Used Camera Database Blog

Yashica-Mats are known for good image quality at a low price, but that does not mean that we can not improve on a good thing.  One of the simplest improvements is to add flocking material inside the main chamber of the camera to reduce internal reflections.  This post details my experience flocking my Yashica-Mat 124 based on information I found in Flickr Yashica TLR discussion groups, specifically Annoying glare in photos from my MAT-124, adding flocking: internal reflections, and Reflections Inside The Film Compartment.

Here is a shot of my film compartment:

The film compartment is painted with matte black paint, but the paint does not absorb all light.  For instance, take a look at the back surface near the lens — see how it reflects the and has a much lighter color than the sides?  Typically, black paint will tend to reflect light more at very large angles (perpendicular to the painted surface) and very shallow angles (glancing angles).  Since any reflected light can bounce and hit the film at a location where it isn’t supposed to be, this can cause strange flares, or bright areas, on the image (see threads above for examples).  Also, all that light bouncing around in the film compartment will decrease image contrast by increasing the general exposure of the film.

Newer cameras use baffles and ridges in the film compartment to reduce these reflections, but older cameras like the Yashica TLR series do not.

In my case, there’s even an area in my film compartment where the paint has worn away (see above). I’m not sure why that is, but I have to assume that it does not help my image quality!

Luckily, it turns out that there are felt-like materials called flocking that absorb light better than the stock paint.  Flocking, by definition, is the application of many tiny black fibers that absorb light very well.  While it is possible to flock by applying glue and shaking on the fibers, you can imagine that the glue and shake process would not be ideal for a precision instrument like a camera.  Luckily for camera hobbyists like us, the home-brew telescope industry creates a market for self-adhesive flocking that is quite inexpensive.

The best source I know of for flocking is from a company called ProtoStar in Ohio.  ProtoStar’s “Flocked Light Trap Material” costs only 50 cents per 30 square inches, includes a nice adhesive backing, and is very easy to use.  If you are a resident of the United States, it is actually slightly less expensive to buy it in roll form instead of the die-cut sheet that they offer on their web-site (by a 30″ x 20″ roll).  Either way, at about $17 including shipping, it is quite a deal, since one sheet will let you do a TON of cameras.

So, I went ahead and ordered a sheet of the material and set out to flock my Yashica-Mat 124.  Here are the details of how I did it and the tricks I learned.  My hope is that others can use these instructions to flock their own cameras.  Honestly, it is an easy process that requires some household tools and a little patience, and it should only take about an hour to do it, maybe less.

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To start out, you’ll want to open up the back of your camera and look around.  The goal is to cover, or flock, any exposed surface that might catch light, but you’ll want to keep the low against the walls of the chamber and out of the direct light path.  Do not worry about cleaning the chamber before you flock because the flocking will cover everything up (unless there is oil or grease build-up that would mess up the adhesive, but if you have oil or grease in your film compartment your camera has more major issues than the flocking can fix!).

Then, gather your materials.  The ones I used are above:

• Camera (every TLR has similar internal dimensions, so this process should work for any of them)
• Roll of flocking material (upper left in the image)
• Scissors
• Tweezers.  Mine were pretty short and fat and didn’t work that well.  Ideally, the longer and thinner the tweezers are, the better!
• Scotch tape (masking tape would work too)
• Blower (or other method to clean the camera lenses)
• Paper (for test-fitting before cutting the flocking to size)

The basic procedure for installing the flocking is pretty simple:

1. Determine the correct size of the flocking.  I started by cutting paper to size after pressing it into the area I wanted to fit, then using that as a template to cut the flocking, adding extra size if in doubt.  Then, I test-fit the flocking and trimmed it to fit exactly where I wanted it.
2. Remove the backing and lick or moisten the adhesive.  Licking the adhesive will reduce the initial adhesion and allow you to adjust or restick it more easily.
3. Place the flocking in the appropriate place with tweezers, tack it down, smooth it out using the tweezers tips.
4. Check the location once it is in place, and if it isn’t right, pull it off and repeat steps 2 and 3 as necessary.

