Archive | May 2023

Lytro Illum vs Light L16: Computationism

Computational photography

The term “computational photography” sounds fancy, but it is a fairly tame concept: using a computer to substitute something that is missing from a conventional optical treatment. Little bits and pieces of computational photography exist in the panoramic feature of your digital camera, any type of in-camera HDR, in-camera tilt-shift (“toy” or “perspective correction” features), and even the Portrait mode on your iPhone. More extensive computational photography is illusive; there are only two cameras that could actually do it. One, the Light L16, was the subject of a previous article. The other is the Lytro. Neither is still made.

The Lytro Illum (“Il-lume”)

With all the hates going around these days, we will focus on something political and judgmental nonetheless: the light field camera, here, the Lytro Illum (pronounced illume, not Ilium like in a Kurt Vonnegut novel). I’ve read now almost every review of the Lytro products, and it seems that people universally get super judgy on this thing. To be fair, it is a weird device – and the tech behind it is probably unfathomable to most people who use it. It’s more like a strange alien technology.

If you have to imagine the form factor, imagine a Sony a6000 that grew up to be really, really big. To put the Illum in relatable terms, the lens is as big as a 500mm mirror lens, is about as light, and it feels like someone has attached an iPhone X to the back. Maybe it’s like a Hasselblad X1 lookalike.

The Illum has some shortcomings and unforced errors in handling that no doubt affected its popularity

  • The lack of an EVF can make it challenging to use in the type of light at which the sensor excels – bright. Eye-level would have been far better.
  • The flash shoe is set forward to maintain the center of gravity when shooting with the extremely rare dedicated flash for this unit. Unfortunately, it does not have the position or spring-loaded security that would make it easy to use with an optical accessory viewfinder.
  • The “focus” and zoom rings are by wire and have the lackluster, disconnected feel of the hydraulic steering on a 1981 Cadillac Brougham.
  • The battery is a complete oddball trapezoid. Because f*ck you. We’re Tech Bros.®

But when actually using the camera, you realize that it probably evoked a visceral negative reaction from reviewers because in many cases, you feel like Luke Skywalker shooting with the blast visor down. You might shoot this without really looking, and fixating on “AF” might slow you down – or actually degrade the results. This is largely a shoot-first and finalize-later type of camera, which is something that makes film people go crazy. It actually made a lot of digital people go crazy too — because although the camera could show you previews, the big stuff is for desktop software.

The limits of plenoptia. The Illum is a plenoptic camera – meaning that it uses an array of microlenses to capture both luminance and directional information about light. Cameras like this capture a phenomenal amount of data and can basically reconstruct a point of view from it.

The shortcoming of plenoptic cameras is directly related to the advantage. For a sensor of a given size, you lose quite a bit of spatial resolution (megapixels) by recording all of that directional information. That means that the Illum starts with a 1″ sensor with a big pixel count (40mp) but computes it down to 2540×1634 (4Mp) at any given distance. This was seen as absurdly low resolution when this camera came out, but given what most people do with photography today, it’s in the ballpark (and Adobe Super Resolution can increase the apparent resolution).

Below you can see how the system can change the focus, the depth of field, and even to a degree, the perspective.

Enhance 224 to 176. Enhance, stop. Move in, stop. Pull out, track right, stop. Center in, pull back. Stop. Track 45 right. Stop. Center and stop. Enhance 34 to 36. Pan right and pull back. Stop. Enhance 34 to 46. Pull back. Wait a minute, go right, stop. Enhance 57 to 19. Track 45 left. Stop. Enhance 15 to 23. Give me a hard copy right there.

Now for some real fun, the Lytro desktop software can output left-right stereo cards or red-blue anaglyphs from a single exposure.

Optics. The Illum lens is interesting – it’s a 30-250mm equivalent with power zoom and a fixed f/2 aperture. Contrary to what you might believe, it does not do all focusing with computational power. The lens essentially operates in four ways:

  • No focusing – works better at middle to long distances. Focus later.
  • Autofocus or manual focus – lock in at a certain point, which improves optical quality around that point but still allows plenty of margin.
  • Hyperfocal focusing – you can enable this on the menu, and the lens will focus to a point that maximizes depth of field/focusability.
  • Infinity focusing – when you need to make sure the distant future is perfectly sharp.

