Zeiss Ikon Ikonta 35

This is a folding camera from Zeiss Ikon based on the medium format Ikonta series. This camera gave rise to two lines of cameras in the mid-50s - the Contina and the Contessa cameras. I have two of these,  an early Ikonta 35 late 1940s to very early 1950s and a slightly updated version.  First I am going to describe the early/original version and then briefly the changes on the updated version.

Ikonta 35 ready for use

lens: Novar

focal length:  45 mm

apertures: f/3.5 to f/22

focus range: 0.8 m to infinity

lens fitting: fixed

shutter: Prontor S

speeds: 1, 1/2, 1/5, 1/10, 1/25, 1/50, 1/100, 1/300

flash: PC connector

film size: 35 mm

It measures 120 mm by 75 mm by 40 mm (closed), 80 mm (open) and weighs 440 g.

Ikonta 35 with its carry case

The lens door opens downwards which leaves plenty of room at the sides for the fingers of both hands. On my Ikonta 520 (120 film camera) - and my Nettar folders - the lens door is released by pressing a button on the top and the lens door snaps open on springs and pulls the lens forward to its operating position. On this camera, you slide a button on the top of the lens door and pull the door down by hand. When the door is fully open you have to give it a firm press to click it into place.

Ikonta 35 - folded

The lens is a Novar made by Rodenstock, which is a triplet.  During WWII, bombing of Dresden destroyed Carl Zeiss's lens factory and after German partition West German Zeiss set up new lens making facilities in Oberkochen. It was a long time before they could make enough lenses and so used lenses by Rodenstock and Schneider. Novar lenses are usual excellent if stopped down to f/8 or so - which is what I generally do for all lenses - so I am expecting this lens to be a good performer. Its maximum aperture is f/3.5 which is not spectacular  but plenty wide enough for most practical purposes. The focal length is 4.5 cm - this dates the lens as usual practice in the first half of the 20th century was to quote focal length in cm and in the second half of the 20th century to quote in mm - so, the last of pre-war stock or very early post-war production. The serial number of the camera is followed by an asterisk which I am told probably means the camera was partially made from pre-WWII components so I expect the lens is a pre-WWII lens - the last of Zeiss Ikon's stock? 45 mm is 'normal' for 35 mm film so this lens will render scenes much as human eyes see them.

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Blog copyright by John Margetts, 2014
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Ikonta 35 - right hand view

The shutter is a Prontor S - pre-war Zeiss Ikon used their own Klio name for Prontor II and Prontor S shutters - they seem to have abandoned this after the war.  The S signifies the shutter is synchronised for flash but there is no means of selecting between X or M synch (this was introduced on later Prontor S shutters  - see below - and was standard on the Prontor SV and Prontor SVS shutters). At this age, the shutter needs to be cocked by hand. This is different on this camera to any other shutter that I have come across. You pull the cocking lever anti-clockwise and the lever pulls a second lever across - the first level returning to its rest position.

Ikonta 35 - left hand view

The Prontor S shutter has a top speed or 1/300 which I generally find to be fast enough. My usual films are either 100 ISO or 200 ISO and this allows me to use f/8 or f/11 in good light year round. The shutter has a self-timer (Vorlaufwerk) which we are always told not to use on old cameras. On this camera, the self-timer is very hesitant and took over a minute to fire the shutter - design time is eight seconds! As is usual with old cameras, the slow shutter speeds are way off and unusable - 1/5 seconds is about 5 seconds. On the other hand, I use these old cameras hand-held and so my longest exposure will be 1/50. the slow speeds and fast speeds use different mechanisms within the shutter - 1/50, 1/100 and 1/300 are in the right general area, judging by ear and I shall be surprised if they are not usable. Half a stop either way is well within the latitude of film.