Lens Cylinder. The first location I applied the flocking was in the cylinder by the lens.  This was honestly the hardest part of the whole procedure, since it is a tight fit, deep in the camera, and the adhesive likes to stick before you want it to.  It may help to rack the focus until the cylinder protrudes into the chamber as far as possible.  Also, make sure you leave a gap between the flocking and the edge of the cylinder, since tolerances are tight and if you get too close you’ll block light from reaching the film.

I recommend using two pieces of material since the material can expand/contract slightly with temperature changes and it would be bad to have it bubble up.  It took me a lot of fiddling to get it right, especially since I was positioning a black material in a black area and my hands often got in the way of my light.  What finally worked was to pre-curve the flocking, position it with tweezers, and tack it down with the second probe (a knitting needle in my case).

Front and back of chamber. The next portion I did was the front and back of the main chamber.  I used two strips for both the front and back, but it would probably be possible to do them in a single strip if you were careful.  I started out by rough-cutting a piece of paper and marking the sides by squeezing it into the corners with my fingernails.  Then, I cut it down, test-fitting as I went, until I had a decent template for the flocking.  I ended up trimming the flocking a few times too before I stuck it down.

Oh, and an important note — before applying the front and back flocking make sure you rack the focus so that the lens cylinder projects all the way into the body.  The front/back walls have concave portions that allow the cylinder to move forward and backward during focus.  If you have the focus out and place flocking too far down, you’ll cover up the areas that the cylinder needs to move by, and you could get binding as you focus.  I was lucky and just happened to have the focus in the right place, but I figured I should warn you.

I ended up with a gap between the two strips, but this flocking really does not have to be done perfectly.  Since the goal is to cut down on overall light and reflections, and since the flocking has height to it already, gaps won’t reflect much light at all.  Notice that I left the gap on the portion that curves away from the lighting frustrum — so I doubt any light would even hit it!

During this portion, I pulled off one of the strips to get it positioned better and the flocking separated from it’s backing (the adhesive portion from the fuzzy portion).  So, it is possible to destroy the flocking when you remove it, and you need to be somewhat careful once you stick it down.  On the other hand, you can always just grab a new piece and it will cover over any residue!  Here’s a shot of the separated piece:

The portion on the left is what I am talking about.  The portion on the right is just a piece of paper I stuck the broken flocking to.

Chamber Sides. Once the front and back were done, I did the sides.  At first, these look really nasty because there are all sorts of strange shapes in the sides.  Ultimately, though, that geometry doesn’t need to be preserved and the whole side can be covered with a full piece.  Did I mention that this flocking process does not need to be perfect?  You can see in the image above how I used a single piece to cover the whole side, just covering over the uneven portions.

Also, note that I didn’t bring the flocking all the way up to the film plane on the sides because it would get in the way of the image on the film.  Note how the chamber opens up next to the film.  On the front/back, you can go all the way up because there is a recessed portion, but you can not go all the way up on the sides without reducing the image area.

Lens Wall.  At this point in the process, I had flocked the chamber as shown above, and I thought I was done.  But, looking at it, it seems like the lens wall (the wall that the lens is mounted in) is still pretty reflective if it does not have flocking on it.  I decided to go ahead and put some flocking on each side of it just in case.

My main reasoning for this extra bit of work was that film itself can be reflective, and light that reflects off the film could reflect off this back wall (the back wall is clearly not as dark as the flocked area) and decrease contrast.  I’m not positive it’d even be an issue, but I figured I’d be easy to add some flocking and I might as well be safe.

I ended up cutting some strange looking pieces to fit in there (even using two on one side) but, again, it does not need to be perfect to do a good job.  Just be careful that you keep all flocking away from the lens cylinder because you do not want to get it stuck in the focusing mechanism (lens cylinder).

Cleaning.  At the point, the full chamber was flocked, but the flocking material sheds fibers a reasonable amount and there were tons of them on my lens.  So, I used a blower to clean it off, then some lens tissue.  This image is a bit misleading because I actually blew it out upside down to make sure the fibers didn’t fall back into the camera.

