Mil-o Diaphragm Dial for the Argus C-3

This is a diaphragm dial that is a little different from the Tiffen dial.  Like the Tiffen dial, it slips over the pins on the Argus diaphragm dial and provides a side reading scale for the aperture.  It needs to be held in place by a Mil-o 19 mm screw-in to Series V filter adapter or else it will simply fall off.  The filter adapter holds a Series V filter using either an insert ring or a lens hood.  The adapter should not be screwed all the way tight against the diaphragm dial, or else it will pinch the dial against the face of the lens and the dial won't turn.  Like the Tiffen dial, you need to put an aperture index mark on the lens.The advantage is you can read the aperture with a Series V filter or lens hood attached.  The disadvantage is that the aperture scale moves around as the lens is focused.  I got this dial in a box with a Series V adapter and a lens hood.  The finish is bright chrome with engraved markings.

Mil-o was a trade name of Mr. Miller Outcalt (1912-2004), Hollywood, California, who sold photographic accessories.  At one time Mr. Outcalt distributed the Asahiflex single lens reflex camera made by Asahi Optical in the days before the Pentax, and the Yashica twin lens reflex camera.  Another of his trade names was "Kalt", which appears to be still in use for some photographic supplies.

Tiffen Quick Reading Diaphragm Control for Argus C, C2, C3

This is one of the many gadgets made for popular Argus cameras.  The Tiffen Quick Reading Diaphragm Control was intended to make setting the aperture on an Argus Cintar 50mm f/3.5 lens a little easier.  The Argus Cintar lens made from 1938 to 1958 has a small ring with a couple of tiny pins to set the iris diaphragm.  The Tiffen control ring fit over the ring and pins and made it easier to read the f/stop and set the lens, especially when a filter or lens hood was installed.  In 1958 Argus redesigned the Cintar lens to have a more conventional aperture ring, and the new lenses no longer needed the aftermarket control ring.  As a safeguard against losing the Tiffen control ring, it is a good idea to screw in a Series V filter adapter ring such as a Tiffen #502 or a Kodak No. 18 to keep the control ring from falling off if it came loose.  The control ring came in black with white markings or silver with black markings.  I think the silver version is a little better looking.

Black with white lettering

Silver with black lettering

Instructions for the Tiffen control ring.

Bolsey Model B2

The Bolsey Model B2 is a Bolsey Model B with the addition of flash synchronization and double exposure prevention.  The camera takes standard 35mm film in cassettes.  The B2 was introduced about 1948.  Peerless Camera Stores (New York City) advertised them in the October, 1948, issue of Popular Photography for $65.90.  The camera was discontinued in 1957.

Front

Rear

Top

Bottom

Interior

Ready to take a picture

After taking a picture

The body of the camera is made from aluminum and the dimensions are roughly 4-1/4 inches wide by 2-3/4 inches high by 2-1/2 inches deep. The camera has the controls on the lens, which was normally the case on leaf shutter cameras.  The lens is an f/3.2-f/22, 44mm, coated Wollensak Anastigmat.  The shutter is a Bolsey Wollensak Synchromatic leaf shutter.  The back of the camera comes off for loading film.  The path between the film cassette and the take-up spool is shorter than usual, and Bolsey ads claimed that you could get four extra pictures on a roll of film if you were careful about loading film.

The shutter release sets and releases the shutter in one motion.  The shutter has a moving peg that pops up to stop the shutter release from resetting after you take a picture.  The peg retracts when the film is wound and this allows the shutter release to reset.  To make a deliberate double exposure you push in the peg to allow the shutter release to reset.

The back of the camera has a depth of field calculator based on a circle of confusion of 0.05mm or 1/500 inch, which was typical for a miniature camera at the time, and a film reminder dial for Panatomic X (Kodak), Daylight Anscocolor, Tungsten Anscocolor, Daylight Kodachrome, Type A Kodachrome, Ultra Speed Pan (Ansco), Super XX (Kodak), Supreme (Ansco), Plus X (Kodak) and a blank space for when there is no film in camera.  None of the films are still in production.

