Showing posts with label exposure values. Show all posts
Showing posts with label exposure values. Show all posts

Saturday, 4 October 2014

Yashica Minister III


This is a rangefinder camera from Yashica that is pretty standard for its time.  It is almost exactly the same size as Zeiss Ikon's Contessa LKE of the same period and looks very similar as well. It is slightly larger than Voigtlander's Vitomatic II which is slightly earlier.

lens:  Yashinon-DX
focal length:  45 mm
apertures: f2.8 to f22
focus range: 0.8 m (2.6 ft)
lens fitting: fixed
shutter: Citizen
speeds: 1 s to 1/500 s
flash: PC socket
film size: 35mm

The camera is quite heavy - 656g including a 24 exposure cassette of film. This weight is going to tell at the end of a busy day photographing. It is 135 mm long and 85 mm high. The body is 35 mm thick which increases to 85 mm when the lens is included.

Yashica Minister II ((C) John Margetts)
 There are not many controls on this camera - it is entirely manual. On the top plate, starting on the left, is the rewind crank. This also pulls up to release the cassette for loading/unloading. Next to this is the accessory shoe. In flash terms, this is a cold shoe. next to this is the meter dial. This has two components: ASA setting and meter read-out.  ASA can be set between 10 and 400 ASA (new style). Behind this is the read-out for the meter. This gives you EV numbers between 4 and 18. In use, you choose the EV number the needle is pointing to and transfer this number to the outer most ring on the shutter housing. You are quite at liberty to ignore this if you want to - if you are using a hand-held meter, perhaps - or using the flash.

Next in line is the shutter release button, which is towards the front of the top plate. This is a small (by modern standards) chrome plated button, threaded for a standard cable release. Beside this is the film advance lever. Right on the right-hand end of the top plate is the frame counter. This is automatically reset when you open the back and counts up from 1.

The front of the camera has the viewfinder and rangefinder windows and the shutter housing with lens. The viewfinder is quite large and bright and has bright-line frame lines. In the centre of the viewfinder image is the yellow rangefinder spot. This is plenty large enough without getting in the way and is nice and bright. The rangefinder is coupled to the lens.

The shutter is made by Citizen - no model name is given - and it is a leaf shutter. The shutter housing is fairly large and central.  Partly, it looks large compared to Compur and Prontor shutters of the period as it is straight sided rather than stepped. There are three adjustment rings on the housing. The inner most, marked in green, is the focussing ring. This focusses from 0.8 metres to infinity and is marked in both metres and feet. Strangely, there is no pointer for this scale and the pointer position (where the pointer would be if there was one) is well to the right of centre. I suspect the designer thought there was no need for a pointer as the user is intended to use the rangefinder but I would be more comfortable if there was one. 

The outer most adjustment ring, marked in red, is where you set the EV numbers from the light meter. Even though the meter only offers numbers from 4 and higher, the ring is marked for 2. Setting this ring gives the user a range of both shutter speeds and apertures. Once the EV number is set, you can rotate the middle adjustment ring - the shutter speed ring - to change the shutter speed. Doing so also alters the aperture so that the required exposure is maintained. There is no direct method for adjusting the aperture, but there is a small window immediately behind the shutter speed ring showing the set aperture. If you want a particular aperture (which I usually will) you can alter the shutter speed until the desired aperture is displayed in the window.

Minister III - rear view ((C) John Margetts)
On the base of the shutter housing is a small lever which sets the delay timer. Although we are always told not to use this on an old camera, I can report that it works very well on this particular old camera.

In the front of the shutter housing, around the lens, is the light meter sensor. This is a selenium sensor and so needs no battery - there is no problem with this camera of having to find a replacement for an obsolete mercury battery. Many 'experts' will tell you that old selenium meters are too unreliable to be worth using. This is based on the fact that the light sensitive surface deteriorates with time and then gives low readings. While this is true, if the meter has been kept in the dark except when being used the deterioration over 60-odd years is so slight as to present no problems. I have many selenium meters that are 60-odd years old and they all give accurate readings and I shall continue to use and trust them. I doubt those 'expert' who decry using old selenium meter have actually tried using them.