Then, I used scotch tape as a lint remover to get all the little bits of white fuzz off the flocking that had accumulated during installation. It is also good to get off any loose fibers so they don’t fall into the camera. Just roll a little circle, stick it on your finger, and roll it around the flocking. Once it gets dirty roll another piece of tape and continue until everything is nice and lint-free.

Finally, above is the completed flocking.  As you can see, the flocking material reflects significantly less light (in fact, I had to adjust the image in photoshop to get any texture to show up!).  I haven’t yet had a chance to run a roll of film through the camera, but I hope to today.

Overall, the process took me about two hours, but I was also doing a lot of fiddling with my digital camera and flash to document things.

Also, I added up the size of the flocking I used, and it came out to be only 6 inches by 4 inches, or only 24 square inches!  Considering the 30″x20″ piece of flocking I bought, I have a TON left over.

Hopefully this post has encouraged you to flock your Yashica-Mat 124 (or any other TLR — the same process should work on almost any camera that needs flocking).  It really is an easy process.

Feel free to leave a comment if you have any questions or tips!

Just a quick note to let you know that the lens search page has been improved with the ability to sort by any of the criteria on the page in either direction.

I know it doesn’t sound that important, but it makes it handy to be able to sort by specific criteria, such as decreasing prices.

There was also an issue with live eBay searches, but I was able to resolve it this morning.

This will be very brief because I’d like to sleep…

Average prices are back up — although some aspects are protected by a login and historical data does not go quite as far back.

I’ve also made a number of improvements to the splash screens, lens views (Amazon prices for Canon lenses!), and a few other places.  Registered users can take advantage of the Lens Resale Chart again.

Take a look around and let me know what you think!

It has been brought to my attention that I may be in violation of the eBay Developers Program & API License Agreement in the way that I collect historical lens prices from eBay.  So, until I’ve contacted eBay and clarified what I can and can’t do, I’m going to disable display of historical prices on UCDB.  Live auction listings will still be available though.

Apologies for any inconvenience this causes!

Ever wonder which Canon lenses have the best resale values?

Well, wonder no longer with the UCDB Lens Resale Value page.  It is computed automatically from the lens database.

While I was not surprised to see that so many “L” lenses were on the list or the strength of the Tamron 17-50mm f/2.8 , I was a little surprised to see how many EF-S lenses made the list.

Bleary-eyed, but functioning, I’ve just finished a once through of all the lenses in the database.  I made a tool that helps me sort through the previous sales and hopefully that will help me keep prices more accurate.

The majority of the changes were to the back-end and to the FD lenses.  I made the “new FD” (or FDn, or nFD) more restrictive, so in some cases you’ll want to check the FD lens listing even if you want the new-FD mount, mostly because the majority of sellers do not distinguish the lenses in their titles.

Also, lens averages might be a little odd for a couple of weeks while I integrate the historical prices (those past 60 days old) into the system.

Overall though, I think you’ll find the database much improved and less noisy.  In the past couple of weeks I also made some cosmetic changes, and I’ll continue to do them as I have time.  If you have any suggestions for functionality (or anything that just bugs you) leave a comment!  My goal is to make the site as useful as possible for camera enthusiasts!

This afternoon I finished adding the FD series of Canon lenses to the database.  If you are not aware, the FD series was the manual focus 35mm SLR series the predated the current EOS (autofocus) system.  The FD lenses were made from 1971 to the late 80’s and contained two basic mount types (FD and “new FD”, or FDn).  The FD cameras were also backwards compatible with the FL lenses.  The Wikipedia page on the Canon FD mount has a lot of great historical background on the FD series of lenses — for now, I’ll just hit the high points as an introduction to the FD series.

Indexing camera lenses in an organized way is always difficult, and the FD series has lots of quirks.  First, all FD lenses will fit FD mounts, but the FDn mount uses a rotating ring to emulate a bayonet-mount.  To distinguish the mounts in the database, the new FD lenses are marked with the mount ‘FDn’.  Within the specific mounts, there are many variations, especially in lens coatings.  The main coatings are S.C. (Spectra Coating) and S.S.C (Super Spectra Coating).  The new FD lenses, with the exception of the inexpensive 50mm lenses, all use an S.S.C coating but the old FD mount has multiple variations.