The good and the bad. The Illum has some very positive features:

  • Sharp pictures of things at reasonable distances
  • Focusing pretty much as close as the surface of the lens
  • Arbitrary focusing after the fact (and enough onboard imaging horsepower to preview it on the camera)
  • A really intuitive touchscreen system where to see past pictures, you just swipe right
  • Plenty of depth mapping information
  • Decent ergonomics
  • Good battery life and the ability to charge off USB 3.0 (the Micro B, i.e., flat figure-8)
  • Reasonable hard buttons for AE, AF, and hyperfocal
  • Control wheels front and back
  • A 72mm filter thread
  • Light weight
  • Flash system actually works. It is a Viltrox JY68DL, it’s TTL (somehow), and how exactly it works for exposure is unclear. It appears to be a scene-averaging system.

The software, for its part, has a lot of interesting capabilities beside the usual Lightroom develop-style basics. These include:

  • The ability to simulate apertures from f/1 (shallower DOF than the lens) to f/22
  • Moving the focus point
  • Applying “tilt” (miniature effects)
  • Generating lenticular files, stereo pairs, and red-cyan anaglyphs from single frames
  • Exporting depth maps
  • Changing the perspective of pictures after the fact
  • Generating animations
  • Compatibility at least to MacOS 10.14 and Windows 11 (yes, the software runs in a VM, too)

And the not super good:

  • Due to the very short effective base length, you will really want something within a meter or two of the camera if you are shooting for 3D output. Generally, with 3D, your base length should bear a relationship to distance of the closest subject in frame.
  • It’s difficult to tell whether this camera has a low-pass filter, or whether the algorithms break down at long distance, but distant details can be underwhelming. This is also affected by focus. But the point of a camera with adjustable focus is not really to shoot things where the major interest is at infinity.
  • 2D resolution is not huge. This is not a big deal with Adobe magic, provided that your key details are not too small (e.g. limestone texture on distant building). For anaglyph 3D, absolute resolution in the file is a lot less critical. Resolution is also not a big deal for most internet-related uses.
  • The camera’s zoom and focus rings’ functions can be switched, but their direction cannot be reversed.
  • Not easy to use the massive 4″ LCD in bright sun. Bring your Zacuto finder.

Conclusion: why did it fail?

I would joke that like Tinkerbell, it needed people to believe in it. And they ultimately did: computational photography (in a relatively “lite” form) lives on in cell phones (Portrait on an iPhone, for example, is a limited version of the Lytro focus manipulation that makes a depth map from two very conventional Bayer-array cameras).

In a way, it did succeed. A 4mp final end image is sufficient for almost any modern (read: screen-based) use, but to get there, you sacrifice dozens of megapixels of information that is used only to tell light direction before you output a file.

This concept would have revolutionized photography but for one thing: it was never going to be scalable. Sensors in the 1″ form factor maxed at 40 megapixels 10 years ago, and so to get higher 2D resolution would have required (and still requires) a base sensor that does not exist yet. And although there are 100mp+ sensors now, that doesn’t really translate into a lot more resolution post computation – and those sensors that would never fit in a camera this small (or large…). It seems that you have to have a super-telecentric wide-angle lens for this type of photography, and since you are constrained at a single physical aperture, you want it to be big. If this were built around a 36×24 sensor, it would probably be the size of an M1 tank barrel.

Buying used cameras

This picture taken with a film camera 20 years ago, when this was still a lens worth buying.

It is just as easy to fall in love with a good camera as a bad one

This is the first in what might be a series of articles on how to actually evaluate used cameras. This covers some general principles common to most 35mm and medium-format cameras. Film-testing cameras is stultifying, expensive, and time-consuming. Unless you really have a chance to develop test negatives immediately, you will miss the return period for the camera. So to be practical, let’s at least take some steps to rule out cameras that have obvious problems.

How to check a camera

The following checklists will help illustrate important points to consider and their relative importance. If you are looking at a collectible item, though, all bets may be off.