The advantage of having the light meter sensor around the lens is two fold. Firstly, it is always pointing in the same direction as the lens and secondly, if a filter is used, it fits over the sensor and no adjustment of the meter reading is required.

The lens is a Yashinon-DX lens (I do not know the significance of the 'DX'). This lens has five elements in four groups and is reputed to give very good results. The focal length is 45 mm so the angle of view is very close to the human eye and accordingly will give natural looking results. The largest aperture is f2.8 which might not seems to be particularly fast, but, to be honest, I never shoot much wider than f8 so I just do not care that the lens does not go to f2 or f1.8

This camera has a PC (Prontor-Compur) connector for the flash and this is, idiosyncratically, place on the left-hand end of the camera.

The base plate of the camera has the usual tripod boss - this is the 1/4 inch Whitworth thread - and it is placed centrally behind the lens which means the camera will be stable when on a tripod. Also on the base is a recessed button to free the internals for film rewind and, at the opposite end, a recessed button for unlocking the back. I find this hard to use - you need to slide it to one side and then press it in. Perhaps with time I will find it natural, but not yet.

27/10/14

I have now completed my test film and I am quite impressed.  The camera is easy to use - the light meter works well as does the viewfinder.  I had some flare when shooting into the sun but I did not use a lens hood. Generally, the lens has good contrast and colour rendition.

I took the picture of the reed flower to test the lens at maximum aperture.  The flower is nicely sharp and the background not sharp - as I would want it.  These were all taken in October, so not a lot of sun about.

The cathedral from the footbridge over Broadgate, Lincoln.

The Strait, Lincoln


main railway line, Lincoln

Reed flower

Young Love

Thursday, 5 September 2013

Contina IIa

Zeiss Ikon's Contina camera was a long lived and varied series of cameras.  The series started as the Ikonta 35 which was a post-war version of the 120 format Ikonta adapted to take 35 mm film.  This camera became two series of cameras - the Contessa and the Contina; the first Contessas and Continas were folding cameras. The Contessa version was more up-market than the Contina version. I have already written about one of the Contessa line - the Contessa LKE. The Contessa line have better lenses (Tessars) and coupled light meters and rangefinders. The Contina range have cheaper lenses (Novar, Novicar and Pantar) and the light meters, where present, are uncoupled. I have also written about the Contina line elsewhere - the Contina Ic.

lens: Novicar
focal length:  45mm
apertures: f2.8 to f22
focus range: 1m to infinity
lens fitting: fixed
shutter: Prontor-SVS
speeds: 1 second to 1/300 seconds
flash: PC connector
film size: 35mm

Contina IIa - front view, meter window closed
To make identifying and placing Contina cameras as difficult as possible, the Contina series split into two lines of cameras simultaneously.  The original Contina folding camera  became the Contina II folding camera with a light meter and then a series of derivatives. That original Contina folding camera, at the same time, became the Contina I rigid camera - no light meter or rangefinder - and then a series of derivatives.
Front view - meter window open

So, at any one time after 1953 there were two different Continas available, both just designated Contina. I have been referring to Contina I, Contina II, Contina Ic, Contina IIa but I don't think those were names offered by Zeiss Ikon, rather us collectors use them to make sense of the mish-mash of models.

Daniel Jiménez has produced a 'family tree' of the Contina series which he has given me permission to use here:

Copyright Daniel Jiménez
Daniel has a useful camera blog which can be found in an English version here. He also has a much larger Spanish version here.

This camera - is a Contina IIa. It is derived from the Contina II which was a folding camera but this version does not fold - that is, it is rigid. It is a compact and solid camera measuring 120 x 65 x 85 mm and weighs 567g. It offers a built-in but uncoupled light meter and an EV enabled shutter. It was not a cheap camera - it cost £43/15/1 in 1957 (in old money, or £43.76 in new money) which, given the average male wage in 1957 was £9.00 means this camera cost the equivalent of £2,500 in 2013 values. The version with a Novar lens only cost £36/12/7.

