The Polaroid Folding SX-70 on Steroids: A Review of MiNT Camera’s SLR670-S

The MiNT SLR670-S (right) and the original Polaroid Alpha 1 (left)

One of the frustrations of working with the Polaroid SX-70 camera is its fully automatic exposure system. As a well-seasoned photographer, I am accustomed to being in full control of setting aperture f-stops and shutter speeds to determine the correct exposure for my pictures. For Polaroid cameras—including the sophisticated folding SX-70 camera of the 1970s and 80s—the sole user control is the uncalibrated exposure compensation dial allowing the exposure to be adjusted lighter or darker by some unknown factor. Getting a good photo on the first try is unlikely and, on occasion, I have used an entire film pack to get one decently exposed image.

There is but one way to gain some semblance of exposure control on an SX-70 camera and that is to buy a specially modified version.

Enter MiNT Camera, a Hong Kong-based company that refurbishes vintage folding SX-70 cameras, installs new electronics and a new electric eye, reclads the camera with black or brown leather and adds a small exposure control module—something they call the Time Machine—that attaches to the camera’s flash socket. MiNT produces three versions of its camera: the SLR670m has the Time Machine, works with SX-70 and 600 films manually and with SX-70 in Auto mode or with the Time Machine detached; the SLR670-S adds an Auto mode for 600 film and the camera natively shoots Polaroid 600 film with the Time Machine detached; the SLR670-X adds external flash sync and metal cladding instead of the regular leather cladding. There is also a SLR670-S Classic model but it appears to use a pre-Alpha 1 version of the SX-70 camera and does not have a tripod socket—which I consider essential—or neck strap loops.

My comments below are based on my own SLR670-S camera. The camera was purchased with my own money (this is not an inexpensive camera) and my comments are not sponsored or paid for by MiNT Camera.

A video version of my SLR670-s review.

The new electronics allow the camera to natively use Polaroid 600 film with an ISO film speed of 640. That’s a whopping 2.5 f-stops faster than the ISO 100 SX-70 film the cameras were designed to use. 

That’s incredibly helpful, but MiNT’s Time Machine is the real game-changer. Aside from its Auto modes for both the SX-70 and 600 films, it offers manual shutter speeds ranging from 1/2000 down to ½ second as well as Bulb and Time modes for long exposures. There is also an “off” position that disables the shutter release and shuts down the entire camera.

The Time Machine can be detached from the camera. As mentioned, it slots into the original flash socket on the camera. Removed, the camera functions much as it did originally—fully automatic with exposure compensation via the camera’s quirky lighten/darken dial—except it is tuned to use 600 film exclusively. Note that the Time Machine needs to be removed in order to attach a flash, such as MiNT’s Flash Bar 2.

A worrisome side-effect of attaching the Time Machine via the camera’s flash socket is that it is not a secure connection. If you use a strap to hang the camera around your neck, the Time Machine hangs down and is prone to fall off as you walk. I say this from experience: on my first winter walk with the SLR670-S and Time Machine hanging from a neck strap under my parka, I pulled the camera out for a photo and was unpleasantly surprised to find the Time Machine missing. After a panicked retracing of my steps for about 500 metres, I found my precious camera bit laying in the snow. Lesson learned. I now carry the Time Machine in a pocket if I’m using a neck strap and only attach it when taking a picture. 

The SX-70 folding camera is widely believed to have a fixed f/8 aperture and MiNT reinforces that assumption in its instructions. Basically, you set your exposure meter to the appropriate film speed, take a meter reading and then use the correct shutter speed for an f/8 aperture. In fact, the camera’s original aperture also functions as the shutter and as the shutter/aperture opens, it goes from f/96 to f/8 and then closes from f/8 through f/96. How long the aperture stays open at f/8 during a 1/60 second exposure (for example) is a matter of mind-boggling complexity devised by the engineers at Polaroid Corporation in the 1960s and 70s. If you want to dive deeper into this optical magic, here’s an article on the Open-SX website: https://opensx70.com/posts/2018/11/sx70-shutter.

The significance of this is that setting a reliable exposure on the SLR670-S depends on a known aperture setting. From my tests, f/8 seems to work. That’s a very “slow” aperture so most shots are going to be at f/8. However, I do wonder if very bright scenes are actually shot at a smaller aperture, which could result in a false meter reading. I haven’t noticed this when shooting bright sunlit snow scenes. Perhaps my concerns are a tempest in a teapot.

There is downside to this aperture-priority exposure control method, where the camera f-stop is fixed at f/8 and the user adjusts the shutter speed: shutter speeds are only adjustable in what is equivalent to a full f-stop interval. That’s a pretty crude jump in exposure, especially considering the limited latitude of current SX-70 films. If a photo comes out a bit too light, adjusting the shutter speed from (say) 1/125 second to 1/250 is likely to result in a photo that is too dark. If there was an adjustable aperture in the lens—as is the case with most DSLR/SLRs and even many point-and-shoot cameras—that aperture is typically adjustable in half-stop intervals, allowing for a finer exposure adjustment. 