The shutter release is a strange affair. It is not the lever provided by the shutter makers, nor is it a body release. It is a secondary lever attached to the shutter barrel at the top. It is marginally better than the primary release but not as good as the body releases that Zeiss Ikon were using in the late 1930s. Actually, it is very similar in position and action to the shutter release on the Tenax I of 1939 (both cameras designed by Hubert Nerwin). There is also the ubiquitous cable release socket.

The adjuster for the aperture is non-standard as well. It is a toothed wheel on the left side of the shutter housing which is not obvious without the manual (I do not have the manual) and took me a few moments to work out.

Ikonta 35 - top plate

The top plate is very uncluttered. In the centre is a raised part housing the (very small) viewfinder. It measures 9 mm by  6 mm (the same as on my Voigtlander 35mm folders of the same date) and is the weakest part of the camera. This is a reverse Galilean finder ('reverse' because it is like looking through a telescope from the wrong end giving a reduced size view).

On the left-hand end is a reminder for film type - daylight colour, artificial light colour and monochrome. On the right-hand end is a tripod boss. This is the only time I have seen a tripod boss on the top of a camera and means that the camera would be upside down when fitted to a tripod. It would be just about possible to fire the shutter with the release lever but I suspect that anyone who put this camera on a tripod would have used a cable release. The MK II Ikonta 35 had the tripod boss on the lens door - a very big improvement! At either end of the top plate is a rectangular strap lug.

Ikonta 35 - bottom plate

The bottom plate has the film advance on left-hand end - this  is a knob. On the right-hand end is the rewind knob and in the centre of the base plate is a frame counter. In the centre of the film advance knob is a button to allow the take-up spool to turn backwards for rewinding the film.

Ikonta 35 in use.

I have run a roll of film through this camera now.  It is a nice camera to use (I know 'nice' is not a good word to use here) with no design problems getting in the way.  Using it is very similar to using a folding Voigtlander Vito camera.  The shutter release falls naturally (for a right-handed person) under the index finger of the right hand and the ring finger on the left hand can easily turn the film advance.

My main problem with using this camera was, as with all cameras of this age, the small viewfinder. I have developed a technique now of deciding the framing of the picture without looking through the viewfinder, taking my glasses off and positioning dominant parts of the picture without the view being in focus.  This actually works quite well.

The camera has a fault with the film advance mechanism - possibly two related faults. Sometimes when I try to advance the film, the advance knob will not turn. To get this to turn, I have to put my thumb over the lens (to prevent any light getting in), cock the shutter and release it a second time.  This was necessary four times in a 24 exposure roll of film. This suggests that the double exposure prevention mechanism fails to release the film advance on the first firing of the shutter. The second fault is that sometimes the film will advance two frames instead of stopping at one frame - this happened a couple of times wasting two frames. Apart from these two intermittent faults the camera behaved perfectly. There are no light leaks either from the back or from the bellows, exposure is fine as is focus.

New improved version.

Before sharing the results of the test film, I am going to briefly discuss the changes made between the original design as described above and the next version.

There are a couple of minor changes between the original version and the next version. The most obvious is the addition of an accessory shoe above the viewfinder, on the top plate. This is a 'cold shoe'  - there are no electrical contacts for a flash gun yet.

The other change is the use of a more modern Prontor S shutter. On the original Ikonta 35, the Prontor S shutter was synched for flash but there was no means of selecting the synch delay. There was also a self-timer lever. This updated version of the Ikonta 35 has an improved Prontor S that offers either X, M or F flash synch. For X synch you set the selector lever to X (or red) - the flash will fire as soon as the shutter is open. For M or F synch, it is more complicated. First, you set the flash synch selector to yellow. This will give you synch for F flash bulbs (the flash is fired 5 milliseconds before the shutter is fully open to allow the brightness to build up). For M synch, you set the flash synch selector to yellow and the self-timer to M which will fire the flash 20 milliseconds before the shutter is fully open, again to allow the brightness to build up. To use the self-timer actually as a self-timer, the flash synch selector must be set to X/red

There are also a couple of very minor changes - the shutter assembly no longer has a cable release socket so Zeiss Ikon has added one at the top on the other side to the shutter release lever. The release lever is now about twice the diameter of the original one. The last change is that the focal length of the lens is now quoted as 45 mm rather than 4.5 cm.