The top plate of the camera has a number of  items on it. On the left is a small rewind knob. I prefer these to the small folding cranks that became ubiquitous in the 1960s. When you first turn the rewind knob, it raises itself by one cm. This is above the height of the centre of the top plate and makes it easier to hold and turn.

rear and top view
Next to the rewind knob is an accessory shoe. At the time that this camera was made (1956/58) this was more likely to be used for a separate rangefinder than a flashgun. There are no electrical contacts in the accessory shoe so it is a cold shoe.

Next to the accessory shoe is the light meter window and the light meter control knob. Visible in the window is a needle connected to the light meter. The brighter the light, the more this needle moves towards the rear of the camera. Also in this window is a white circle which moves in response to the user moving the control knob. When the white circle is over the needle, the correct exposure can be read off the scale around the control knob. This is mostly in EV values - more later. In the centre of the control knob is the setting for the film speed. This camera was made in 1956/8 and uses the film speed standards in place at that time. A few years later (1960), the American Standards Association (ASA) revisited their film speed standard to produce the later ASA standard now known as ISO. The German DIN system remained unchanged so on this camera 21 DIN = 40 ASA rather than the later standard of 21 DIN = 100 ASA (ISO) - I always use the DIN standard with old cameras to make sure I do not get it wrong.

On the far right of the top plate is the film advance lever. This moves through about 200 degrees to advance the film and cock the shutter. The lever is all metal and only curves a very slight amount which I find makes it uncomfortable to use. In the centre of the film advance lever should be the frame counter. I can make no comment about this as a prior owner has removed it. Looking at the state of the metal that is left, I suspect a very amateurish attempt at a repair.

The front of the camera has four items - meter window, viewfinder window, shutter housing and flash PC connector. The meter window contains a two cm by one cm lens covering a selenium photoelectric cell.  This does not need any batteries, which I always reckon to be a good thing.  Most camera electrics from the 1960s to 1980s use mercury cells which are now illegal in just about every country there is. This window has a hinged cover - to open it, you lightly press the right-hand end (as the camera is to your eye). Selenium meters get a poor press as the photoelectric cell will deteriorate with time. However, if the cell is kept in the dark it only deteriorates very slowly, so this cell being covered, it has not yet (in 57 years) deteriorated enough to worry about. This is a single scale meter - an earlier version of the Contina IIa had a dual scale meter with a small window in the hinged cover.

Next to the meter window is the viewfinder window. This has quite a small eyepiece and a plain view with no bright lines. I find I cannot use it while wearing my glasses.  The Contina Ic, which I also own, has a much larger eyepiece - this was made just a few years later in the early 1960s.

In the centre of the front is a square chrome bezel containing the shutter.  This is a Prontor-SVS from Gauthier. This works on the EV system.  The light meter gives you an EV value from between  three and eighteen and you transfer this number to the shutter - you have to press a small tab on the shutter housing to get the EV ring to turn. Each EV number gives you a small range of shutter speed and aperture settings.  If you turn the EV setting ring without pressing the small tab, different speed/aperture combinations will present themselves to the mark at the top of the housing. For very low light levels, the shutter speeds are in green - you cannot set these, but you can read them.  To use them, turn the control ring on the shutter housing to B and read off a speed next to the aperture you want to use.  You then need to time the exposure yourself - the speeds are from four seconds to sixty seconds and you can count this quite accurately without a watch.

The lens is a Novicar lens (a Novar lens was also available) which I have found to be excellent if stopped down to f5.6 or f8. It is threaded for 27mm filters.  Maximum aperture is f2.8 and its focal length is 45 mm. Focusing is from about three feet to infinity (one metre to infinity). The throw of the focusing is only about 120 degrees, so very accurate focusing is not possible, but with no rangefinder, this camera was always going to rely on depth of field.

