This document should be cited using something like the bibtex entry:
@techreport{KAMF,
author={Henry Gordon Dietz},
title={What is KAMF?},
month={August},
year={2024},
institution={University of Kentucky},
howpublished={Aggregate.Org online technical report},
URL={http://aggregate.org/DIT/KAMF/}
}
Latest revision is December 9, 2024.
KAMF might be the world's cheapest consumer-level self-contained mirrorless interchangeable lens camera -- because it's a simple DIY modification of a camera designed for kids. It is also one of the smallest and lightest, although some configurations of the Yashica/I'm Back Micro Mirrorless are slightly smaller and lighter. In any case, KAMF is definitely one of the cutest. "Kamf" is also the Yiddish word for "struggle," and there are several aspects of KAMF for which the word "struggle" applies.
More precisely, KAMF refers to either of two fundamentally different families of camera configurations that we have created:
KAMF isn't a commercial product. It's an easy modification of any of a large family of cheap kid-oriented cameras. These cameras do not offer a lot of photographic control, nor is the image quality very good, but they are fundamentally good designs well implemented, with the result that they are surprisingly functional and even fun to use. All of them that I have played with were obtained via Amazon Vine. In alphabetical order by brand name, here are the links to my Vine reviews of the various branded versions along with a minimal description:
These cameras are all sold as appropriate for 3-12 year-old kids, and that's clearly the intended market. Pricing ranges from about $8 to $30, depending on what extras are included. Some come with TF cards of either 32GB or 64GB capacity, and might include a USB card reader. Many come with some type of colorful soft half-case with a dinosaur or some other character pattern. All have a strap and a USB cable for charging the built-in battery. Here are several versions in their original packaging:
The half-cases vary a lot and the camera body shape differs very slightly in allowing for either USB C or USB micro, but the body housings are otherwise identical and interchangeable across brands. The camera body housings do come in several different colors, and also differ in that some have a matte vs. glossy finish. In common to all are the following features:
Internally, the cameras continue to be very similar, but there are at least two major chipset variants that use different processors and the firmware menus also vary a little. The USB C version seems to be a newer "upgrade" of the USB micro version, but the differences are not qualitatively significant. For our purposes, it doesn't make a huge difference which version we start with. It is also worth noting that the character case will not fit on most KAMF, although it can be used with the C-mount micro format version. Thus, our starting point is a camera that looks like:
Yes, that is a quarter as a size reference. The children's camera is 83.5mm wide, 62mm tall, and 48.5mm thick, with a weight of 59.3g. That's really quite small and very lightweight. The camera first marketed as the smallest interchangeable-lens mirrorless, the Pentax Q, is 98x57x31mm and approximately 200g. Slated to start shipping in November 2024, the Yashica/I'm Back Micro Mirrorless is claiming that it will be the smallest mirrorless at 77x50mm.
If you're an experienced DIYer, there's not a lot I need to say, but building KAMF is not a project that requires lots of DIY experience. Here's what you'll need:
You may have noticed that I didn't include any prying tools, soldering, nor even programming support: none of those things are needed. Everything pretty much screws together, with just a few points that might be tacked with glue.
So, to get started, remove the four screws you see on the back of the camera. The front and back separate as soon as you remove thiose screws... well, except on some versions there is a little round sticker on the camera bottom that you'll tear when you separate the halves (presumably a sticker to detect when you have voided your warranty). What you see should look like this:
Now you can see the battery mounted on the front of the main circuit board, with some wires connecting things. The long ribbon cable is connecting the front-facing camera module, and in some versions this cable is glue-tacked to the back of the black oval microphone module (as it is here). You'll also see that the camera module's metal backplate is tack-glued into a black holder, which in turn is screwed into the front white lens barrel. Let's remove the white lens barrel next:
The square black camera mount with screw holes on left and right wings is now free, and we can use that as a mounting jig in KAMF. On the front of that jig is fitted a clear plastic filter in a cylindrical holder; that holder and glass should come free as soon as you have removed the white lens barrel, and you don't need those parts. If you use your screwdriver to push a bit at the dot of glue on the metal backplate of the camera module, the glue will pop off and you can free the camera module from the holder by essentially unclipping it:
This makes it pretty obvious that we are looking at a fairly generic 1/6" camera module with a tiny screw-in lens (with built-in NIR-blocking filter. That tiny lens screws in, although there might be a drop of glue on it to hold the focus setting. You'll need to unscrew the lens -- fully remove the lens for the micro KAMF, but only unscrew it a little for the medium-format KAMF. Basically, partially unscrewing this lens allows you to adjust the camera's focus to focus on the DCO's 44x33mm screen, which we'll talk about more in the medium-format KAMF section of the document. What does the actual camera chip look like?