Another interesting quirk of the labeling is the ‘L’ series, that designates a lens with asphericaL elements (and other Luxury elements) .  The L-series started in the FD line, but was predated by lenses marked ‘AL’ or ‘Aspherical’.

The FD series also included some experiments in autofocus, including the ‘AC’ series, and one ‘AF’ lens.  All autofocus lenses will operate on an FD mount, although the AC series will not allow autofocus without a camera that supports it.  If you are curious, here is a search for the autofocus FD lenses in the database.

While the FD lenses are added to the database, it will take me a little while to get the quirks out of the searches.  Most eBay sellers do not distinguish between the lens mounts, although it can be relatively easy to distinguish them if a picture of the mount is listed.  As a result, it will take me a while to tweak the search logic to present relevant results, especially since many of the lenses are quite rare.  If you have recommendations, let me know!

For now, you can view the new lenses by using the search.  For instance:

• All lenses that fit FD cameras
• All FD mount lenses (not new FD!)
• All New FD (FDn) lenses

Since the FD line is a completely discontinued line of lenses and cameras (Canon completely revamped the mount for EOS) there is less competition for lenses and there are often many good deals out there.  I’ve been toying with obtaining an FD camera and a few lenses myself for when I want to shoot on 35mm film.

If you’d like more information on the FD line, here are some great resources (many of which I pulled from for the list at UCDB):

• Wikipedia page for the Canon FD mount.  Great overview of the line, it’s quirks, the FD mount cameras, and a complete list of lenses.  I pulled my master-list from here.
• Photography in Malaysia: The Canon FD Resources — The FD Lenses.  Amazing, amazing site with tons of information about all the lenses, including tons of pictures and specs!  A great place to start when looking at FD lenses, but be nice — they have limited bandwidth available.
• FDReview.com.  A new site, with FD camera and lens reviews and information.  I’m excited to see where they go!
• Denis Baron’s Canon FD Lens Info.  Basically a big table of all the FD lens specs.  A useful resource.

As I mentioned earlier, I’ve been having trouble with my light seals on my Yashica-Mat 124.  I tried replacing them with felt, but it did not really fix the problem.  So, I searched around the internet and found everyone talking about John Goodman’s light seal kits (he goes by Interslice on eBay).  Since the seal kits are only $10, I went ahead and got one.

The kit itself is very well thought out and includes everything you see in the picture above.  Of course, John provides many kits for many cameras, all with the pieces you need pre-cut and ready to be applied with the provided instructions.  But, if you look at the contents of the kit, you might feel a bit ripped off.  $10 for a tiny bit of felt, a stick, and some photocopies?

John’s kits are a great deal, but you need to realize what you are paying for.  The deal in the kit is not the raw materials — it is the experience embodied in the instructions and selection of materials. From what I read, John has recently limited the amount of materials he’ll provide because other sellers stole his instructions and started selling competing kits on eBay.  So, the choice to limit the materials in the kit is just a sound business strategy.

John’s instructions are very detailed and clear with a ton of little tips that I never thought of when I used felt.  Obviously, I can’t share all of them with you now because that’d undermine his business, but I will share one that is obvious yet I never thought of it: remove the back door of the Yashicamat 124 before trying to apply the seals!  Of course, John gives great instructions on how to remove the door safely.

With the instructions and the pre-cut seals, the whole process went very smoothly.  John includes a custom-cut bamboo tool that helps, especially with getting the new foam in.  I didn’t find the tool that useful for removing the old goo though.  The foam is top-notch and applies pretty easily if you take your time.

So, if you need to replace your seals, I highly recommend an Interslice kit (click on the link to see all of his listings — he covers a lot of camera models, including Canon AE-1, Mamiya C330, Olympus OM-1, etc).  Remember though, you are paying for the experience and information, not necessarily the materials.  And $10 is a worthy investment in the information he provides!