There are also changes to the leather case. It is now an every ready type case which has a secondary film advance on the underside that meshes with the film advance on the camera. this means the camera can now be used without removing it from its case. There is also a tripod boss on the underside of the case which means it is no longer necessary to have the camera upside-down to attach it to a tripod.

The photographs ( from the original version):

St John the Baptist, Lincoln

Orthodox church, Lincoln

St Mary's Church, Frampton, Lincolnshire

St Peter & St Paul, Kirton, Lincolnshire

St Peter & St Paul, Kirton

St Peter & St Paul, Kirton

St John the Baptist, Lincoln

St Mary le Wigford, Lincoln

St Benedict, Lincoln

St Benedict, Lincoln

St Mary's, Frampton

Gravestone, St Mary's, Frampton

St Mary's

St Mary's

St Peter & St Paul, Kirton

Balda Baldina

This is a very nice folding camera from 1930s Germany.  It is one of the first cameras to use Kodak's 35 film cassette - this was made soon after Leitz made the Leica (1925) and Zeiss Ikon the Contax (1932).  It follows Kodak's lead in producing a folding camera unlike Leitz and Zeiss Ikon who both made rigid 35mm cameras.  The camera is fairly small - it measures 120mm x 82mm x 35mm when closed and 120mm x 82mm x 85mm when open.  It is almost exactly the same size as Voigtlander's later Vito and Vito II cameras but a bit heavier. The covering seems to be leather rather than leatherette.  This is my second Balda camera - the other being a Baldessa from 1965.

lens: Schneider Radionar
focal length: 5 cm
apertures: 3.5, 4.5, 5.6, 8, 11, 16
focus range: 1 metre to infinity
lens fitting: fixed
shutter: compur leaf
speeds: 1, 1/2, 1/5, 1/10, 1/25, 1/50, 1/100, 1/300
flash: no connector
film size: 35mm

Balda Baldina - front view

This camera had been stored somewhere not particularly dry before I bought it and the finish showed the results. The leather was very dry and dull, much of the nickel-plated steel has rusted and the moving parts were all very stiff.  I attacked the leather with Bestbeloved's leather restorer and it is now a bit more subtle and has a nice sheen. Moving parts have had a drop of oil/naphtha mix (I mix 2 parts clock oil with one part naphtha to produce a freely running oil. This flows into hinges and axles easily - and when the naphtha evaporates the part is left with a very small amount of oil) and now move easily. I have yet to deal with the rust but will do so when I have finished the test film. I shall rub down just the rust and then treat it with Loctite Rust Remedy. This leaves a durable black finish which I shall leave as-is. The last thing to note, condition wise, is the presence of 'Zeiss Bumps'. Zeiss Ikon cameras are notorious for these and this is the first time I have seen them on a non-Zeiss Ikon camera. they are caused by the manufacturer using a different material for rivets than he used for the body. A chemical reaction will then be set up in the presence of damp resulting in the build-up of corrosion products between the metal of the body and the leather covering. These 'Zeiss Bumps' occur on the lens door and in the leather by the take-up spool.

Zeiss Ikon and Voigtlander used die-cast aluminium for their camera bodies which made for strength and lightness with the added advantage that they were corrosion resistant.  This camera seems to be made from steel.

The outside is a mixture of leather and nickel plating and where the nickel has worn, the camera is rather rusty. My Zeiss Ikon Nettars from the same decade were leatherette and paint and where the paint has worn you can see the aluminium.

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Blog copyright by John Margetts, 2014
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top view

Balda's use of steel and nickel plating would have made the camera cheaper to make.  I assume that this also meant that the camera was cheaper to buy but it would not have been cheap. With a Compur shutter, it would have been aimed at a serious amateur photographer.