Here, you can see the sensor area on the chip. To make it easier to see, we have also removed the front of the camera. That required breaking the glue tack that held the ribbon cable to the microphone oval and removing the oval from the front (it is held by stickly material on the front edge of the oval and can eaily be removed and replaced). The camera as shown here is broken-down more than you need to do to make any version of KAMF -- that wasn't so bad, was it?
If you removed the camera module as described above, you can easily clip it back into its holder when you are done. Assembling any of the KAMF versions basically reverses the disassembly process, with the subtle difference that the white lens barrel is replaced by a 3D-printed part -- which even gets attached using the same screws and screwholes.
Who should build Kentucky's Adorable Micro Format camera? Well, if you just want a cute little camera, honestly, these children's cameras are pretty cool right out of the box. However, a little modding can get you some pretty interesting variants. Here's an unmodified green one alongside a blue KAMF visible-only using C-mount and a purple KAMF full-spectrum using Sony E/FE mount:
Here they are again, in a different order with some lenses attached:
The lenses here are a native FE-mount PerGear 35mm f/1.4 and a C-mount Tokina 6-15mm f/1.4 zoom. However, these tiny mirrorless cameras can use just about any manual-focus lens that can be adapted to C or E/FE mount. For example, here they are again but with an old Minolta MD 50mm f/1.7 adapted using a standard $10 MD-to-FE adapter.
So, how do adapted lenses perform on KAMF micro format? The answer depends mostly on some attributes of the sensor. The sensor is approximately 1/6", which means that the image area is about 2.4x1.8mm with a diagonal of 3mm. The cameras return images with as many as 48M pixels, which would suggest really tiny pixels needing an amazingly sharp lens -- but sensor resolution seems to be just 640x480 pixels, in which case a pixel is roughly 3.7um.
Given that sensor, what do the lenses behave like? A "full-frame" camera has a 135-film-sized frame of about 36x24mm, giving a diagonal of approximately 43.3mm. Thus, the crop factor for this KAMF is approximately 14.4x. The result is that a 35mm lens on KAMF behaves like a 500mm lens on a full-frame camera, and 50mm behaves like 700mm. The PerGear and Minolta lenses shown above thus give the reach of quite extreme telephotos, while still providing the light-gathering ability of their f/1.4 and f/1.7 apertures. The 6-15mm Tokina zoom effectively becomes something like 85-210mm f/1.4. In sum, great news for telephoto shooting, but problematic for getting wide angles...
How sharp are these lenses in such a tight crop? Well, here's where the low pixel count of the sensor helps. It turns out that the pixel pitch is almost identical to that of my Sony A7RV full-frame mirrorless. In other words, these are not tiny pixels and good lenses can actually project decent levels of detail on them. We also are helped a bit by the fact that we are only using the central region of the projected image, which is usually better corrected than farther off axis. Still, it is worth noting that many C-mount lenses do not resolve particularly well because they were designed for low-resolution sensors or film; thus, some need to be stopped down a little to be acceptably sharp. That is unfortunately true of the Tokina zoom shown...
One of the nice features of KAMF micro format is that it easily can be a full-spectrum camera, recording both visible and NIR (near infrared) light. This also implies that it can easily be filtered to record any subset of that spectral range.
Most camera sensors are inherently comparably sensitive to NIR and visible light, with a usable range of about 400-1100nm. The problem is that wavelengths much longer than about 700nm are barely seen by humans, so light in the 700-1100nm range is typically considered to be NIR contamination altering the colors recorded so that they do not match the colors we saw. The dyes used in cameras to distinguish blue, green, and red color channels also pass somewhat different amounts of NIR, with green leaking less than red and blue, so NIR light commonly adds a magenta tint to the visible-light image. To avoid this, most cameras incorporate an NIR-blocking filter in their sensor stack, and it isn't particularly simple to remove that filter. Companies like MaxMax will modify a camera for you, but it isn't cheap. However, these children's cameras don't place the NIR-blocking filter on the sensor, but instead within the lens. Thus, when we remove the original lens to make KAMF micro format, we also make the camera full-spectrum sensitive. This makes for several options:
The spectral flexibility of KAMF is one of the more compelling reasons to build and use it. The small sensor size tends to help here in that things like NIR "central hotspot" problems with lenses are not obvious if your entire sensor is within the hotspot (Kolari has an interesting discussion of these phenomena). Additionally, many applications that call for specific spectral sensitivities do not require high resolution.