On the lower right of the shutter bezel (looking at the camera) is the flash PC (Prontor-Compur) connector.  This is the only means of connecting a flashgun. On the side of the shutter housing there is a selector for M or X - Magnesium or Xenon  - flash. M is for flash bulbs and X for electronic flash. With M, the flash is fired slightly before the shutter opens to allow the burning of the flash bulb to reach its maximum while the shutter is fully open. With X, the flash is fired as the shutter blades are fully open as electronic flash does not require time to reach its maximum intensity. This selector also has a V setting. This means Vorlaufwerk and is German for self timer. Moving the selector to this position causes an eight second delay between pressing the shutter release and the shutter firing. It is never a good idea to try this facility on an old camera as it might well cause the shutter to stop working permanently.

Rear/internal view

The back opens by pulling down a small catch on the lower right-hand edge. The back is hinged and there is a single light seal - a piece of velvet right by the hinge. The back itself has the pressure plate and a tensioning roller that goes by the take-up spool. Around the film mask are two machined film guides - showing as bright lines in the photograph above. The pawl for the rewind mechanism can be raised to enable fitting a film cassette and then lowered to secure the cassette.

24-December 2013


I have now finished my test roll of film - Agfa Vista+ 200 ISO from Poundland (yes, £1.00 per roll!). As expected, the camera works well. The only awkward thing was setting the EV values on the shutter as the mechanism is rather stiff.  I definitely would not want it too loose but it would be nice for it to be a bit easier to alter. The frame counter is missing on this camera - I assume due to a botched repair by the previous owner. It does not affect the camera's functionality at all and got me the camera at a bargain price. Below are a selection of pictures from the test film.

Pottergate Arch, Lincoln


Fountain in Lincoln Arboretum


Rockabilly Buskers, Lincoln


Lincoln Shoppers getting ready for Xmas


Foreign Buskers, Lincoln


Wednesday, 15 August 2012

Light (or exposure) meters


Light meters (which are also called exposure meters) are a modern invention and early photographers had to guess their exposures and rely on experience to get it right.  An early system used to make guessing easier was to use the Sunny 16 rule which says:
  • "On a sunny day set aperture to f16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight." 
 (from Bernhard J. Suess (2003). Mastering Black-and-White Photography, Allworth Communications. ISBN 1-58115-306-6)  So, if you are using Ilford FP4 film, which is ISO 125, on a sunny day you set the aperture to f16 and the shutter speed to 1/125 seconds.  This will generally give you a usable picture even if not a perfectly exposed one.  You do need to be aware that the amount of light on a sunny beach will be more than the amount of light in a sunny field - entirely due to the amount of reflected light.  You can easily adjust either the aperture or the shutter speed to compensate.  You also need to be aware that the amount of light present on a sunny day depends on how close to the equator you are.  A photographer in Norway using the Sunny 16 rule will get a very different result than a photographer in Nigeria would.  I have been trying this Sunny 16 rule out in Lincoln this week and in the middle of the day it produced the same exposure as my Ikophot exposure meter suggested.  By four in the afternoon, the Sunny 16 rule was a whole stop out.

A better system was the extinction meter.  This used a piece of translucent celluloid that was painted black apart from a series of grey numbers.  Each number was printed in a darker shade of grey than the last number.  So, in my Braun Paxette, the number 1 is nearly white and the number 16 is nearly black.  In use, the user looks through the extinction meter and notes the darkest number that is visible.  This number is then looked up in an exposure table to get suitable aperture and shutter speeds.  This picture of my Braun Paxette show one of these tables.  It is set up for 50 ASA (ISO) film and tells you to halve the exposure for 100 ASA film and double it for 12 ASA film (films were much slower then than we are used to now).  This chart refers to 'diaphragm' rather than 'aperture' but it is the same thing.


Extinction meter table on my Braun Paxette

These, although simple and not able to go wrong, had their drawbacks.  They depended on the quality of the eye sight of the user and that is very variable.