The camera is quite well appointed.  It has a 'proper' viewfinder rather than the metal frames that Zeiss Ikon's Nettars and Ikontas had.  This is small (as was usual even on expensive cameras) and is a reverse Galilean finder (that means it is like a telescope backwards as it makes things small). This viewfinder has a remarkable addition - a parallax adjuster. When you have set the focus on the lens, you put the same distance setting on the viewfinder and the viewfinder moves up or down accordingly. For infinity, the viewfinder is fully up and as you dial in nearer distances, the viewfinder lowers itself. Apart from this camera, I have only ever seen this on expensive rangefinder cameras.

On the top plate along with the viewfinder is the film rewind key and the frame counter. This last is beneath a hinged cover and counts from zero to 36.  This is a count-up counter, the user setting the counter to zero when loading a film into the camera.

Beside the viewfinder is a small button. Pressing this will release the hinged lens cover and the lens will spring forward automatically - it does so with a reassuring 'snap'.  The shutter leaves are between the lens elements so focusing is only front-cell focusing (i.e. only the front piece of glass moves when focusing, not the whole lens. This causes a slight degradation of the image with close-up work. For landscapes it makes not a jot of difference).

base view

The film advance is on the bottom of this camera - possibly to circumvent other manufacturer's patents, certainly not because it makes it easier to use. Advancing the film is not as straightforward as turning the knob (no lever advances at this early date).  Leitz, Kodak and Zeiss Ikon had 35 mm cameras on the market when this camera was designed and each had patented every aspect of camera design they could.  They also pursued patent infringement vigorously. The outcome of this is that manufacturers trying to bring new models to market had to find workarounds to avoid being sued. In this case, the film advance is locked until you press a button on the base of the camera. This must be released as soon as you start turning the film advance knob or you will advance more than one frame. To make this as hard as possible, you first have to push in the safety lever, then press the small button and then turn the advance knob.

Also on the bottom of the camera is a tripod boss.  This is the original 3/8 Whitworth thread rather than the more modern 1/4 Whitworth.  This is to one end of the camera - it seems to have taken camera manufacturers a long time to work out the point of balance of a camera.

Balda Baldina - folded

Inside is pretty much as you would expect even from a modern 35 mm camera - a sign that this layout was well designed from the start and not patented.

The hinged back has effective light baffles and so there is no need for foam light seals - nothing to go gooey and messy with age and nothing to start leaking light. In the centre of the back is the pressure plate to keep the film flat against the film gate. To one end is a nickel-plated spring to keep the film in place on the sprockets. Loading film is easy. There is a spring on the take-up spool under which the end of the film goes. No particular shape of film leader is required but the modern standard leader works fine.

When open, the door hinges on the left, leaving plenty of room for the right hand to have a firm hold. Many folding cameras hinge on the right leaving a restricted space for gripping.  Voigtlander's Perkeo and Vito cameras hinge on the right.

When holding the camera for use, the shutter cocking lever  must be moved upwards (this is a Compur shutter, a Gauthier shutter (Prontor) would need the lever moving downwards). The shutter release provided by Compur is hidden by the folding struts and cannot be reached. To overcome this, Balda have added an angled extension which can be reached by the middle finger of the right hand. There is also a socket for a standard cable release.

position of extension lever

Adjusting the shutter speed is easy - this is a rim-set shutter and you turn the outer ring until the required speed is aligned with the index mark. Altering the aperture is not so easy. The control is close to the door and between the folding struts. This is quite do-able but requires looking at the camera from the front.

I have finished the test film which raised a couple of things.  Firstly, firing the shutter. The extension lever that Balda have added to the Compur shutter release travels a long way before it fires the shutter. I found this rather awkward and difficult to hold the camera steady while doing so. Secondly, rewinding the film.  I have no instruction book for this camera and I have to work things out for myself. I assumed that the button that released the film advance mechanism would also release the rewind mechanism. Wrong! My attempt to rewind the film resulted in me pulling all the film out of the cassette. This meant a trip to Snappy Snaps to ask them to remove the film in their darkroom which they did. I now know that to rewind the film you have to lift the film advance knob and leave that other button alone. Oh well - this is all a part of the fun of collecting old cameras. Tomorrow, I shall collect the developed film and post a selection here.