If you've decided that you want to build a KAMF micro format camera, the key question is with what mount? No matter which mount you pick, all have in common:
Here's the C-mount version on a mini-tripod and on a webcam stand:
The currently available mounts follow.
C-mount is a 1 inch diameter, 32 threads-per-inch, screw-thread mount with a nominal flange distance of 17.526mm. It is probably the most natural choice for KAMF in that a wide variety of suitable inexpensive and small lenses are available in this mount. Many of these lenses were designed either for small-format movie film or NTSC video cameras, so the downside is that resolution of many of these lenses wide open is unimpressive. The nicest aspect is that C-mount KAMF is quite small and lightweight:
The plain file is kamf240622_cplain.stl. The two-color version combines kamf240622_c.stl and kamf240622_ctext.stl. Flip the STL for FDM printing. In these versions, the camera module is mounted directly. Optionally, you can set an 8x8mm filter in the boxed shelf in front of the camera module; place a drop of glue on the edge on the shelf and place the filter from the front of the mount. Here are a couple of shots taken using KAMF with the C-mount Tokina 6-15mm f/1.4 zoom:
Those are 48MP JPEGs from KAMF, but remember that the sensor really only has 640x480 pixels...
Sony's E-mount seems huge for such a small sensor, but it has a short 18mm flange distance and Sony has led the mirrorless camera market for some time, resulting in more lenses and adapters being available for use on E-mount than for any other mount. Sony's compatible full-frame variant, FE-mount, essentially created the full-frame mirrorless market and thus added even more lens choices. The flange is even short and wide enough so that C-mount lenses can be adapted. The plain file is kamf240622_eplain.stl. The two-color version combines kamf240622_e.stl and kamf240622_etext.stl. Flip the STL for FDM printing. In these versions, the camera module is mounted directly. Optionally, you can set an 8x8mm filter in the boxed shelf in front of the camera module; place a drop of glue on the edge on the shelf and place the filter from the front of the mount. Note that this design has a larger area around the tripod mount, thus providing an opportunity to reinforce the thread.
Who should build Kentucky's Approximation to Medium Format camera? At some level, I feel compelled to answer "nobody." It is a much more special-purpose tool than the KAMF micro format versions, mostly useful where you want to give an "old timey" look to images and don't need high resolution.
Before getting into the construction and use details, let's get one thing straight: the KAMF sensor is tiny, not 44x33mm. This KAMF is a DCO, a digital camera obscura. Some properties of a medium-format camera come from having a truly huge sensor area, and KAMF will not duplicate those aspects. For example, a larger sensor can have better low-light performance, lower noise, and higher resolution -- KAMF will not deliver those benefits. In fact, the light sensitivity is actually poorer than when using the children's camera in its original configuration. However, the benefits that come from having the lens project a larger image can be obtained simply by having KAMF's tiny sensor photograph an image projected onto a 44x33mm screen. Thus, KAMF will capture the shallower depth of field and wider view angle of a medium-format camera. Put simply, the images will have the "feel" of medium-format, but technical image quality will be slightly poorer than the unmodified children's camera delivers.
Compared to KAMF micro format, the medium format versions are fairly large because they need to have two lenses. The first lens in the one that is native to the children's camera and focuses it on the screen -- requiring some distance between the camera module and the screen. The second lens is the adapted that projects an image onto the 44x33mm screen -- and it has to sit some distance in front of the screen to make that work. It would be possible to print a single part that contains mounts for both lenses and the screen between them, but instead we have standardized on two parts:
The screw-thread coupling between the two pieces is an oversize thread with an easy-to-print 45-degree thread angle. The result is a connection between the two parts that is both wiggle-free and strong. It also means that only the second part needs to be changed to change the adapted lens mount for KAMF medium format.
