If you have been shooting medium format film for any length of time, you already know the stomach-dropping feeling. You finish a great roll of portraits, wind it off, and pop open the back of your camera. Instead of a tightly wound, neat little cylinder of film and paper, you are greeted by an unwieldy, expanding mess that looks like a paper slinky trying to escape its spool.

Congratulations, you have got a "fat roll."

When you get a fat roll, the backing paper isn't pulled tight against the plastic flanges of the take-up spool. Because 120 film doesn't sit inside a light-tight metal cassette like 35mm film does, its only protection from the sun is the tight wrapping of its backing paper. When that wrap is loose, light spills over the edges, creating those dreaded orange and red burn marks along the borders of your negatives. Often, a fat roll is so thick you can't even lick the adhesive band to seal it shut.

It is incredibly frustrating, especially when you think you did everything right. But what actually causes a fat roll? Is your beloved vintage camera breaking down, or are you just loading it wrong? Let us break down the usual suspects.

Suspect Number One: Your Loading Technique

I will be completely honest with you: nine times out of ten, a fat roll is just the result of sloppy loading. I say this from personal experience, having ruined my fair share of Lomography color film because I was rushing to load my Yashica Mat on a windy beach.

When you pull the paper leader across the film plane and thread it into the empty take-up spool, it relies entirely on tension. If you just thread it in and start blindly winding the crank, the paper might catch right away, but it will wrap loosely. Here is how you fix your technique:

• Use the thumb brake: As you thread the leader into the take-up spool, keep your left thumb pressed firmly against the full roll of unexposed film (the feed spool). You want to create resistance. When you turn the advance crank with your right hand to reach the start arrow, your left thumb should be forcing the paper to pull tight and flat across the camera back.
• Check for a straight feed: When you slot the paper tab into the take-up spool, make sure it is perfectly centered. If you tuck it in at an angle, the paper will climb up one side of the spool flange as it winds. By the time you get to frame ten or twelve, the paper will be bunching up and forcing itself outward, creating a fat roll.
• Don't let go too early: Maintain that thumb pressure until you close the camera back. The pressure plate on the camera door will take over the tension job once it clicks shut.

Suspect Number Two: The Take-Up Spool

Not all 120 spools play nicely with every camera. This is a quirky, somewhat annoying fact of analog life. A take-up spool is just an empty plastic (or sometimes vintage metal) spool left over from your last roll of film. Because you constantly swap them out, you are mixing and matching brands constantly.

Sometimes, the slot on a plastic Kodak spool is just a hair wider than your specific camera's winding key likes, causing it to slip. Other times, the plastic flanges on a used spool might be slightly warped or bent inward from bouncing around in a camera bag for three years. If the flange is bent, the film will snag on the edge as it winds, totally messing up the tension.

If you keep getting fat rolls despite using the perfect thumb tension technique, try keeping a specific spool that you know works perfectly in your camera. Next time you finish a roll, do not give that good spool to your lab. Ask them for a junk spool to swap, or spool the film onto a different core in a dark bag.

Suspect Number Three: The Camera Back or Insert

If you are meticulously holding tension and using pristine spools but still getting fat rolls, it is time to look at the hardware. Vintage medium format cameras are incredible mechanical achievements, but they are also decades old. Parts wear down.

Most medium format cameras, particularly modular SLRs like the Mamiya RB67 or the Hasselblad V-system, use removable film backs or inserts. Inside these inserts are little metal leaf springs that sit under the feed and take-up spools. Their entire job is to provide friction so the film doesn't unspool freely.

Over fifty or sixty years, those friction springs can lose their bend and become flat. If the spring under the feed spool is too weak, the film roll basically goes into free-fall when you crank the advance lever. The take-up spool pulls, but the feed spool gives no resistance, resulting in a loosely wrapped fat roll. If you suspect this is happening, you can often test the tension with the insert out of the camera. The spools should feel slightly stiff to turn by hand, not completely loose.

Another classic hardware mistake happens with cameras that shoot both 120 and 220 film. 220 film does not have backing paper running the whole length of the roll, making it much thinner. Cameras handle this by adjusting the pressure plate. If your pressure plate is set to 120 but you are somehow shooting a rare roll of 220, the lack of pressure will ruin your tension. Always double-check your pressure plate settings.

Suspect Number Four: The Film Brand

Finally, we have to talk about the film itself. Different manufacturers use different machines, and more importantly, different types of backing paper. Over the past few years, Kodak has experimented with different paper thicknesses to solve some emulsion-scratching issues, which occasionally resulted in paper that felt stiffer or thicker.

Some European brands or experimental films use very thick paper bases. I have noticed that with certain thick-paper films in my older crank-advance cameras, the sheer bulk of the paper seems to fight against the spool flanges near the end of the roll. It is not necessarily "broken," but it requires you to be hyper-aware of your loading tension.

How to Save a Fat Roll in the Field

So, you opened the back and saw the dreaded fat roll. First rule: Do not panic, and whatever you do, do not pull it tight right there in the daylight.

A lot of people instinctively grab the loose tail of the paper and yank it hard to tighten the spindle. In the photo world, this is called "cinching." Because 120 film rests directly against its own paper, violently pulling it tight causes the layers to grind against each other. Almost every time you cinch a roll, you will leave hundreds of tiny static-strike scratches right across the emulsion of your photos. You might fix the light leak, but you'll ruin the images anyway.

Instead, gently cup your hand around the loose roll to shield it from ambient light. Take it to a dark bag, a darkroom, or at least a completely pitch-black closet. Once you are in total darkness, carefully unroll the film an inch or two and slowly rewind it tight by hand. Then, seal it up with tape or a rubber band before turning the lights back on.

Ready to Step Up Your Medium Format Game?

Medium format photography forces you to slow down and respect the mechanical process of shooting film. Getting a fat roll is just an analog rite of passage. Once you master the loading tension and make sure your gear is humming along, nothing beats the massive, beautiful negatives that a good 120 camera produces.

If you are finding that your current camera's film back is just too worn out, or you are itching to dive into the world of larger negatives for the first time, you might want to explore some different bodies. You can browse our current selection to find a medium format camera that fits your shooting style. And if you are jumping to a fully manual modular system, it is always a good idea to grab a dependable light meter to make sure those crucial, expensive medium format frames are perfectly exposed every single time. Keep practicing your loading, and happy shooting!