A very brief history of camera design – film sizes, mirrors, manual focus aides, and mirrorless

Written by Gary on July 5th, 2015

There are a lot of people taking up photography who are really only aware of the digital age and thus I thought it was opportune to bring them rapidly up to speed on why we have cameras they way we do and thus what the future may hold.

So let’s go back to the 19th century when film based cameras were first being developed – the initial ones are like those seen in Western movies – mounted on a tripod, while the photographer buries himself under a black cloth behind the camera and uses some kind of primitive flash to light the portrait. What was he doing under the black cloth?

These cameras used photographic plates which could be moved out of the back of the camera and replaced with large ground glass screen which would enable him to focus the image – as long as he could make it dark enough to see the faint image. Once the subject was focused, he would remove the glass plate and insert the film plate, and then he could take the shot. Given that the film speed in those days was so “slow” – perhaps ISO 4 or so, and the lenses needed to be used at f/22 or so for the large format film plate, the exposures would be too long without additional light.

Obviously, the above system was not conducive to the take up by consumers – it was a very technical and slow photographic process.

The Kodak Brownie

George Eastman started manufacturing paper film in 1885 then celluloid in 1889 and created his 1st simple camera, The Kodak, in 1888 with a fixed aperture, focus and shutter speed and a single roll of film that the camera needed to be sent back to the factory for processing – not a great option for the masses.

In 1900, Eastman Kodak needed to sell more film so produced the affordable ($1) and quite simple even for children (“you press the button, we do the rest”) revolutionary Kodak Brownie – a simple box which used a roll film of type 117 producing 6cmx6cm square images (what we call “medium format”). It had no viewfinder or focus mechanism, just V sighting lines on the top or an optional add on viewfinder and thus was designed to create the “snapshot”. Only the film roll needed to be sent for processing.

The Brownie series of cameras were popular for children and families into the 1960’s.

6×6 “medium format” film cameras

The Brownie created a large market for 6×6 film and this spurred manufacture of a whole industry of more professional and enthusiast cameras based upon 6×6 film types (including the very popular 120 film).

These camera manufacturers had to solve a few issues though:

  • how can the photographer compose the image?
  • how can the photographer accurately set a focus for the subject?
  • how can the photographer adjust exposure for different light intensities?

Adjusting exposure was a relatively easy technical problem to solve – add an adjustable iris diaphragm in the lens, and an adjustable spring operated shutter within the lens.

Setting focus and composition though was a different matter with various compromise solutions:

  • adding a reflex mirror which directed the view to the top of the camera allowing it to be viewed from above as a waist level finder, and then prior to exposure being made, the large mirror is removed out of the way so the light will hit the film when the shutter opens – this created heavy, big, noisy “SLR” Single Lens Reflex cameras which ideally had the mirror locked up well before the exposure to minimise camera shake and then had to be manually returned to view next image.
  • adding a 2nd synchronised viewing lens which moved in sync with the main lens during focus and usually a fixed mirror for this lens – this created a heavy, big, quiet “TLR” Twin Lens Reflex camera but what you see is not really what you get – there is parallax error for closer subjects which affects composition and requires correction mechanisms, useless for macro work, and you don’t get to see  effects of filters such as polarising filters. Nevertheless, the fact you didn’t need to lock up the mirror made these cameras extremely popular in the 1930’s (thanks to the more compact Rolleiflex in 1928) through to the early 1960’s for tourists and portrait photographers.
  • adding a small fixed viewing lens with a special mechanism to overlay images to show the photographer when the subject is in focus – the quiet, but large and relatively heavy rangefinder camera. This had similar issues to the TLR and in addition only worked with certain focal length lenses to match the rangefinder mechanism.

There was a need for smaller cameras – enter the 35mm “full frame” cameras

The movie industry had been using 70mm wide film for years, and from 1905 onwards various manufacturers were making cameras for 35mm cine roll film which was 70mm cine film cut in half long ways. These cameras started to gain popularity with Leica’s 1st camera in 1925 followed by a Contax in 1932.

But again it was Kodak who leveraged this popularity by creating a much easier to use 135 cartridge film in 1934 and a Kodak Retina I camera to use it with. In the late 1930’s the Japanese manufacturers started to create 135-type cameras. In the 1950’s Asahi Pentax had developed the instant returning reflex mirror which further increased the usability and popularity of the SLR.

Street photography became easier thanks to 35mm rangefinder cameras such as those made by Leica, and later, a multitude of Japanese versions were sold to families in the 1960’s.

Meanwhile professional photojournalists started giving up their large medium format rangefinders for more versatile, compact 35mm SLRs of the 1960’s.

In the 1960’s, Olympus created an even smaller Olympus PEN rangefinder system using half a 35mm frame as the image size – hence called “half frame” cameras.

In 1963, Kodak introduced their 126 instamatic square film cartridges to make loading film even simpler and easy for children to do, spurning a new generation of children taking snapshots.

The 1970’s saw an explosion in the popularity of the 35mm film SLR helped along by Olympus who further re-defined the product by creating their beautiful, compact, quieter OM system with off-the-film TTL flash metering.

Professional wedding and fashion photographers needing to create large prints were generally not comfortable with the large print quality from 35mm film and still used medium format SLRs, while landscape photographers used even larger film cameras such as 6cmx17cm image panoramic cameras.