* * * * *

FYI, the new seals did not fix my light leaks.  This is no fault of the kit — I believe my Yashicamat back is bent and that is causing the leak.  My current solution is to cover that side of the back with gaffer’s tape when I’m shooting with it, but more about that another time.

In The Scanning Problem Revisited, I outlined the basic construction of a do-it-yourself scanning project that would allow me to digitize my 35mm and medium format negatives.  This post describes the polished version of the idea: a combination light table / transparency scanning apparatus that gets my film photography into the computer for minimal cost.

Honestly, this project is really only applicable if you are incredibly strapped for cash.  A more permanent solution (and better quality) is to just buy a medium range flatbed scanner with a transparency attachment.  For instance, the Canon CanoScan 8800F, Epson Perfection V500, and HP Scanjet G4050 are all very capable film scanners for under $200 (my preference would be the Epson, FYI).  Granted, they are not suitable for scanning something you want to post in an exhibition, but for basic film scanning and printing at 8×10 or smaller, they are perfect.

And that is my goal for this project; to put off the purchase of a scanner for a little longer with minimal investment.  My basic requirements are to allow me to print shots at up to 8×10 resolution (approx 8MP), handling 35mm, medium format, and contact sheets.

The end result is simply a light table augmented with flash.  The light table lets me examine the negatives, and when I want to digitize something, I can just take a picture with my camera.  I’m quite happy with the end result and image quality!

Basic Construction:

The image above shows the basic idea of the project (as with all images, click to see it larger).  Materials are minimal if you already have a decent digital camera with an off-camera flash setup (Strobist is a great resource for that kind of stuff).  Of course, if you don’t have a camera and flash, it would be much cheaper to buy the camera!

Materials and Tools:

• Digital camera
• Macro lens
• Flash with off camera trigger (wireless is very useful)
• Sturdy cardboard box
• Plexiglass (I got an 8×10 sheet at my local hardware store for $2.75)
• Fluorescent bulb and mount with plug (I had one from Ikea that I removed the shade from — I believe I paid less than $6)
• Standard office paper
• Standard white school glue
• Scotch Tape
• Scissors, ruler, knife, etc.

Total out of pocket cost for me (since I had the camera equipment, tools, and lamp) was less than $3.

The entire device is enclosed in a large box (approximately 10″ L x 11″ W x 18″ H).  The flash (and fluorescent light) is at the bottom of the box, then there are two layers of diffusion material, and finally a clear viewing window is at the top of the box.  The camera is connected to the flash with a wireless trigger to allow high quality images with minimal blurring from camera shake.   The flash sits (unattached) on the bottom of the box, and a fluorescent light is mounted on the side of the box (not shown in the diagram or these first shots) to allow negative viewing and to aid the auto focus of the camera.

The box I chose was soymilk box from my local Costco — quite sturdy, and a perfect size and shape.  I cut off two of the top flaps and trimmed the other two to provide a sturdy place to mount the plexi. Then, I covered the inside of the box with white office paper — this was easily the most time consuming portion of the project since I ended up doing two layers over pretty much the entire inside surface.  It took me a couple of hours of work (while watching a movie).

Once the paper dried overnight, I taped two layers of office paper across the inside the box for diffusion.  The lower layer is about 7 inches from the bottom of the box while the top layer is about an inch from the top (although I honestly should have put it about an inch lower — more on that later).  The result is nice even diffusion of light when the flash is centered in the bottom of the box:

Admittedly, the continuous light source was an afterthought, but a very good one.  At first, I thought about just laying the bare light bulb in the bottom of the box, but quickly decided against it because even fluorescent lights get pretty hot.  Please don’t burn down your house with this project!

So, instead, I cut a hold in the side that was off-center, towards the top of the lower cavity.  This location is designed to avoid blocking the flash and to put more direct light on the first diffuser to make sure enough light reaches the top of the lightbox.