ConsiderationWhat to checkWhat it means
Body integrity (plastic)Cracks in camera bodies can cause issues with light-tightness, and in extreme cases, with structural integrity. Note that most higher-end cameras in the 1980s and on had plastic covers that look like metal, usually on a metal chassis.Cracked plastic generally cannot be repaired. As long as the camera is light-tight, you should be ok. And in most instances, plastic covers are not used as light seals.
Body integrity (metal)Bent metal covers, traumaIn general, the only metal trauma that matters is the one that causes misalignment of the lens and film plane. Pretty much anything else is cosmetic.
Missing controlsMissing button and knobs can introduce functional challenges. It’s pretty normal for covers like the ones on hot shoes, viewfinders, and flash synch outlets to have been lost over the years.If a non-critical button or switch is missing, you may or may not be able to live with that. Be aware that some missing parts are part of weatherproofing.
Body coatingsRubberized coatings can get nasty. Who thought this was a good idea?The selection of these materials in the 1990s is befuddling, but many times simply rubbing sticky coatings off with a cloth and alcohol can be a solution. Just be careful of any painted-on markings.
Light sealsIf these gaskets around the inside of the back door and around the film reminder window are in bad shape, you will get light leaks.Replacing light seals is labor intensive and within the capabilities of moderately skilled people. The materials are cheap. I would just tape over the film reminder window.
Film railsInside the back of the camera, there are (usually metal) rails. Check to make sure these are not scratched.For reasons known only to Nikon and the Almighty, paint often transfers from the camera pressure plate to the rails and manifests as a black spot or two. Not harmful.
ViewfinderIn general, viewfinders do not affect pictures, although haze, fungus, and misaligned viewfinder elements can make shooting less fun. LED/LCD elements should work; LCD displays should not be bleeding.Be ready to live with the state of the viewfinder; very few cameras have viewfinders that are simple enough for a user to clean safely, especially where exposed beamsplitter mirrors are present.
SLR MirrorSLR mirrors should flip back down after shooting a picture. Some very old SLRs like Exaktas – and some medium-format cameras may require the film to be wound to return the mirror.Stuck mirrors are usually caused by bad light foam around the focusing screen. On some motorized SLRs, a stuck mirror may be symptomatic of a burned-out motor.
Light meterWith batteries (if needed), the light meter should respond to various light levels. With the shutter speed set to the reciprocal of the ISO (for example, 1/125 for 100 ISO), you should get a reading of f/11 or f/16 in bright light outdoors.Meters have some adjustability, but many older types of photocells decay over time. Sometimes you can compensate by changing the ISO setting to fool the meter. If it’s a fully mechanical camera, you can of course use an external meter.
ShutterShutter should fire on all manual speeds. Blades should be free of oil or rust. At the synch speed (or 1/60), you should be able to make out the entire scene looking through the back of the camera and pressing the button.Shutter repairs are best done by professionals; amateur repairs generally do not stay fixed. A non-functioning shutter should be considered a show-stopper.
Iris ActuatorOn an SLR, the actuator is what pushes the iris closed to the selected aperture. If you change the aperture on an SLR lens and shoot, you should see the iris stopping down to sizes that correspond to aperture numbers.Generally, if this is not working, it is due to mechanical faults deep within the camera. If this is not working, then it’s game over.
Film driveThe camera’s film drive should work when you operate the winding lever (or if motorized, should operate when you press the shutter release). Rewind crank (if so equipped) should turn smoothly.Film drive issues are generally beyond reasonable repair.