In the late 1980’s, Canon changed the SLR world, taking an enormous risk in abandoning its popular manual focus FD lens mount system of cameras and lenses, and thereby making them redundant and practically worthless – not great for your fan base, and created a new autofocus SLR system – their EOS system with electronic focus (EF) lenses which were  to dominate the photojournalist, nature and sports professional photographer world for the next two decades while Nikon played catch up and Olympus lost their way, never really creating an autofocus film SLR system.

How did the photographer accurately focus these cameras without autofocus?

Autofocus was not mainstream in cameras until the mid to late 1980’s, yet generations of photographers have always been able to get well focused images, even of fast moving sports – how did they do this?

Part of the reason is that they didn’t have to have accurate focus – the lenses of the day for 35mm cameras were generally sharpest at f/8 hence the adage “f/8 and be there”. If you are shooting at f/8 you do have a reasonable amount of depth of field to play with, so one option is to preset the focus for your subject’s estimated distance – indeed, this is the only way you could do it on most instamatic cameras – set for people or landscapes and depth of field will handle the rest. This technique is called zone focus and users looked at the depth of field scale on their lenses and worked out a good focus to achieve what they wanted.

But what if you wanted to use wider aperture lens with narrow depth of field, you really needed to get more accurate.

Enter the focusing screen.

The focusing screen is the ground glass used on all optical viewing devices including on dSLRs made today.

Before autofocus, most professional SLR cameras allowed one to remove the screen and replace it with another style depending upon your needs and lens being used.

Commonly, these screens used either a central split image (you align the images for focus) or a central microprism (stops shimmering when in focus) as well as the surrounding ground glass for the user to accurately ascertain focus. Unfortunately the split image, microprism and even the ground glass did not work with all lenses, so we had a screen for macro work, another for astro work, etc.

Most modern dSLRs with autofocus now have a fixed screen without split image or microprism aides, and which is optimised for f/2.8 apertures – if you are using a f/1.2 lens, the camera may automatically close the aperture to f/2.5 or so to optimise the view on the screen.

Modern dSLRs are NOT optimised for manual focus although they often do have “AF confirm” – pressing the AF button whilst turning the focus ring in manual focus, the AF confirm light comes on when it detects focus is achieved as determined by the AF mechanism – this requires a CPU chip in the camera lens or lens adapter.

The latest evolution – the mirrorless camera

Now that we are essentially in a digital camera world with cameras having digital sensors instead of film, and electronic viewfinders are now giving very acceptable views and with many possible functions not available to optical viewfinders, there was no longer a need to have a clunky, noisy reflex mirror which added to camera shake.

Enter the mirrorless camera.

The electronic viewfinders continually improve, and now give even larger apparent views than the best optical viewfinders, allow display of far dimmer subjects making it easy to compose on star fields or with extremely dark filters in place such as infrared filters or 10x Big Stopper ND400 filters.

Not only that, they give you real time live histograms, highlight/shadow warnings, compositional grids, real time pre-visualisation of creative picture tonalities or colours, keystoning adjustments or even exposures.

Furthermore, unlike with dSLRs you still can hold the camera to your face for steady camera holding when using Live View such as in video mode, and there is no need to microadjust the AF system for each lens as is the case with dSLRs.

But wait there’s more – you now gain some awesome manual focus aids such as:

  • image stabilised magnified view
  • focus peaking
  • live boost II so you can see really dim subjects such as faint stars

By removing the mirror, the sensor to lens distance can be shortened and thus allow radical new designs of lenses, especially wide angle lenses, and the ability to mount almost any other legacy lens and still attain infinity focus.

And, just as in the days where there was a market for highest quality large heavy cameras and a market for smaller, compact, quieter, versatile take anywhere cameras, these markets are still with us today and thus enthusiasts and professionals can choose from:

  • high resolution, potentially very shallow depth of field full frame image stabilised mirrorless camera such as the newly announced Sony A7R II which has been optimised to autofocus Canon EF lenses
  • compact, light, versatile, high image quality Micro Four Thirds cameras such as the Olympus OM-D family

Why Micro Four Thirds?

  • sensor size is small enough to allow relatively compact, light lenses with excellent edge-to-edge image quality – usually with much sharper edges than full frame lenses
  • sensor size is big enough to allow just the perfect amount of shallow depth of field for your portraiture when using the premium f/1.8 lenses
  • sensor size is big enough to give a good compromise of resolution vs high ISO noise performance – currently 16mp to ISO 3200, although this will further improve as technology improves
  • large range of lenses optimised for sensor size and silent, fast, more accurate autofocus – even AF on the closest eye
  • ability to use almost any lens ever made and have them image stabilised
  • ability to use full frame lenses with focal reducer adapters or tilt-shift adapters
  • optical image quality deteriorates exponentially the further from the centre and thus smaller sensor lens makers will always have the advantage in lens design
  • 99% of users do not print sizes greater than 20″x30″ and Micro Four Thirds can print to this size acceptably well
  • higher resolutions are possible by panoramic stitching or by sensor-shift technologies such as the Olympus 40mp mode which will be further improved to be usable hand held

And this is the dilemma faced by Canon and Nikon who are yet to really invest in mirrorless systems (not including the small 1″ sensor of the Nikon 1 system or the rather pathetic EOS-M system).

PS. Don’t get me wrong, the current Canon and Nikon systems are wonderful, albeit heavy and expensive, and I have well over $20,000 worth of Canon pro gear, and although they probably will still be around in 10-15 years,  I don’t believe that needs to be the way of the future for MOST people, and I far prefer to carry my compact Olympus gear which does not break my back, packs into cabin luggage on airplanes easily,  and is more affordable and fun to use, and it gives me just as good photos, if not better.


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