The light itself was very easy to mount since it comes with a plastic screw-on flange (this part normally screws onto the plastic shade).  Here is the inside view:

I chose a 11W fluorescent (60W equivalent) for my box, but I think you can easily bump up the power to a 100W equivalent using this mounting scheme without danger of fire.  Incandescent bulbs might produce a more pleasing white balance, but be careful because they generate a lot more heat and the box is very flammable!

Usage and Results:

So, how does it work?

Surprisingly well!  The two diffusion surfaces provide nice, even light across the entire viewing area.  In hindsight, I probably should have gotten a bigger box so that it’d be possible to do a full proof-sheet (approx 8×10) in one shot.  But it is not a big deal to just shoot each sheet of negatives twice — once for each side (three by two 6×6 medium format negatives).  Here is a proof sheet where I squeezed in three by three frames with minimal editing:

A 60W bulb provides plenty of illumination as for continuous viewing as long as the room is relatively dark.  In brighter rooms or outside you might like a brighter light.  Considering the light has to pass through two sheets of paper, it is quite good.  The paper itself though does not provide a completely uniform diffusion surface.  For instance, in the full frame shot below, you can see the mottling and texture in the paper:

The general design (placing the top diffusion sheet an inch below the film surface) is designed to place this mottling outside of the depth of field.  But, for large area shots (i.e. proof sheets) and medium apertures (f/8 to f/16) an inch away does not eliminate all the texture.  If I had to do it again, I’d place the top sheet two inches down to give me a little more leeway.  For now, I’ll just keep this in mind and try to use a lower flash power and larger aperture (to reduce depth of field).

Speaking of depth of field and flash power, I was actually very surprised by efficiency of the flash in this setup and the evenness of the illumination.  Yes, near the edges it loses a tiny bit of intensity (see the above image), but the center of the shot is quite uniform, especially over a single medium format frame.  And most of these shots were taken at 1/8th power on my Sunpak 383 with ISO 100 and f/16!  Yes, f/16!  So, in the future, I’ll probably drop proof sheets to f/11 and 1/16th power to reduce the mottling artifacts, but keep using 1/8th power and the smaller aperture for single frames to decrease issues with film flatness.

All my proof-sheet shots were taken with my Tamron 17-50mm f/2.8 and the single frames were taken with an antique Canon 100mm f/4 Macro (with FD-EOS adapter).

Processing:

Scanning negatives in this way puts a lot of the load onto processing, which tends to be a bit finicky.  Yet, at the same time, it is rather forgiving.

The basic idea is simple: take the shot keeping everything in the histogram, invert the image, then adjust the shadows, highlights, and contrast accordingly.

The finicky aspect comes in when thinking in terms of the dynamic range of the input image.  Based on how your negatives are exposed, I think you’ll find that 24-bit color (8 bits per channel) from JPEGs will not give you enough flexibility to adjust the exposure to your liking.  Shooting RAW (12 bits per channel) is pretty much a must.  In some shots, I found I needed to expand a very narrow range (sometimes an eighth of the available intensity range) and in other shots I found that I had to adjust the exposure a stop or more.  While you can fine tune that as you take the picture, I think it would be hard to really nail it consistently without using RAW.

For processing, I use Bibble Pro.  Of course, Bibble does not have a dedicated ‘invert’ option — I think most RAW processor programs don’t support negative inversion.  But, Bibble Pro 4.10 does have “Andy”, a black and white simulation with multiple types of film, paper, and the all important ‘See Neg’ button that lets you invert the image.  While I could do the same thing with Paintshop Pro or Photoshop, I find it a lot easier (and faster) to process the images in Bibble without dragging around huge TIFF files.

Also, I DO NOT recommend using this type of scanner for color negatives.  Sure, go ahead and try it, but office paper produces a bit of a blue color cast and I expect it will be very difficult to get color correct from a film negative.  Honestly, I’ll probably try it at some point, but I expect it will result in some very strange color images!

