I still remember the first time I held a Hasselblad 500C/M. I was practically vibrating with excitement, but also completely terrified of messing up the film loading process. If you are coming from the 35mm world, 120 film looks kind of like an alien artifact. There is no neat little metal canister. There is no easy slot to just blindly shove the film leader into before slamming the camera door shut. It is just a roll of paper, some plastic spools, and a whole lot of room for error—or at least, that is how it feels on day one.

But honestly? Once you do it a few times, loading a medium format film back becomes second nature. It becomes one of the most tactile, satisfying routines in analog photography. That mechanical sequence of winding, clicking, and advancing is enough to make anyone fall in love with these heavy vintage bricks. Today, we are going to walk through how to load a 120 film back, specifically focusing on the two major hitters in the vintage world: the Hasselblad A12 system and the Mamiya RB67/RZ67 backs. Grab a test roll, take a breath, and let's figure this out together.

The Magic of Modular Film Backs

Before we dive into the nuts and bolts, let's talk about why these film backs are so incredibly cool. When you shoot a 35mm camera, you are committed to whatever film is in that camera until you hit frame 36. If you have ISO 100 color film loaded and you walk indoors, you are basically out of luck. Medium format cameras like the Hasselblad V-system and the Mamiya RB67 use modular backs, meaning the film lives in a detachable box on the back of the camera. You can carry three different backs in your bag—one with black and white, one with color negative, and one with slide film—and swap them out mid-roll without ruining a single frame. It is a total game changer for creative freedom.

Understanding 120 Film Basics

If you have only ever shot 35mm, you need to understand how 120 film is built before you try to load it. There is no canister here. The film is literally just a long strip of emulsion taped to a longer strip of opaque backing paper. It is entirely rolled tightly around a plastic spool.

Because there is no canister, when you finish a roll of 120 film, the spool you started with is completely empty. That empty spool now becomes your "take-up spool" for your next roll. You will always be migrating an empty spool from one side of the film insert to the other. Also, light leaks are the enemy of 120 film. The only thing stopping the sun from ruining your photos is how tightly the paper is wound around the spool. Always keep your thumb pressed firmly against the roll of film while you are handling it so it does not uncoil like a snake springing out of a joke peanut can.

How to Load a Hasselblad A12 Film Back

The Hasselblad A12 is arguably the most famous film back in the world. It looks incredibly elegant, but its loading path is a weird little maze. Do not rely on memory the first time; follow these steps.

• Remove the insert: Fold out the little D-ring key on the right side of the film back, twist it counter-clockwise, and pull the entire insert straight out.
• Move the empty spool: Take the empty spool from your last roll and snap it into the bottom position (the take-up side) of the insert.
• Load the fresh roll: Snap your new roll of 120 film into the top position. Make sure the paper leader is feeding toward the back of the insert.
• Thread the film: Pull the paper leader over the top roller and feed it under the flat metal clamp on the back of the insert. When you do this, the black side of the paper (the side where the film actually lives) must be facing outwards. If you see the colored side with the branding and graphics on the back plate, you have loaded it upside down.
• Feed the take-up spool: Pull the paper around the bottom roller and insert the tip of the leader into the slot on your empty take-up spool.
• Line up the arrows: Gently turn the knurled knob on the side of the insert to wind the film. Keep turning until the thick start arrow on the backing paper perfectly aligns with the red triangle painted on the side of the insert. This is the most crucial step!
• Lock it in: Slide the insert back into the shell, push the D-ring key in, and turn it clockwise to lock it. Finally, fold out the winding crank on the side of the shell and wind it continuously until it physically stops on frame number 1. You are ready to shoot!

How to Load a Mamiya RB67 / RZ67 Film Back

The Mamiya backs operate on a very similar principle, but they are a bit bulkier and feature a straight-shot film path instead of the Hasselblad's wrap-around maze. Here is how to conquer the Mamiya.

• Open the back: Depending on your specific model, you will either push two little tabs or squeeze a latch to pop open the back shell. Remove the insert completely.
• Move the empty spool: Just like with the Hassy, take your empty spool and move it to the take-up side. Snap your fresh roll into the supply side.
• Thread the paper: Pull the leader directly across the back of the pressure plate. The black side should be touching the metal plate, meaning the branded side is facing you. This is the opposite of the Hasselblad!
• Feed the take-up spool: Tuck the leader firmly into the slot on your empty spool.
• Align the start mark: Use your thumb to manually roll the gear on the side of the insert until the arrows on your film's backing paper line up with the red or white start dot on the insert. Keep tension tight with your thumb so the paper does not go slack.
• Close and advance: Put the insert back inside the outer shell, snap the door shut, and use the camera's advance lever to wind until the counter hits "1". Boom. Done.

Three Golden Rules for Medium Format Beginners

No matter what system you end up choosing, there are a few things every medium format shooter eventually learns the hard way. First, always load your film in the shade. Direct sunlight can easily creep over the edges of backing paper and fog the edges of your film. If you cannot find shade, just turn your back to the sun and cast a shadow over your camera with your body.

Second, do not lose your dark slide! You cannot remove a film back from the camera body unless the safety dark slide is pushed all the way in. It is a brilliant safety mechanism so you do not accidentally expose your film to light, but if you drop your dark slide in a grassy field, you will not be able to swap backs until you find it.

Finally, save the little sticker that wraps your fresh roll! Most modern 120 films have an adhesive strip at the end of the roll that you lick or peel to seal it after it has been shot. Keeping the roll tightly sealed in your bag prevents "fat rolls" and keeps your precious exposures safe from light leaks on the trip home.

Ready to Expand Your Vintage Kit?

Moving up to medium format usually means you are going to need a few solid accessories to get the most out of your massive negatives. Because these older modular cameras rely completely on manual settings, having a trustworthy pocket light meter is almost a requirement. If you are looking to treat yourself to a reliable setup, or you want to browse some fresh options for your gear bag, I highly recommend running a quick search for light meters or picking out new medium format cameras over at the Old Cams by Jens store. They have an excellent, hand-checked inventory that takes the guesswork out of buying vintage. Have fun out there, keep your film wound tight, and enjoy those huge, beautiful negatives!