out that no one bumped it. I went back to the room, finished packing, hauled our stuff out to the car and after exchanging pleasantries about our plans, closed the shutter just as we left. This should help you understand my reference to the Overlook Hotel in a previous post .

Warren Dunes is just a few miles from the Inn. It was still fairly early with the sun low behind the dunes.

We climbed one of the lower dunes. A favorite activity as a child was to climb the steepest face of Tower Hill, the highest one, and run down with our arms windmilling to keep our balance until we fell and rolled down in the sand. A group of 10 year olds demonstrated this while we were there.

Down near the lake this one giant clings to the sand.  The wide angle makes it look a little more isolated than it really is.

It's been there a while from the look of it's gnarly roots. Think I played on it as a child?

It was a brisk October day and there were more people around than I expected. Still, the nearly empty beach and overexposed Portra 400 give it the look of an Antonioni film.

A sailboat passed by just off shore.

I have to conclude with a tribute to our noble steed - union made in Michigan.  It brought us through nightmare congestion on the Boston Beltway in rush hour (starting in Albany!), New York City crossing the George Washington Bridge and downtown Chicago over the Calumet Skyway. We went into the middle of Cleveland, Rochester, Philadelphia and Pittsburgh. We went over the Appalachians in continuous drenching rain. It did everything it was asked including escaping from a few tailgaters in almost 90mph traffic. Also seered in memory is the high fidelity voice of Siri over the car audio system, with her omniscient and insistent description of where to go.

There's always the sweet conflict of having a few frames left in the camera. We returned on Sunday night and Camera Casino's weekly trip to the lab happens at 10:00 am on Monday.

On the way downtown, I took a photo of the Oshkosh Publish Museum to make up for leaving and dallying with other museums.

And then to Miller's Bay and Lake Winnebago to make up for flirting with two great lakes and Cape Cod Bay.

Next, random thoughts on traveling with a pinhole camera.