The flasholder plugs into the openings on the left rear of the camera and takes a #5 or #25 flash bulb.

There are no strap lugs.  If you want a neck strap you need to use the leather camera case.  You also can use a strap that screws into the tripod socket.

A filter kit with a lens hood was available.  The lens takes a 24 mm series V adapter ring.

The Bolsey B2 is small and cute.  According to "Brass, Glass and Chrome" the camera was especially popular with women photographers.  You need to be careful with the shutter release to avoid camera shake.

Cimberland Mountain State Park, Crossville, Tennessee.  Ilford HP5 film.

This example has a very stiff (basically impossible) rewind.  Curiously it rewinds better with the back off. I need to give it a DIY CLA.

Diffraction and Circle of Confusion

Because of the wave nature of light, the image of a distant point of light is not an infinitesimal point, but a finite disc surrounded by a series of concentric rings.  The Royal Astronomer Sir George Airy worked out the mathematics of the effect of diffraction on an image in 1835.  The size of the disc depends on the diameter of the lens and the wavelength of light and is given by the approximate formula 

r = 1.22 * l * f / d  

r is the radius of the disc

l is the wavelength of light

f is the focal length of the lens

d is the diameter of the lens.

f / d being the focal ratio of a lens, we can use the focal ratio, N, instead of f / d.

r = 1.22 * l * N

In photography the diameter of the circle of confusion is usually used, so the diameter of the circle of confusion produced by diffraction is twice the radius of the Airy disc.

c = 2.44 * I * N

The wavelength of visible light ranges from about 400nm to about 700nm.  Using the middle of the range, 550nm, we get

c = 0.0011342 * N (in millimeters)

or

N = 882 * c

For an image to be seen as sharp in the final print the largest circle of confusion should be no more than the resolving power of the human eye viewing the final print at a comfortable distance.  Diffraction producing that much blur begins to affect the image quality.

On a 36x24mm, full frame sensor, c is typically given as 0.03mm.

N = 882 * 0.03

N = 26

Most full frame lenses stop down only to f/16.  A few stop down to f/22 or even f/32 (to increase depth of field).    

On a 17.3x13mm, Micro 4/3rds sensor, c is typically given as 0.0.15mm.

N = 882 * 0.015

N = 13

Under ordinary circumstances you would not stop down the lens on a Micro 4/3rds camera to more than f/11.

Sensor Size and Bokeh

Photographers like to call the blurred quality of a background in a portrait "bokeh."  You can get a numerical value for the size of the blur circle (circle of confusion) from an out of focus point of light at infinity starting with the thin lens formula:

1/f = 1/u + 1/v

f is the focal length of the lens, u is the distance from the lens to the object and v is the distance from the lens to the image.  When u is infinite 1/f = 1/v.  The distance from the lens to the image is equal to the focal lens of the lens.  You could express 1/v as 1/(f+e), with e being the distance the image moves as you focus on objects closer than infinity.  With a little algebra you can derive a formula for e as

e = f^2 / (u - f)

The amount of blur you get for an out of focus distant object is 

b = e / N

where N is the focal ratio of the lens.

Finally, the blurriness of the image on the final print depends on how much the image is enlarged. A Micro 4/3rds image has to be enlarged twice as much as a full frame image to make the same size print.

Let's aim our cameras at a subject 3m (10 ft) away.  We'll use a full frame digital camera with a 50mm lens set at f/2.8 and a Micro 4/3rds camera with a 25mm lens set at f/1.4.  The 50mm lens on a full frame camera has the same field of view as a 25mm lens on a Micro 4/3rds camera.  Both cameras see the same perspective because both are at the same distance from the subject.

Full Frame (36mm x 24mm)

f = 50mm

u = 3,000mm

N = 2.8

b = 50^2 / ((3,000 - 50) * 2.8)

b = 0.30

Enlarge the image 8 times to make an 8x10 print and you get a 2.4 mm blur circle.