OK. The test film is back - and none the worse for me trying to rewind it the wrong way - kudos to the staff at Snappy Snaps.  I am impressed with this camera. It was made in 1935 (plus or minus a month or two) and has worked flawlessly. The lens shows no sign of having been coated, which would have been very unusual in 1935, but is not particularly susceptible to flare. There is some flare visible in some of the pictures, but I have a habit of shooting into the light which would have been virtually unheard of in 1935 for the very reason that is causes flare.  The lens focuses well and produces high contrast colour pictures. The lens will have been colour-corrected to some extent as that is necessary for using panchromatic black-and-white film and the lens clearly has no problems with modern colour films.

There are marks on some of the negatives - basically, there are scratches which show up on the prints as black marks. I am putting this down to the damage caused when I attempted to rewind the film. It only affects a few of the negatives, most of them being fine.

The pictures:

Shooting to the south on a sunny day (that is, into the sun), hence the flare.

Shooting to the south again, but on a dull day - a small amount of flare.

Shooting to the north on a misty day. No flare but some mist visible in the upper parts of the picture.

Shooting to the south on a sunny morning - no flare as such.

Shooting to the east on a sunny day.

Shooting in a heavily shaded alley - good contrast and colours.

Emi K 35

Emi K 35

The Emi K 35 was made by the Oshiro Optical Works in Japan in 1956.  It is quite an attractive and well made little camera but basic in the facilities it offers.

lens:  Fujiyama Eminent Color

focal length:  50 mm

apertures: 2.8 to 16

focus range: 3 feet to infinity

lens fitting: fixed

shutter:  own make

speeds: 1/25, 1/50, 1/100, 1/300

flash: PC connector, X synch

film size: 35 mm

The camera is heavy, being made from die cast metal (presumably aluminium alloy) including the hinged back.  It measures 125 mm by 70 mm by 80 mm tall.  The main body is covered in black leatherette and the top and bottom plates are satin stainless steel.

The shutter release button is next to a raised part of the top plate and with my large hands it is a bit awkward to get my finger on it.  Film advance is by a lever.  In my camera, the spring that returns the film advance lever to its rest position is broken so it is necessary to put it back in place manually. However, the lever still advances the film and cocks the shutter, so this camera is quite usable.  

The viewfinder is small, but no smaller than Voigtlander were offering at the same time.  There are no frame lines in the viewfinder, so I assume the total image is what will be recorded on the film. On taking the camera apart to look at the broken film advance spring, I saw a square cut-out in the front of the top plate that is normally masked by the 'Emi K' logo on the front of the camera.  This suggests that a rangefinder was considered at some point in the design - either to be offered on another model or abandoned for this model.

One the left of the top plate is the film rewind which is a small crank (very small!) which is fairly difficult to use.  This crank pulls up to release the cassette for removal.  The only other thing on the top plate is an accessory shoe - a 'cold' shoe in flash terms.  For flash, there is a PC connector at the bottom of the shutter housing.

The lens is a Fujiyama Eminent Color lens.  There is a red 'C' on the lens bezel which I am sure indicates that the lens is coated (just about normal for 1956).  The whole shutter housing/lens assembly seems to be well designed and well made but feels a bit plasticky compared to Prontor shutters. Actually, the shutter housing is plastic which is not actually a bad thing so long as it is used thoughtfully.