As described above, the first part mounts the native lens and the screen it is (macro) focused on. In some sense, it makes the children's camera into a stand-alone copy camera, designed only to photograph the backlit image placed on the 44x33mm screen plate.
The 3D-printable design for this part is kamf240625_4433.stl and kamf240625_4433txt.stl. The STLs should be flipped for support-free printing on an FDM printer.
To avoid fogging images captured, we recommend printing the base part in an opaque black material and use of a contrasting color for the text. The catch is, the image projected on the screen and photographed from the other side is often much dimmer than the light outside this part, so even slight translucence in this part can cause problems. Be warned that, due to use of organic dye, even black filament is often not entirely opaque in the NIR, and no NIR-blocking filter is perfect: even invisible-to-humans NIR translucence can cause fogging. If there is any hint of translucence, we strongly recommend using black paint on the inside to prevent light leaking through this part. Also note that translucence is not the same as transparency; translucent materials can even act as light pipes to transmit some light around corners, etc.
Once this part has been printed, it is attached to the camera body using the same screws and screw holes that originally attached the white lens barrel.
The camera module including its native lens is not directly mounted in this part, but is first clipped into the black plastic holder and then that is fitted into this part. The catch is that the native lens will need to be refocused a little (to a mild macro range) in order to focus sharply on the screen. This can be done by turning the native lens a small amount within the camera module before installing it. I recommend itteratively adjusting the focus and holding the camera module the correct distance away from a target to check focus using the live view. Keep in mind that the live view screen is of lower resolution than the sensor, so the live view image might look sharp when the focus is slightly off; you are looking for the middle of the focus range in which the live view appears sharp.
The focus thread of the native lens has enough friction so that it doesn't need glue to hold position, but you will want to use a drop or two of glue to lock the camera module holder into the printed part with perfect alignment. In fact, this second alignment tweak is even more touchy. Watch the live view while installing the holder to confirm that you don't see a crooked edge of the 44x33mm screen. We are talking about tiny fractions of a mm making a visible difference in alignment with the screen. Also note that each lens inverts its image, so the camera module needs to go in upside down to make the image appear correct in the live view. This means that the flex cable to the camera module may need to be folded or twisted a bit, but there is plenty of space in the camera to allow doing that.
Once the above has been done, close-up the two halves of the camera body. Here's what it should like... although weight of yours will depend on slicing parameters, choice of filament, etc.:
The last step in building the first part is installing the screen. The screen should end up looking something like this:
However, there are various trade-offs in choice of screen material. I've discussed these issues in depth before, so here I'll simply say we want a material that is diffuse enough to give a true image without a central hotspot, but the more diffuse it is, the dimmer and less sharp the image tends to be. With only 640x480 pixels, one would think that KAMF can afford to favor a more diffuse screen, but that also limits the feasible scene brightness range to scenes that are outdoors or very well lit. The one shown here is cut from HP C3885A high-gloss white film (a plastic inkjet paper), but the Roscolux sampler book (mentioned earlier for color filters) is a great source for diffuser material. Vellum paper also can work quite well, although it might have more of a texture. Simply cut a piece somewhat larger than 44x33mm and tape or glue it to the mask edges on the front of this part making sure not to intrude on the screw thread.
Unlike KAMF micro format, it is quite easy to change the adapted lens mount on KAMF medium format -- so you might want to print more than one. The second part simply screws into the first without needing to disassemble anything else.
The interesting side issue here is that the best choice of mount probably isn't a mount normally used for cameras with 44x33mm sensors. The dominant medium format mirrorless mounts are Fuji's G mount (used on their GFX cameras) and Hasselblad's XCD mount, but there are not a lot of lenses made for those mounts and none of them are cost effective for KAMF. All we need is a lens that can cover 44x33mm (55mm diagonal) with a reasonably even 640x480 resolution, and lots of cheap and readily available lenses made for 135 film (full frame) cameras can do that. I have a partial list of measured coverages posted at DPReview. Various full frame mirrorless mounts are better than medium format mounts at adapting such lenses...
As for KAMF micro format, the short 18mm flange distance and huge number of lenses native or adaptable to Sony's FE-mount makes it an outstanding choice here.
