2-Perf vs 3-Perf vs 4-Perf: 35mm Film Formats Explained

INTRODUCTION

The starting point when it comes to choosing which format to shoot a movie on is between digital and film. If film is selected, by far the most popular film format is 35mm. But what you may not know is that there are then 3 further format choices that need to be made between: 2-perf, 3-perf or 4-perf. But what is a perf and how does it affect both the budget and how the footage looks? Let’s find out.

WHAT ARE PERFS?

The manner in which a piece of 35mm film is exposed is determined by the negative pulldown. This is described in what are called perfs. Perfs stand for perforations and are the little holes that you see in the film that span the length of each individual frame. 

These holes align with sprockets, which turn in order to mechanically pass an unspooling roll of film vertically through the camera. The film is exposed when it is hit by light which is let through the lens. 

35mm film frames can be shot with either four vertical perfs, 3-perf, or 2-perf. As the width of a 35mm frame is standardised to a size of 24.9mm, the number of perfs only effect the height of the frame that is recorded - with 2-perf capturing the skinniest surface area, and 4-perf capturing the tallest surface area.

Exposing a larger area of film to light is kind of like the digital equivalent of recording at a higher resolution - the larger the area the more clarity and higher fidelity it will be. However, the larger the exposure area, the more film needs to be used and the more you will need to pay for film stock and development. So perfs affect both the cost of shooting as well as the quality or fidelity of the image.

The motion picture camera that is used must be specifically set to record frames with a certain number of perfs by adjusting the speed at which the film runs through the camera as well as the height of the gate that lets through light. Most cameras can record either 4-perf or 3-perf, while only specific cameras can record 2-perf frames.

There are two different steps to the filmmaking pipeline. Capturing images on film with a camera and projecting those images on film by passing light through them.

Image capture can happen on either 4, 3 or 2-perf, however 35mm film projectors are set to work with a 4-perf film print. This means that if you capture film in 2 or 3-perf, you would still need to print the final 35mm projection roll in 4-perf frames.

However, now that digital projection has taken over, it’s possible to capture 35mm in either 2, 3 or 4-perf, scan the film negative and then work with the scan in the same way as a digital file - which can later be sent out to cinemas that use a digital projector or for online distributors to upload the file and stream it digitally.

4-PERF

In the late 1800s and early 1900s when motion picture film technology was undergoing development, 4-perf 35mm film capture and projection emerged as the industry standard. This produced a tall aspect ratio of 1.33:1. 

4-perf offers the largest exposure area of 35mm film at 18.7mm tall. Because more surface area is used the film grain will be smaller and the image will be of a higher quality. 

This large surface area also allows lots of possibilities for aspect ratios. When shooting Super35 with normal sphercial lenses the frame can be used for taller aspect ratios like 1.33:1 or the top and bottom can be cropped to get widescreen aspect ratios like 1.85:1 or 2.40:1.

Before digital, this crop would have been done by printing the final film to a different ratio with a letterbox, or by using a narrower plate that chopped off the top and bottom of the frame when projecting. Now this can be done by scanning the negative and using software to crop the image.

4-perf can also be used with anamorphic lenses. These lenses squeeze the image by a factor of 2, to around a 1.2:1 aspect ratio, so that it is captured as a tall, compressed film frame. It is then later de-squeezed by a factor of 2 to get it to a widescreen 2.40:1 aspect ratio.

Because this method uses such a large portion of the tall 4-perf frame, anamorphic negatives have a higher fidelity and low amount of grain.

Another advantage of 4-perf is that when shooting Super35, the extra recorded area on the top and bottom of the image, that will be cropped out, can help with VFX work, such as tracking.

A disadvantage of 4-perf is that more film must run through the camera faster, which makes it noisier. This also means that it uses the most film out of the 35mm formats, which means more money must be spent on buying film stock and developing it.

