Tuesday, September 15, 2009

Which Medium Film Format?

photographyIn this article I'll expand a bit on medium format cameras, based on the process I went through figuring out what was best for me. I trust this will be the right approach for others considering the plunge. Sometimes the experts can be so confusing! (Though by all means read them as well. There is a world of information out there at the end of a search.)

First things first: What is medium format? It seems to be defined by exclusion: medium format is larger than 35mm and smaller than large format. Today the only practical readily available film for medium format is 120, so I'll limit my discussion to cameras that support 120 film, even if there are a multitude of other historical options.

In my last article I tabulated film/sensor sizes following the dictum "bigger is better". In the following table I expand on the options, starting with the smallest professional option and moving up through the medium formats. I have omitted the point and shoot cameras I previously included. Before someone argues that the "cropped sensor" APS-C sensor is not professional, let me say that magazine and stock agencies disagree. You can print a full magazine spread from this sensor with no compromise in quality, so that's professional enough for me. And before someone argues that a professional photographer can use any camera and get a good shot I'll say "sometimes, but not consistently... and a pro needs to be consistent."

OK, enough with the provisos. This table shows the camera format followed by sensor/film size and ratio. The fourth column is the calculated diagonal size of the sensor, which also indicates the "normal" lens size. Yes, Virginia, normal on 35mm is not 50mm but 43mm. I know there's a whole whack (a size measure larger than a gross but smaller than a gazillion) of 50mm lenses out there, but they are all "wrong". (Only Pentax made a 43mm lens and you should try it sometime.)


format.. image (mm).. ratio.. diag (mm).. factor
6x9..... 56×84....... 3:2.... 101........ 3.6
6x7..... 56×70....... 5:4.... 91.2....... 3.2
6x6..... 56×56....... 1:1.... 79.2....... 2.8
645..... 56×42....... 4:3.... 69.7....... 2.5
35mm.... 36×24....... 3:2.... 43.3....... 1.5
APS-C... 23.6×15.7... 3:2.... 28.3....... 1.0


The final column is a quality factor based on the smallest size here, APS-C. Read the last article for why a larger sensor is "better".

OK, so who makes these medium format cameras? More to the point, who once made them for film, given that we cannot afford the current-day digital versions?

In order to make the discussion shorter I'll look only at SLRs. A single-lens reflex has a mirror assembly that allows you to see through the viewfinder exactly what the film sees. Most of us are used to this from digital cameras. To give up the accuracy and convenience of an SLR is not something I want to do at this point. I want interchangeable lenses, and I want to be able to change these with a roll of film in the camera.

I note in passing that one can get into medium format for less money by opting for a TLR (twin lens reflex), which uses one lens for the viewfinder and a second for the film. Do check these out if you are on a very restricted budget, but note that many older units will need a CLA (clean, lubricate, adjust) to bring them up to speed.

Looking at the sizes, largest to smallest:

If we want a 6x9 camera I think the only real option is a Fuji rangefinder.

The 6x7 format includes the Mamiya RZ/RB 67, Pentax 67 and Bronica GS-1. All of these are quite large and loud. The Pentax has serious mirror slap issues. This size is impractical to me. If I want a bigger camera I prefer one in which the film or lens planes can be adjusted, but that is another article for another time. For me, 6x7 falls between two stools.

6x6 is the classic square format made famous by Hasselblad with such models as the 500C and EL. Other cameras to consider include the Rolleiflex SL66, Bronica SQ, Kowa 6/Super 66, Exakta 66, Kiev 60, Pentacon 6, Rollei 6008 and Kiev 88 (the last two of which also do 645). I did not want to chance the workmanship of the Russian designs, which is rather hit and miss. That might be fine if you know what you are doing, but as a beginner I might find it more difficult to separate my mistakes from errors in my gear. On the other hand, the better models here are quite expensive, especially if one wants additional lenses. But certainly 6x6 is a great format to explore, especially if one is partial to the square format.