The file containing the 3D model is chem230107emount.stl. You may have noticed that isn't named for KAMF; that's because this E-mount part is actually in common with the CHEM DCO that I described in Digital camera obscuras, published in Electronic Imaging in January 2023. Here's what the FE-mount version looks like next to an actual full-frame-sensor Sony mirrorless:
KAMF is not really that much smaller the the Sony A7RII shown in some ways, but it is much lighter and behaves like it has a 44x33mm sensor. I don't have a 44x33mm sensor camera to sit KAMF next to, but CameraSize.com gives us a handy comparison between the A7RII shown above and the 44x33mm-sensor Fuji GFX100II:
KAMF is quite a lot smaller than any GFX camera and about 1/10 as heavy. Of course, the rather significant disadvantage in using KAMF is that it only has about 1/300 the resolution of that GFX100II... Still, KAMF's FE-mount allows it to use many more lenses, and many of those are smaller and cheaper. For example, the native FE-mount PerGear 35mm f/1.4 gives reasonable coverage, and it costs less than $150 and is tiny:
A 44x33mm sensor, or that size screen in a DCO, gives a crop factor of about 0.79x, so this PerGear behaves like a 28mm f/1.4 on KAMF.
This FE-mount design here is very basic, derived from the flange structure used in FE-mount lens caps. It does not incorporate a locking mechanism, nor does it stop the mounted lens at the ideal rotational position. A future version will hopefully resolve both these issues...
The M42 mount is a metric thread with a diameter of 42mm and a 1mm per thread pitch, with a flange distance of 45.46mm. It is a very simple mount to make and provides an exceptionally solid and precise attachment with the main disadvantage being that changing lenses is a bit slow. In the early history of 135 film SLRs, it was used as the native mount by Praktica, Pentax, and Zenit and became commonly known as the "universal screw thread mount" because of how many cameras from different brands could use lenses in this mount either directly or with a simple adapter. That was quite an accomplishment in that even today it is unusual to see multiple camera brands agree on a lens mount. For that reason, many 3rd-party lenses have been built using M42 mount and a wide variety are available as used lenses.
The file containing the 3D model is chem230115m42.stl. You may have noticed that isn't named for KAMF; that's because this M42-mount part is actually in common with the CHEM DCO that I described in Digital camera obscuras, published in Electronic Imaging in January 2023.
This M42 mount does not incorporate a locking mechanism, nor does it need one. Unfortunately, it also does not necessarily stop the mounted lens at the ideal rotational position. It so happens that the M42-mount SMC Takumar 50mm f/1.4, a lens famous for its outstandingly smooth bokeh, ends up in approximately the right orientation and makes a rather nice lens for KAMF:
Here are a couple of 640x480 handheld shots using an M42 Super Takumar 135mm f/2.5 on KAMF:
The screen used adds significant texture and limits sharpness, but suffers very little hotspotting. Despite the low image quality, I think these shots clearly demonstrate the depth of field associated with a 44x33mm capture. Note also that the camera module was not precisely aligned, as we see a bit of the screen edge mask in the lower right corner.
The Nikon Z mount is the full-frame mirrorless mount with the combination of the shortest flange distance (16mm) and the widest throat (55mm -- the same as the diagonal of the 44x33mm format). It hasn't been around as long as Sony's E/FE mount, but in the long run Z should be able to adapt more lenses than E/FE because it can mount a Sony E/FE adapter.
The file containing the 3D model is kamf240627z2.stl. This Z mount does not incorporate a locking mechanism because it is based on a lenscap design, but in practice it is usable a long as you're a bit careful not to dismount the lens while focusing or zooming.
Here I have summarized the development of KAMF and explained how you can build and use one yourself. The real motivation for development of KAMF was to find a way to lower the barrier for people to build their own interesting stand-alone cameras, and KAMF achieves that goal even if the image quality is a bit disappointing: KAMF is very cheap and the DIY skills and effort needed to build it are minimal. Still, we plan to continue to improve the design...
A couple of months before writing this, I posted two surveys on DPReview's Adapted Lens Talk forum to try to discover what the community would really want -- at least in terms of lens mounts:
The community response was underwhelming, but both surveys remain open, and hopefully more community feedback will happen now that the full designs are available for people to build and use.
If you have any comments or suggestions, you can send them to Professor Hank Dietz or, better still, post in the above noted DPReview forum threads.
The only thing set in stone is our name.