The inside is as you would expect - a recess for the film cassette, machined guides for the film, a sprocket wheel to advance the film and a fixed take-up spool.  I am very much in favour of fixed take-up spools.  Zeiss Ikon and Ihagee both used removable spools and I spend too much of my time on my hands and knees retrieving the spool when using those cameras.  The camera back has the expected pressure plate (generously sized) and 'Zeiss bumps' in the leatherette.  'Zeiss bumps' are formed when the rivets holding components together react chemically with the metals used.  The back is aluminium alloy and I suspect the rWhitworthñ steel.

The base of the camera has a central tripod boss - 1/4 inch Whitworth.  There are no strap lugs on this camera - the manufacturers will have expected the user to use the 'ever-ready' case that will have been supplied with the camera.

Test photos

I was aware when I started that the return spring in the film advance lever was broken, but the mechanism itself seemed to work OK. As I used the camera it became apparent that the lever was not engaging with the internal mechanism properly and sometimes it took several sweeps to advance one frame.

Using this camera reminded me very much of using my Zeiss Ikon Contina Ic. They have a very similar size, shape and weight - I suspect Emi had the Contina in mind when designing the Emi K. Controls are minimal and are placed on the lens/shutter barrel. The viewfinder is nice and large and centrally placed. However, there are no bright lines for accurate composition.

The only problem I have had using this camera stems from the fact that the return spring  in the film advance lever is broken (as mentioned above). I initially thought that this would mean that I would have to return the lever by hand after winding on the film and otherwise all would be well. in fact, the film advance lever interacts with two sub-systems in the camera - the double exposure prevention mechanism and the missed frame prevention mechanism. Sometimes I would turn the film advance lever and nothing would happen, sometimes I could not turn it at all without pressing the shutter release a second time - this did not fire the shutter, it just freed the mechanism. I was never confident that the film was advancing properly. Although the rewind knob turned as I advanced the film - a sign that the film is moving - it did not turn smoothly. Looking at the prints, it is apparent that the film was not entirely moving as it should - there is slight overlap of frames - but the problem is not severe, just annoying.

Exposure of the film is fine, indicating that the shutter speeds are, at the least, close to the supposed values. I only actually used the faster speeds so I cannot vouch for the slower speeds - it is usually the slower speeds that play up first with old cameras.

Framing not quite right

Double exposure

This one is OK

Slight frame overlap

Ikonta 520

This is a medium format camera (i.e. takes 120 film) from Zeiss Ikon.  It is a half-frame camera - 6 x 4.5 cm negative - which is half of a standard 120 frame of 6 x 9 cm. The body serial  number tells me it was made in 1932.

Ikonta 520, front view

lens: Novar

focal length:  75mm

apertures: f/6.3 to f/32

focus range: 4'6" to infinity (that is the scale, actually about 4 feet)

lens fitting: fixed

shutter: Derval

speeds: 1/25, 1/50, 1/100, B, T

flash: n/a

film size: 120

The body is made from cast aluminium.  This body casting is shared between the Ikonta 520, Bob 510 and Nettar 515. It is quite hard to understand why Zeiss Ikon shared the body between three different camera lines instead of calling them all Ikonta (the oldest name) seeing as Bob, Ikonta and Nettar all come with a range of lenses and shutters and can be considered to be one range in effect if not in name.

So, this Ikonta.  It is an Ikonta 520 - more specifically, a 520E. The other variants are
520IT with a f4.5 Novar and a Telma shutter,
520F with a F3.5 Novar and a Compur Rapid shutter and
520L with a f3.5 Tessar and Compur Rapid shutter.

The lens is a Novar which is a triplet and performs surprisingly well once stopped down to f/8 or smaller.  Ikontas were also available with Tessars at a higher price and wider aperture Novars.  The Novar on this camera is quite a slow lens with a maximum aperture of f/6.3.  The focussing is front cell only, rather than the whole lens moving (giving not quite so good image quality) and the focussing scale is in feet indicating that the camera is an official import into the UK.