645 cameras include the Mamiya 645, Contax 645, Bronica ETRS/ETRSi and Pentax 645. Of these, the Pentax is the least expensive system and has first-class lenses. While the original model was rather klutzy and feature-poor, the 645N has just about everything one would want in an SLR, including auto-focus, three metering modes, motor advance, easy film handling, DOF preview, multiple exposure, a nice viewfinder and great interface. Due to precise registration, 16 shots (not 15) may be had from a roll of 120. It has interchangeable viewfinders and accessories like an eyepiece and right-angle finder.

What the 645N lacks is flash sync at any speed faster then 1/30s, unless one gets one of the two available leaf shutter lenses. But using flash is not important to me. It also lacks mirror lock-up (MLU) but it does not need it, as the vibration from the mirror moving is minimal (this has been tested).

Another disadvantage is that the film backs cannot be exchanged mid-roll. They exist for ease of loading, not for flexibility. That's a shame, but is one of the things that keeps the size and weight reasonable.

Two cool features. Pentax 645 lenses (and indeed Pentax 6x7) can be used on K-mount cameras with simple adapters. This can save thousands in lens costs if you work with multiple systems.

The film is imprinted with all the shooting data, so one is freed from having to take detailed notes. This is a great learning tool and was a big reason I chose this system.

You may find a different system to your liking. But in any case you will be reaping the rewards of medium format.

My series will continue as I investigate film and developing.

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6 comments:

shel said...

I have a k2000, haven't shot film in awhile, but also pondering experimenting with film. I decided I'm going the 35mm route, since I can pick up a second hand 35mm camera cheaper, and since pentax 35mm is compatible with some of my pentax lenses, and since 35mm film and developing/scanning/printing is cheaper and more readily available than it is for 120 film.

My assumption is the 10 megapixel K2000 is superior in every way to standard 35mm film, but that film might give some creative advantages since it forces you to slow down, and think about what your shooting. I'll find out next week, when the camera I bought on EBay arrives.

I would compare format by the area of the negative, not the linear enlargement, so APS digital to FF digital would be 2.25x which is 1.5x squared. And 645 compared to 35mm would be 2.7x and 6x7 compared to 35mm would be 4.5x, and the APS digitial to 645 multipler would be 6.3

But the focal length is linear, so use the square root of the area multiplier. So a 28mm F/2.8 lens for APS digital is analogous to a 42mm F/4.2 lens on 35mm film, and a 70mm F/7.0 lens for 645. All three would have the same DOF characteristics, if enlarged to the same area.

robin said...

Thanks for the detailed comment. I look forward to hearing from you as your adventure to 35mm continues. I too thought that digital is likely the equal of that format which is why I decided to leapfrog it to 645. But each format offers its own advantages.

As for comparing formats, there is certainly some debate. Your comments anticipate my next post, so I'll leave discussion until then.

shel said...

After "which format" you need to decide which type of film. For my first roll, I'm leaning towards Kodak Ektra, which is C41 negative film, maybe the kodak B&W C41 film. And then have it scanned/printed at Costco at 6 megapixels. I'm looking forward to trying the 28mm F/2.8, which is wide angle with selective dof, which is the only fov/dof combination that I think APSC digital can't reproduce. But first, I need to wait for the camera to arrive.

Any progress on which camera/lenses you're getting.?

robin said...

I now have a Pentax 645N with 75mm and 150mm lenses. I also have decided on a couple of film stocks, which I will likely blog about as I get time.

Right now I am putting together darkroom gear. That I will surely write about!

Yuri H said...

The 645 series has a flash sync of 1/60 not 1/30. Perhaps you were thinking of the 6x7, which has a flash sync speed of 1/30.

Anonymous said...

The Bronica GS-1 is a strange camera, because it has film backs for 6x6, 6x7, 6x4.5, 6x2.4(35mm) and normal 35mm. The medium format back are for 120 and 220 type film. There are also different matglasses for the different film types!

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