The SX-70 was a folding single lens reflex Land Camera produced by the Polaroid Corporation in the 1970s. It was the first instant SLR in history, and the first camera to use Polaroid's new integral print film, which developed automatically without the need for intervention from the photographer - this was a revolution at the time, and a precursor to today's 600 and Spectra films.
The SX-70 utilized a folding body design, a 4-element 116mm F/8 glass lens, and an automatic exposure system. The lens could close focus to a distance of 10.4 inches, and had shutter speeds ranging from 1/175 to more than 10 seconds. There were a variety of models beginning in 1972 with the original SX-70, though all shared the same basic design. Later models were often equipped with a sonar autofocus system, and the Model 3 departed from the other models as it was not an SLR, instead using a viewfinder cut into the mirror hood - though all other mechanics were identical.
All models feature an electronically controlled 'flash-bar' socket across the top of the camera, for insertion of a 10-use set of flashbulbs. Polaroid - and other companies - also made external flash units that plugged into this socket.
As well as the folding SLR model, a variety of non-folding, 'consumer'-type models were released that also used to SX-70 integral film.
Accessories and Add-Ons
Though expensive, the SX-70 was popular in the 1970s and retains a cult following today. As such, many unique accessories were produced for the SX-70 including:
- Telephoto lens - A teleconverter (pictured below) which gave an effective 1.5x conversion (to 174mm)
- Close-Up kit - a set of macro-photography lenses coupled with flash adaptors/diffusers
- Self-timer - a clockwork timer that clips onto the side of the unit, covering the shutter release button
- External flash - Several models were made, including several by third parties.
- Tripod Adaptor - Many earlier models of the SX-70 did not have tripod mounts built-in.
One feature of the SX-70's integral print film is its ability to be manipulated while still developing. Because it is an instant film and develops over a period of several minutes, artists are able to "push" the emulsion material around the photograph to produce effects somewhat like impressionist paintings.
SX-70 Film and Alternatives
The SX-70 cameras were designed to use SX-70 or TimeZero instant film, which came in a pack which was inserted into the camera, and had 10 exposures per pack. The film pack also contained a built in battery which powered the camera. SX-70 film had an ISO (film speed) rating of 125, and was prized by art photographers for a unique quality which allowed the emulsion to be manipulated by pressing on the photo using a blunt object - these "SX-70 manipulations" often have a surrealistic quality. Unfortunately, Polaroid discontinued manufacturing SX-70 film in 2006, so the film is no longer available. This was very sad news to the legion of devoted SX-70 users who prized their unique folding cameras.
Fortunately, there are alternatives that allow one to use Polaroid 600 film in an SX-70 camera - 600 film is widely available at drugstores, so this is indeed good news. Furthermore, because 600 film is much faster than the original SX-70 film, much faster exposures can be obtained which allow the user to take photos in dim lighting conditions without the use of flash. 600 film and SX-70 film are the same physical size, so a 600 film cartidge will fit in an SX-70 camera. Polaroid put small tabs on the bottom of the 600 film cartridge to prevent people from accidentally using the wrong film, so those tabs must be removed to insert the pack into the camera. Alternatively, one can place a playing card or similar under the film pack to aid sliding it into the camera - the card must be removed before closing the camera to allow it to operate.
The larger problem with using 600 film in an SX-70 is that it has a much faster film speed rating of ISO 640, and the SX-70 cameras were designed to expose for the original film which had an ISO of 125. What this means is that simply using 600 film in an SX-70 camera will cause the photos to be overexposed. Fortunately there are ways to make the SX-70 expose 600 film correctly.
Method 1 - Using a Neutral Density (ND) filter over the lens
This is most likely the easiest way to use 600 film in an SX-70 camera. Polaroid produced a two stop ND filter which can be placed over the lens of your SX-70. This filter basically acts like sunglasses for the camera, and darkens the image by two stops so that the camera exposure is correct. These filters are available to order from various vendors through Ebay. The advantage of using this type of filter is that it is a very simple modification to the camera, as the filter simply sticks on the front of the lens. The disadvantage to this method is that the viewfinder becomes much darker, making focusing difficult, and making it difficult to see the subject. Also, the filters are not made of glass, but are made of a thin plastic film which cannot be cleaned, and is not very durable. Furthermore, placing the plastic filter degrades the quality of the image to some extent. This method causes the camera to expose at the original ISO 125, so the benefit of faster exposures from 600 film will not be obtained.
Method 2 - Using an ND filter over the film:
This is a similar approach to method 1, where the exposure is corrected with a 2 stop ND filter. Unlike method 1, this approach involves placing the filter directly over the film pack, instead of over the lens. Sheets of ND film can be purchased, cut to the size of the film pack, and taped or glued on top of the film pack prior to loading it in the camera. The advantage to this method over method 1 is that the viewfinder remains bright, and so focusing and composition is easy. The disadvantage to this method is that there is still some image degradation resulting from placing a filter over the film. Also, it is easy to damage the film when sliding the filter into place. If you do not have the expertise to do this yourself, you can purchase film from a third party manufacturer which already has an ND filter placed over the film. This third party film is known as "SX-70 Blend" film, and is a ISO 640 film with a filter placed over the pack - it is not manipulatable like the original SX-70 film, and is also very expensive compared to standard 600 film, but is a good alternative if you do not wish to do modifications yourself and can afford the expense of purchasing this film.
Method 3 - Removing the Electric Eye filter:
This approach is favored by many SX-70 users, since it requires no added filter in the light path of the camera, and is one of the easiest methods to use 600 film in the SX-70. Be aware, however, that it does not work on all SX-70 cameras. To use an SX-70 this way requires two steps - the first step is to remove the filter in front of the electric eye on the camera. This is easily done by prying off the chrome ring which surrounds the filter using a thin pocketknife or similar object. One the ring is removed, the filter falls out. The chrome retaining ring can simply be snapped back into place, and the filter should be stored in a safe place in case you ever want to restore the camera to normal. This procedure is reversible (i.e. not a permanent modification), and takes only a few minutes to do). The second step involves setting the camera's exposure control all the way to the "darken" setting whenever taking photos. Using the camera in this manner will give correct exposures except in very bright sunlight, which may cause the photos to still be slightly overexposed. You must be aware, also, that the camera resets the exposure control every time the camera is opened, so one must be mindful to set the camera all the way to "darken" every time the camera is opened. Furthermore, the exposure cannot be darkened if it is too bright, since the camera is already set all the way to the "darken" setting. This method has the advantage of providing much faster exposures (allowing photographs to be taken in dim lighting conditions without flash), and also does not degrade the image quality with a filter in the lightpath.
Method 4 - Electronically modified cameras:
This is by far the best type way to use 600 film in an SX-70. The SX-70 camera can have it's circuits modified so that it correctly exposes 600 film normally, and can have it's film chamber modified so that a 600 pack fits without trimming off the tabs. The advantage to this type of camera is that it will expose the film correctly without the use of filters, and the 600 cartridge will fit without having to trim off the tabs. Full exposure control is retained, and one does not have to worry about forgetting to set the exposure to "darken" each time the camera is opened. Furthermore, this type of modification allows the camera to benefit from faster exposures, as it causes the camera to function at a true ISO 640 film speed. These modifications are very difficult to perform except by experienced camera technicians, and are beyond the scope of this article. However, there is a west coast camera technicial who offers the modifications.