The next development was the electronic light meter.  Initially, these had a cell made from selenium that produced a small electrical voltage on exposure to light.  This voltage was then used to move a needle across a scale.  This needle would then point to an arbitrary number that has to be set on a scale.  The scale then indicates a range of appropriate aperture and shutter speeds.  It is tempting to think of these as EV numbers but they are not - at least are not on the three light meters I own.  These worked very well in reasonable light but were poor performers in poor light.  These fell out of fashion and were replaced by CdS meters.  The advantage of selenium meters is that they do not need a battery to work.  A big disadvantage is that they lose sensitivity with time.  Towards the end of their useful life they give a low reading which will eventually cause over-exposed photographs.  For this reason, some people will not use old selenium meters but my old (fifty years old, plus) meters all agree with my modern light meters.

 I suspect that the rate of deterioration depends on how the meter has been stored over the years.  If the meter is in the dark inside a case apart from when actually taking a reading, the deterioration doesn't seem to matter over a period of sixty or so years.

The next development was the CdS meter (Cadmium Sulphide).  These do not produce a voltage on exposure to light but act as a resistor that changes its resistance to electricity on exposure to light.  These always need a battery to work to provide the voltage.  Most modern light meters work this way.  These work in much lower light levels and do not significantly deteriorate with time.  The draw back with these is that battery technology changes and it can be hard (or impossible) to find batteries for older CdS meters.  In particular, mercury batteries are no longer made and the modern equivalents produce a different voltage which alters the accuracy of the meters.

A lot of meters from the 1950s used what are called Exposure Values (EV).  The idea is that you set your shutter to the indicated EV and this sets a combination of shutter speed and aperture.  As you then alter the aperture, the shutter speed will alter in unison - and vice versa.  I like the system but many people do not.

Here is a table of EVs and their associated aperture/shutter speeds:
 
Table 1. Exposure times, in seconds or minutes (m), for various exposure values and f-numbers
EV f-number
1 1.4 2 2.8 4 5.6 8 11 16 22
−6 60 2 m 4 m 8 m 16 m 32 m 64 m 128 m 256 m 512 m
−5 30 60 2 m 4 m 8 m 16 m 32 m 64 m 128 m 256 m
−4 15 30 60 2 m 4 m 8 m 16 m 32 m 64 m 128 m
−3 8 15 30 60 2 m 4 m 8 m 16 m 32 m 64 m
−2 4 8 15 30 60 2 m 4 m 8 m 16 m 32 m
−1 2 4 8 15 30 60 2 m 4 m 8 m 16 m
0 1 2 4 8 15 30 60 2 m 4 m 8 m
1 1/2 1 2 4 8 15 30 60 2 m 4 m
2 1/4 1/2 1 2 4 8 15 30 60 2 m
3 1/8 1/4 1/2 1 2 4 8 15 30 60
4 1/15 1/8 1/4 1/2 1 2 4 8 15 30
5 1/30 1/15 1/8 1/4 1/2 1 2 4 8 15
6 1/60 1/30 1/15 1/8 1/4 1/2 1 2 4 8
7 1/125 1/60 1/30 1/15 1/8 1/4 1/2 1 2 4
8 1/250 1/125 1/60 1/30 1/15 1/8 1/4 1/2 1 2
9 1/500 1/250 1/125 1/60 1/30 1/15 1/8 1/4 1/2 1
10 1/1000 1/500 1/250 1/125 1/60 1/30 1/15 1/8 1/4 1/2
11 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30 1/15 1/8 1/4
12 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30 1/15 1/8
13 1/8000 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30 1/15
14
1/8000 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30
15

1/8000 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60
16


1/8000 1/4000 1/2000 1/1000 1/500 1/250 1/125
17



1/8000 1/4000 1/2000 1/1000 1/500 1/250
18




1/8000 1/4000 1/2000 1/1000 1/500
19





1/8000 1/4000 1/2000 1/1000
20






1/8000 1/4000 1/2000
21







1/8000 1/4000
EV 1 1.4 2 2.8 4 5.6 8 11 16 22
f-number

To my light meters:

I have four old meters, each of the selenium type.  They are a Weston Master III, a Leningrad 4, a Ikophot and a Bewi Automat.  The Weston does not work - I tried to adjust the zero setting and managed to wreck the meter.  The blame for this lies entirely with me, not Weston’s design or manufacturing standards.