This is not the fault of MiNT Camera. They are stuck with the optics Polaroid created. To add a variable aperture, thus allowing full manual control, would likely require the gutting of the SX-70’s lens board and replacing it with something entirely new, an expensive proposition.

Shutter speeds are notorious for their inaccuracy. For example, a 1/125 second shutter speed may actually be 1/00 or 1/150 second. This may not seem like a big thing but, in concert with the limited latitude of Polaroid film and a film speed that can vary by ± ⅓ stop (as stated on Polaroid’s film packaging), small inaccuracies can have a huge impact.

It is hard to tell how accurate the Time Machine shutter speeds are. In doing my own tests in an attempt to use the Zone System to determine exposure times (look forward to this in a future post), the shutter speeds seem to perform as advertised…with the exception of the 1/60 second setting which, on my camera, appears to be off by a full f-stop. That’s not good. It means I need to avoid this shutter speed, which could be problem in some situations given the fixed f/8 aperture. 

When I received my new SLR670-S MiNT Camera last December, I had a problem with the camera: when I pressed the shutter button, the camera would click and do nothing. Or it would click and, many seconds later, expose the film and eject it. Or, in rare instances, the camera worked as it should. I emailed MiNT Camera about my problem and they responded the same day. The camera was returned to them for servicing (they agreed to reimburse the shipping cost with an equivalent amount of film) and MiNT quickly repaired the camera, shipping the repaired camera back to me. I found their service to be efficient and friendly. The cameras also come with a 3-year warranty. This is certainly a commendable level of support.

However, be mindful that MiNT Camera is located in Hong Kong. That’s a long way from my Winnipeg studio. Even with expedited shipping in both directions, the whole process took a little over five weeks, most of which was transit time.  

You need to be a keen SX-70 photographer to justify the steep CAN $1239 list price for the SLR670-S, although MiNT occasionally runs sales on it cameras. One possible rationalization for laying down this much money is the amount of expensive SX-70 film saved by pinning down a good exposure in one shot. My own rationalization is a matter of creative control: while on a walk, I can take a picture and maybe one more at a higher or lower shutter speed, put the photos in my pocket, continue on my walk and be reasonably confident that I will have a beautiful, well-exposed SX-70 photo print at the end of the day. That, my friends, is well worth the price of admission.

Does the camera have shortcomings? That the Time Machine falls off the camera is a small irritant. And I wish there was control over aperture settings but that is a problem baked into the original camera design, not MiNT’s modifications. The inaccurate 1/60 second shutter speed is my biggest concern. But I am so enjoying my SLR670-S that I am unwilling to part with it for the five-plus weeks it will take for the repair—if it is repairable. Instead I will curse the sun when it forces me to use 1/60. Damn you, sun!

Edwin Land and his team at Polaroid created a brilliantly designed camera in 1972. Imagine a camera that takes images larger than those made with a heavy, bulky Hasselblad medium format camera of the same period yet, magically, folds down into a compact pocketable package! MiNT Camera has built on that innovation, making the folding SX-70 camera into a formidable creative tool. Simply put, the SLR670 is the best instant photo camera on the market today.  

Resources:

MiNT Camera: https://mint-camera.com/en/

MiNT Cameras are also available through B&H Photo: https://www.bhphotovideo.com

If you live in Canada and would like to buy a refurbished, vintage SX-70 camera, try Toronto Polaroid: https://www.torontopolaroid.ca 

If you are interested in viewing or purchasing (even better!) my From Our Windows book, which consists of Polaroids taken with my first SX-70 folding camera, visit my website: https://www.firmangallery.com 

4 thoughts on “The Polaroid Folding SX-70 on Steroids: A Review of MiNT Camera’s SLR670-S

  1. Salvatore Rotondo July 4, 2021 / 3:43 am

    Thank you for the written article as well as for the YouTube review of the Mint cameras; the reviews are thorough and informative.

    Have you had strobe sync issues with the Mint SLR670s? I hooked up an external strobe and the image was about two stops underexposed. If you can share any insight on this, I would greatly appreciate it.

    Thank you very much.

    Sal

    Like

    • David Firman July 5, 2021 / 11:42 pm

      Hi Salvatore,
      Thanks for your kind comments. I don’t use flash much and haven’t tried it with my SLR670s so I’m afraid I have no useful advice to offer. Are you using the S model or the 670-X? The 670s does not have an external flash sync plug built into the time machine. My understanding is that you need to get the 670-X which has a plug in for an external flash. I think you could attach a Mint Flash 2 to the 670s, which does have an external flash plug in. But you would need to remove the Time Machine to attach the flash, in which case exposures revert back to the automatic exposure control of the camera and exposure adjustment is limited to the camera’s lighten/darken wheel.
      Cheers, David.

      Like

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