How to check a lens

ConsiderationWhat to checkWhat it means
ClarityGlass should be reasonably clean and clear (see next section)On all but the simplest lenses, cleaning glass may require expensive professional help. Some things cannot be fixed. The effects of some things are exaggerated.
Iris/ApertureThe iris should be free of oil. All blades should be present. On an SLR, the iris should snap open and closed freely.Iris repairs are generally simple in themselves but require inordinate effort to reach the relevant assembly in the lens.
FocusingFocusing action should be reasonably smooth and not too stiff. Focusing ring should not feel loose. Rubber grip rings should stay on.Focusing rings can be re-lubricated; however, there is a danger that the helicoid will not be reassembled correctly. Many focusing mechanisms use multiple points where the thread could start. Rubber grip rings can be fixed in a lot of instances with rubber cement.
Infinity focusGenerally, when the lens is on ∞, the focusing aid in the viewfinder should line up on a super-distant object.This is mainly true for prime lenses; zooms almost never focus at a hard infinity stop. If you reach focus on an “infinite” object a little before the lens scale reads ∞, especially on a zoom, you should be ok. On rangefinder cameras, you might not be ok. Do note that on SLRs, the “misalignment” at infinity may be your camera’s mirror bumper.
Filter ringFilter rings should be round and able to accept filters of the stated size.Minor bends in filter rings are not a big problem and happen to a lot of people. You can tell there is a very subtle bend sometimes because the filter threads will have a bare-metal, “worn” spot. But the bottom line is that if it accepts a B+W filter, it is not significant. Hoya and Kenko filters have looser threads and will fit rings that are slightly more “out of true.”
Inscriptions/EngravingsShould be legibleThese are purely cosmetic.

What is “good” glass?

The most agonizing part of buying used lenses is figuring out if the glass is “good.”

Clarity. A lens is generally clear enough when you open the iris, look through the back. point it at a halogen light bulb, and don’t see an obvious defect. LEDs are not a good test because no lens passes them. Every lens has a dispersion of 1-10% per internal surface, and LEDs make even new, high-end lenses look nasty 100% of the time. A few dust specks are normal. Even new lenses have them. A film of dust may call for cleaning.

Scratches. In general, scratches are not good on lenses. A couple of barely-visible marks in the coating on the front or rear of a lens is nothing to worry a lot about. A nest of fine scratches is. Cleaning marks are scratches. That seems like a euphemism, but they are unintentional and generally not in the same class as a scratch that can catch your fingernail. A couple of fine marks inside really expensive lenses is usually an artifact of manufacturing (hand-grinding). Recoating a lens only works for the most minor marks, and there are few people in the world who do it. It is also beyond justification cost-wise for any lens that costs less than a thousand dollars.

Haze. This is tricky. Twenty years ago, I would have said that haze is not a big deal. But as lubricants in old lenses break down, or as rare-earth metals corrode, it can be permanent. Do not assume that merely because it’s haze and not fungus that it can be fixed. Sometimes you run into mechanical problems – like the fact that hazed elements are milled into a metal barrel that does not simply come open. The same sealed-in haze thing can happen to viewfinders as well.

Fungus. A surprising amount of fungus comes clean – but you won’t know until you’ve tried it, which often takes an inordinate amount of lens disassembly (fungus usually strikes the middle of the lens, near the aperture, since that is a usual entry point for humidity). A lot of lenses coming out of Japan in the 2020s have really bad fungus. If fungus is minor, and you can live with it, great. If an element is overgrown, repair costs may be impractical. Fungus looks like cotton threads or sometimes little stars. It usually grows from edge to center.

Separation. This is a really ugly thing. It turns out that a lot of old lenses had elements cemented with nothing more than Canada Balsam, which is clarified tree sap. If you see discolored areas at the periphery of lenses, the lens is a goner unless you want to spend megabucks having the elements cleaned and recemented.

Schneideritis. Named for the fabled optical producer of Bad-Kreuznach, Germany, this is a condition where the blacking paint on the edges of a lens element craze, making it look like the lens is full of little stars. Minolta brought this to a high art with the CLE-era 28mm lens. This is correctable as long as the lens cell can be disassembled, but it has a nasty habit of showing up where a cell is milled shut.

Bubbles. Bubbles are completely normal on older lenses. According to myth, it was a sign of quality.

Pits. Sometimes you get pits and pops on front elements. These do not actually require abuse; in some cases, they are the product of pinholes (that were always in lens coatings) allowing tiny amounts of moisture to reach rare-earth metals in glass which oxidize and pop. Although these are intellectually challenging, they are in almost all cases harmless.