It also means that a 400’ roll of film will only be able to record for a mere 4 minutes and 26 seconds, before a new roll must be reloaded into the camera.

3-PERF

In the 80s, cinematographer Rune Ericson collaborated with Panavision to produce the first 3-perf mechanism for 35mm cinema cameras. 

Shooting each frame 3 perforations tall as opposed to 4, produced a less tall frame with a height of 13.9mm and an approximate aspect ratio of 16:9. 

When shot with spherical lenses this negative could easily be ever so slightly cropped to get to a 1.85:1 aspect ratio, or more cropped to get to a 2.40:1 aspect ratio. 

Because of the lack of height of the frame, 3-perf wasn’t suitable for using 2x anamorphic lenses, as it would require too much of the frame width to be cropped and therefore go against the point of getting a high quality anamorphic image. Therefore, 3-perf is best when used with spherical lenses.

However, it is possible to use the much less common 1.3x anamorphic lenses with 3-perf film, as they squeeze a 16:9 size negative into a widescreen 2.40:1 aspect ratio.

Due to the decrease in recording surface area, grain will be slightly more prominent in the image than when using 4-perf.

The main reasons for shooting 3-perf rather than 4-perf are financial and practical. 3-Perf uses 25% less film - which means a 25% reduction in the cost of both film stock and processing of the film at a lab. 

It also means that the camera can record for 33% longer than 4-perf. So a 400’ roll gives a total run time of 5 minutes and 55 seconds before the camera needs to be reloaded. This is practically useful especially when shooting during golden hour or in situations where taking the time to reload a camera might mean missing a shot.

2-PERF

2-Perf, first called Techniscope, gained popularity in the 60s when it was used to shoot lots of Spagetti Westerns. These movies were often done on quite low budgets, yet wanted a wide 2.40:1 aspect ratio to frame the characters in sweeping landscapes.

2-Perf does this by further cutting down on the vertical recording height of the negative, taking it to 9.35mm, creating a native widescreen aspect ratio.

At the same time, this reduction in frame size also equates to a reduction in the amount of film that needs to be used. Since it is about half the height of 4-perf, about 50% can be saved on purchasing film stock and processing film. Therefore 2-perf was a great solution to both save money and create a widescreen aspect ratio.

It also basically doubles the recording time of each roll, allowing you to get 8 minutes and 53 seconds with 400’ of film. This means that it’s possible to either roll for longer takes, or that many more short takes can fit on the roll before needing to reload the camera. 

Because it is so skinny and lacks height it’s not possible to use this format with anamorphic lenses - not that you would need to since you get the same aspect ratio by using spherical lenses. 

It’s also only really suitable for using this aspect ratio, as getting a taller ratio would require cropping into the image far too much and increase how the film grain looks significantly.

Although it has the same ratio as anamorphic, it has a different look. Because the surface area is much smaller than 4-perf, the grain shows up as much more prominent. 

In the modern era where film stocks have become much finer grain and cleaner looking some cinematographers like using 2-perf to deliberately bring out more filmic texture and make the footage feel a bit more gritty.

I’d say 2-perf 35mm is basically a middle ground between a cleaner 4-perf 35mm look and a grainier 16mm gauge stock.

CONCLUSION

How many perfs you choose to shoot on has an effect on a number of factors. 

4-Perf records onto a greater surface area, which looks cleaner, with less grain, can be used with both anamorphic lenses, or spherical lenses, and has room to crop to different aspect ratios.

However, this comes at a higher cost, with a camera that makes more noise and very short roll times. 

On the other hand 2 and 3-perf, use less of the negative, which makes the image a bit grainier, isn’t compatible with 2x anamorphic lenses, and limits the amount of taller aspect ratios you can choose from. But, it’s much cheaper and the camera can roll for longer.

In this way, the choice of 35mm film format, is another technical decision which filmmakers can make that effects both the look and feeling of the image, as well as providing certain technical limitations and advantages.