Polaroid 600 film actually fits in an SX-70 camera pretty easily. The problem with using 600 film in the SX-70 is that it is four times more sensitive than SX-70 film. Without modification, all your photos taken with 600 film would be overexposed. To correct this problem, we are going to adjust the camera by two stops. We will use a one stop neutral density filter to cover the lens, and we will remove the neutral density filter that covers the photocell. If you are wondering why we are adjusting by two stops when the film is four times faster, here is a quick math lesson. One stop is equivalent to doubling (or halving depending on which direction you are going) the amount of light. So, 2x2=4. Alright, lets get started.

Supplies:
You are going to need a few supplies in order to make this modification to your SX-70 camera. You will need a clear cd case, an x-acto knife and a one stop neutral density filter. Depending on the neutral density filter you find, you may also need some glue to affix the lens to the camera.

Step 1
The SX-70 camera has a photocell on the front of the camera to the right of the lens. This is the camera's "eye" which it uses to sense how much light it is looking at. It is looking through a neutral density filter. We are going to remove that filter so that the camera thinks that what it is looking at is two times brighter than what it actually is. This will save us one stop. Here's what you do:

Remove the filter retaining ring (the little chrome ring which surrounds the photocell) by gently pushing the tip of a small knife under the edge and popping out the ring. Remove the small round neutral density filter. While you have the filter out of the way, it is interesting to see how the light/dark adjustment works by covering and uncovering the light sensor.

Next you want to cut a piece of clear plastic to go in place of the neutral density filter. This is where the clear cd case comes into play. This is a little harder than you would think. If you try cutting the plastic with scissors, it will crack and splinter.

In order to get a nice circular piece of the plastic you have to cut it out with a sharp x-acto knife. I cut out a piece just slightly larger than the old filter and then sanded it down to a more round shape.

Once you have your piece of clear plastic, you can put it into the ring and try to place it back on the camera. You will notice that the cd plastic was a little thicker than the old filter, so this is going to be a tight fit.

You will probably have to sand the edges a little more so the plastic can sit a little closer to the photocell. Now the hard part is done and you are ready for step 2.

Step 2
In order to gain our second stop, we need to add a one-stop neutral density filter in front of the lens of the SX-70 camera. While there aren't threads on the front of the lens, it is possible to screw a filter in if you "force" it. The size of filter that you need is 28mm.* There is only one problem with screwing a filter on this way: you can't fold the camera down because the lens sticks out too far in front of the lens.

I plan on folding my camera down, so I decided to remove the glass from the filter and attach it directly in front of the lens. To get the glass out of the aluminum part of the filter, I used a needle nose pliers to bend the aluminum away from the filter. Once the aluminum was bent pack, the glass came out.

I suppose there are many ways to actually attach the glass, but I decided on hot glue. I was afraid that if I used super glue, the glue would run onto the lens and I wouldn't be able to clean it off. Hot glue worked just fine.

Step 3
We are done with all the modifications to the camera and now all you have to do is load the film. When you look inside the empty space where the film will go, you will see a piece of square metal sticking up. This spring is what catches on the two center "nubs" of the 600 film cartridge.

You can either cut the nubs off, or you can use a card, or old Polaroid picture to cover the nubs as you slide the film in. First, insert the card in the empty camera.

Next, insert the film cartridge.

When the film has passed the spring, you can remove the card and insert the cartridge the rest of the way.

Finally close the camera. When the door closes, the camera should eject the dark slide. You are now ready to use your modified SX-70 camera!

*(At this point in the mod, I discovered that I already had a couple neutral density filters that were 28mm. What are the odds? The filters were made for my Nikon Coolpix 995. Unfortunately, I only had an ND4 and an ND8 which are equivalent to two stops and four stops respectively. I decided that rather than purchase a one-stop filter, I would use the two stop ND4 filter. I put the filter back in front of the photo cell since the ND4 filter gave me the two stops that I needed.)