First, the Weston.

This is a Weston Master III

Weston Master III
It is the most complicated meter of the three I have - presumably it will do more than the other two.  The draw backs for me is firstly there is no ASA or DIN setting, it uses instead Weston values which are their own proprietary system. As films do not come with a Weston speed marked on them, it makes it unnecessarily difficult to use.  Secondly, I find the plethora of black and white marking difficult to distinguish.  As I mentioned earlier, I managed to break this meter, so my complaints about it are moot.

Secondly, Leningrad 4:
Leningrad 4
This is much simpler in layout than the Weston and much easier to use.  The needle points at red numbers, these red numbers are then set against a large pointer on the other end of the meter and the aperture/shutter speed combination are read off a black and white scale.  The film speed can be set in either ASA or DIN and will work with modern films with ISO speeds as they are the same as ASA.  A note of caution:  these red numbers are NOT Exposure Values - they seem to be arbitrary numbers and are different to the equivalent numbers on the Ikophot meter.

Thirdly, Zeiss Ikon Ikophot:
Zeiss Ikon Ikophot
This mirrors the Leningrad in as much as the meter needle points to red numbers and the red numbers are then aligned against a red pointer.  The aperture/shutter speed combination is then read off the scale - aperture in black and shutter speed in white on red.  Again, film speed can be set in either ASA or DIN.  A note of caution:  these red numbers are Exposure Values but only for 50 ASA/18 DIN film (I expect 50 ASA/18 DIN was seen as standard by Zeiss Ikon).  It is possible to use them directly on cameras with a EV scale on the shutter, but you will need to adjust for the speed of the film you are using.  This is simple enough - for 100 ASA, 21 DIN film, subtract 1 from the EV; for 200 ASA, 24 DIN film subtract 2 from the EV and for 400 ASA, 27 DIN film, subtract 3 from the EV.

The DIN/ASA scales on this meter are a bit unique.  DIN 21 SHOULD be ASA 100, but it is ASA 80.   I use the DIN exclusively and that works just fine.  I suspect using the ASA scale would also be fine as the difference between 80 and 100 is fairly small (1/3 of a stop).  As DIN is a German standard and Zeiss Ikon are a German firm, I would expect them to get DIN right.

Not cheap - it cost £10/13/5 in 1957 - which was just over an average man's weekly wage (so about £500 in 2013 values).

This is the meter I most often use as it is nicely made, feels good in the hand and produces satisfactory results.  A scanned copy of the Ikophot manual is available for download as is a scanned copy of Zeiss Ikon's 1930s exposure guide.

Lastly, my Bertram Bewi Automat.

Bertram Bewi Automat
This is a German meter (made in West Germany).  Bertram have been making light meters since 1928 . This meter works differently from the meters above.  For one thing, it has a digital read-out rather than an analogue needle pointing to a scale. 

The meter is rather larger than is usual for analogue meter - it measures 90 x 65 x 25 mm not including the activating button.  It is encased in ivory plastic.

 The only control is a ring to set the film speed.  This is calibrated in ranges. For instance, the DIN setting is a range of three numbers - 11-13, 14-16, 17-19, 20-22, 23-25.  That is one stop difference between each range.  Given the exposure latitude of film that is plenty accurate enough.  There are also ranges for ASA and Weston (ASA is the same as ISO and Weston is a defunct film speed system devised by the makers of the Weston series of exposure meters.

Using the meter is also different to analogue meters.  If you point this meter at the scene you intend to photograph, nothing happens.  You need to point the meter, depress the activating button for about three seconds and release.  Once you have done this, the shutter speed scale lines itself up with the aperture scale and you can read off suitable combinations of aperture and shutter speed.

The read out also has exposure values indicated - under L on the aperture scale.  These are adjusted for film speed and can be set directly on an EV enabled shutter.