For black and white though, there are a ton of settings — everything from intensity curves in Bibble to the BW conversion options to exposure on my digital camera to exposure on the film camera to the film developing!  Luckily, you can usually compensate digitally from a RAW image and tune it to look like you want it.  For example:

I’m pretty happy with the scanner and the images that result, and I’m going to get started making digital proof sheets and scanning specific images I like over the next few days.

And, of course, shoot and develop more images!

This is the final post in a series of four related to cleaning my used Yashica Mat 124.  The first post in the series describes the task in more detail and includes links to all of the other posts.

A common complaint with used Yashica Mat 124 / 124G cameras is that that meter is inoperative.  On my camera, the eBay auction stated that the meter no longer worked, but I suspect the seller never even bothered to try a new battery in it.  So, it is often worth asking if they’ve tried the meter with a good battery before you determine that it no longer works.

The problem is that the 124 and 124G are designed to run off a mercury 625 cell (generating a nominal 1.4 volts) that has been banned due to mercury content.  As a result, it is very hard to find 625 batteries for these cameras, and even if you can find one, can you really deal with the guilt of putting poison into the environment?  The replacement 625, if you can even find one, is typically alkaline with a nominal (and unstable) voltage of 1.5 volts, which causes the 124 metering to read incorrectly (too high, I believe, causing under-exposed photos).

The best replacement (chemically) is a zinc-air battery, but zinc-air batteries are not commonly sold in the 625 size.  A readily available alternative is the zinc air 675 battery, that produces the needed 1.4 Volts stably across its life cycle but does not fit in the Yashicamat 124(g) straight out of the box.  The image below depicts this physical difference:

625 mercury battery (left) and 675 zinc-air battery (right)

As you can see, the 625 has a much larger diameter and slightly more height.  There are a variety of strategies to get the 675 zinc-air batteries into older cameras – this great page at KYPhoto describes many of the ways.  Probably the easiest are Wein cells — newer zinc-air batteries with the right size specification.  But, Wein cells tend to be harder to find and more expensive than similar batteries because they are a specialty commodity.

The approach I’ve taken is to adapt a 675 battery to fit the space of a 625 battery — Rick Oleson has a good page on this which is similar to my approach.  The basic idea is to increase the diameter of the battery (by placing a spacer in the battery holder) and increase the height slightly since the 625 is usually held by the lip around the outside (not the positive terminal face) but the 675 does not have the lip.  In the image above, you can see the battery holder on the 124 (which includes a metal screw-in top).  But, where Rick Oleson uses wire, I use one of these and some aluminum foil:

Your local hardware store has a wide variety of faucet O-rings that work great for the spacer with the bonus of well-calibrated size and non-conductivity.  I used a 7/16″ I.D. and 5/8″ O.D. ring and it cost me less than $1 for two of them.

Battery-wise, I spent $6 at my local Fry’s Electronics for a pack of 6 Energizer 675 zinc-air batteries:

The image that started this post shows the materials used.  Just insert the o-ring into the hole in the camera (it will fit snugly), place the battery on top of the foil on the cap, and screw the cap back in.  I found it best to hold the cap up with the camera battery holder upside down keep stuff from falling apart.  The battery goes in snugly and securely and automatically centers itself.

And, the end result is a working match-needle meter:

Note the red needle, driven by the battery and sensor, that you need to line up with the yellowish-green ‘hook’.  Easy, costs less than a buck for the parts and a buck a battery, and works pretty well!

Update:  Well, I spoke a little too soon on things working well.  My meter has been malfunctioning and reading low.  Sometimes, when I open the hood up it does not turn on, and sometimes even when it does work it twitches all over the place.  I need to look into it more, but it is likely either the battery contact (which is somewhat corroded — I originally sandpapered it, but I don’t think it took) or, more likely, the switch in the hood is flaky.  I’ll open it up in the near future and see what I can do.  The camera is so much easier to use when the meter is operable, even if the meter is a little imprecise!

Update #2: (10/25/09) The foil ended up being less than reliable, since it tends to compress over time and it may cover the air holes of the battery (causing inconsistent metering).  Instead, I found a twisted spiral of copper wire (22 AWG) does a good job of spacing the battery without restricting airflow: