Modify a Canon EOS-300 into a manual M42 mount camera!

You love your M42 manual lenses, but fed up with your heavy, stinking old SLR? You want a decent motor drive and flash on your camera?.. Hmm. Today we'll convert an EOS-300 to take your old M42 lens stock and install a split-image screen to ease manual focusing.

M42 lenses are so 1970s. They are built to last. And among them you'll find spectacular ones that rival modern lenses in so many ways. Check out these:
- Carl Zeiss Jena - Flektogon 35mm f2.4,
- Pentax Super-Takumar 50mm f1.4,
- Carl Zeiss Jena - Sonnar 135mm f3.5, and many others.

A few years ago, you could get them for half the shipping price on ebay. Nobody wanted them. People loved their 'wonderful' autofocus/autoexposure Canons, Nikons, Minoltas... Now people went digital, and experimenting is virtually free. So they started looking into alternatives. That's why we have a boom in old M42 lens market! People love them on their Canon digital camera bodies. I said Canon, because the lens register space in Canon DSLRs allows using an adapter to convert M42 to EF lens mount. You focus manually, set your aperture manually, and use 'aperture priority' mode for auto-exposure.

Since everybody is into DSLRs, mass production film cameras go dirt cheap on ebay. I mean some lower end modern Canon EOS series and some Nikons. You can get a mint EOS-300 body for $40 including shipping. EOS-300 makes a great light body to use for your street photography. Put a wide-angle M42 lens on it, and you'll have a very compact, reliable, quick camera. It has 1.5 fps burst shooting. Built-in flash. Reliable auto exposure. Low power consumption. For its price, these are great features.

However, the mirror mechanism slaps some M42 lenses, we have to modify the mirror. The original focusing screen doesn't help you for focusing manually, so we'll change it into a split-image screen. The M42-EF adapter needs to be taken off each time you change a lens. I prefer it to stay on the camera, so we'll solve that problem, too.

Tools needed: Utility knife, pliers, watchmaker screwdrivers, fine-grit sandpaper, adhesive tape...
Parts needed: Canon EOS-300, M42 lens, M42-EF mount converter, an old SLR focusing screen (F-1)...

Below are the photos of the camera before and after the modification!.. In the middle you have the M42-EF mount adapter.

Step 1: Start with the focusing screen!

In this step we'll take out the existing focusing screen from EOS-300 and modify an old focusing screen to fit into our camera. For the split-image focusing screen you have to dig into an old SLR camera to salvage a focusing screen. I had an old Canon F-1 modular focusing screen laying around, so I decided to make use of it. This was an expensive decision since I could sell it on ebay for at least $15. Well, I want this camera now! :-)

The first photo is from the original focusing screen on Canon EOS-300. The second photo is the split-image focusing screen that we'll fit into our EOS-300.

Comments

[joro999]

That's impressive  but carl zeiss lens are build for old practika camera *45.5 mm...better is to use Optical M42 Lens - Canon EOS digital camera adapter

[thearchitect]

Well, this Carl Zeiss Jena is M42, like few other Carl Zeiss lenses (Flektogon 35, Tessar 50, Pancolar 50 and 80, and Sonnar 135). Are you confusing them with Carl Zeiss Jena lenses in Praktica B bayonet mount?

K.

[okto]

A tip: when collecting the bits for this Instructable, try to find an EF-to-M42 adapter that fits flush into the camera (doesn't have that flange), so you can focus all the way to infinity with all lenses. ^_

[thearchitect]

Well, the one I have is too thin, so it focuses well beyond infinity which I really don't like... At manual focus forum (http://forum.manualfocus.org/index.php) there are people who found better crafted EF-M42 adapters... Check'm out!.. Cheers. K.

[okto]

I've always thought that the ability to focus beyond infinity is an indicator that "infinity" is an inaccurate term, lens-wise. You can't have something behind the furthest thing.

[radiorental]

Very nice instructable, well documented. Is it safe to say that a split focusing screen is going to be hard to find?

[thearchitect]

Thanks! Finding split focusing screen is not a big deal I guess. People are selling lots of broken camera bits and pieces on ebay. It shouldn't be a big deal to take a focusing screen out of them. The only problem is finding one with correct size/thickness. Since EOS-300 has 90% coverage for viewfinder, most of the old focusing screens will be larger anyways. Good luck!

[manuel.flury]

That's impressive ! Congratulations.