The shutter is an everset Derval (everset means it does not need cocking before firing as a Klio or Compur would).  This is a fairly crude (and so cheap) shutter with two blades only and only offers three speeds: 1/25, 1/50 and 1/100.  With a slow lens like this camera has, faster shutter speeds would have been superfluous, particularly with the slow, by modern standards, films available in the 1930s.

Detail of rim-set shutter adjuster on Derval shutter

The shutter is a dial set shutter which means that the speed adjustment is by a dial set above the shutter housing.  More modern shutters have a rim set adjuster which is a ring around the shutter housing.  This shutter does not have a V (=Vorlaufwerk) setting for delayed action and as is usual with cameras made before the late 1940s, there is no flash connection or synchronisation.

Ikonta 520, side view

As I mentioned, the maximum aperture is rather small at f/6.3 but the minimum aperture is surprisingly small - f/32 - so the range of exposures possible is still respectably large.

A standard photograph with this camera (as with the Bob 510 and Nettar 515) is in portrait format and in this orientation the shutter release is underneath the camera and is uncomfortable to use.  To take landscape pictures, the camera must be used on its side and the shutter release is on the side and easy to use.

The viewfinder is the cheap two frame style of viewfinder - a Newtonian finder.

This was an expensive camera in its day - according to Tubbs (Zeiss Ikon Cameras 1926 -39, published by Hove Camera Foto Books), it cost £4/10/0 new in the early 1930s and advertised by Zeiss Ikon in the British Journal Almanac for 1936 at £4/17/6.  That is £4.50 in new money but a week's wages for a working man would have been around £1/10/0 or £1.50. So this camera cost around a months income for a working man which is around £1,000 in today's money.

19/07/20123:  I have now finished my test film for this camera and the results are not good.  The lens is susceptible to flare (as I would expect on a lens from 1930 - coating of lenses had not been invented yet) and some of the flare is very strange, suggesting something other than ordinary flare - a glass defect, perhaps.

Blues festival in Lincoln Arboretum

One of our many buskers in Lincoln - very young but quite accomplished

Lincoln Corn Exchange in the Cornhill

Comparison between Ikonta 520, Bob 510 and Nettar 515:

These three cameras from Zeiss Ikon share the same aluminium casting for their bodies.  This makes them very similar cameras.  They all take 120 film and they all produce half-frame negatives of 6 x 4.5 cm.  The details, however, are different.  I shall give the differences between them one model at a time, starting with the oldest.

Ikonta 520

This camera was produced from 1931 and is using the old fashioned dial set shutter - the disc at the top with the word 'Derval' on it..  The adjuster for the aperture is at the bottom of the shutter housing and requires the user to turn the camera around so that the scale can be seen.  The lens is a Novar triplet lens.  There is also a leather hand strap on this camera and the catch to close the back is solid.

Bob 510

Next is the Bob 510 (sold in the UK as a Nettar 510).  This is a slightly later camera first produced in 1934 and has a more modern rim set shutter - the dial is now replaced with a ring around the shutter housing.  Shutter speeds and apertures are the same, but the aperture adjuster is now on top of the shutter housing, behind the speed selector.  This means that the user can adjust the aperture with the camera pointing at the subject.  Perhaps not a major advance  but will have been less frustrating to use.  The lens is now a Nettar rather than the Novar - still a triplet but a different design.  There is no hand strap on this camera and the catch for the back is less secure than on the Ikonta

Nettar 515

Last is the Nettar 515.  This is later again, 1937, and also has the rim set shutter.  The shutter is now a Klio (on non-Zeiss Ikon cameras known as Prontor) with more shutter speeds (up to 1/175 and a few slow speeds).  The aperture adjuster is still on top, behind the speed adjuster, and there is now a delay setting lever below the shutter housing.  As with the Ikonta, the lens is a Novar triplet.  This shutter requires cocking before use  and there is an ancillary shutter release button on the camera body.  There is also provision to fit an optional brilliant finder on this camera although mine does not have this.  This model also has no hand strap and it has the same catch as the Bob 510

All three together, oldest on the left, newest on the right.