Micro 4/3rds (17.3mm x 13mm)

f = 25mm

u = 3,000mm

N = 1.4

b = 25^2 / ((3,000 - 25) * 1.4) 

b = 0.15

Enlarge the image 16 times to make an 8x10 print and you get the same 2.4mm blur circle.

When you set up for the same perspective and field of view, to get the same background blur you need to open the aperture twice as much on the Micro 4/3rds camera as on the full frame camera.

Pushing and Pulling Kodak Vision3 Motion Picture Film

Kodak Vision3 camera film normally is developed for 3 minutes at 41 C (106 F).  If the film has been underexposed it needs to be overdeveloped by increasing the development time (pushing the film).  If the film has been overexposed it needs to be underdeveloped by reducing the development time (pulling the film).  Kodak recommends the following developing times for all Vision3 films:

    Push +2 stops: 4 minutes 40 seconds (56% increase)

    Push +1 stop: 3 minutes 40 seconds (22% increase)

    Normal: 3 minutes

    Pull -1 stop: 2 minutes 30 seconds (17% decrease)

Rapid development times are needed for motion picture film because such large volumes are involved.  A 35 mm print for a feature film will have a mile or more of footage, and the production company may expose more camera film than will go into the final print by a factor of 4 or more.

Commercial labs use automated machines to eliminate the human factor.  For developing by hand in a small tank at home it is recommended to have developing times at least 5 minutes long to get consistent results.  Reducing the developer temperature will increase the time needed to process the film, but may result in a color shift.  Some experimentation will be needed.

Sensor Size and Depth of Field

You see a lot of hand waving explanations of the effect of sensor size on depth of field.  I thought I'd do a little math on the subject.  Let's make three hypothetical pictures of a subject with three hypothetical cameras and keep the camera parameters as similar as we can.

The perspective of our picture depends on the distance from the camera to the subject.  The field of view of our picture depends on the focal length of the lens and the size of the image sensor.  A full frame camera (36x24mm sensor), an APS-C camera (24x16mm or 22.5x15mm sensor) and a Micro 4/3rds camera (17.3x13mm sensor) will have the same perspective of a subject 10' (3m) away.  A full frame camera with a 50mm lens, an APS-C camera with a 35mm lens, and a Micro 4/3rds camera with a 25mm lens have about the same field of view.

The maximum tolerable amount of blur on our final print usually is given as a circle about 0.25mm in diameter.  To make an 8x10 (20cm x 25cm) print the images produced by each camera have to be enlarged by different amounts, and the tolerable blur circle on the sensor depends on the amount of enlargement.  The image on a full frame digital camera will need to be enlarged 8 times, making the tolerable blur circle on the sensor 0.25 / 8 or about 0.031mm.  An image from a DX digital camera needs to be enlarged 12 times, making the tolerable blur circle 0.25 / 12 or about 0.021mm.  The Micro 4/3rds camera needs to be enlarged 16 times, making its tolerable circle 0.25 / 16 or about 0.016mm.

The hyperfocal distance is the distance a lens can be focused and have objects in sharp enough focus from infinity to 1/2 of the hyperfocal distance.  The hyperfocal distance depends on the focal length of the lens, the focal ration of the lens, and the tolerable blur circle (also called the circle of confusion).  A formula for calculating the hyperfocal distance of a lens is H = f^2/(N * c).  H is the hyperfocal distance, f is the focal length of the lens, N is the focal ratio of the lens, and c is the diameter of the circle of confusion.

The near and far limits of acceptable focus depend on the hyperfocal distance (H) and the distance the lens is focused (u).  The distance to the nearest point in focus is given by R = H * u / (H + u).  The distance to the farthest point in focus is given by S = H * u / (H - u).  The total depth of field is T = S - R.

Let's take pictures of a subject 3m (10 ft) away and calculate the depth of field for each camera.  We'll set the lenses at f/2.8.

Full frame digital:

H = 50^2 / (2.8 * 0.031) = 28,802mm or 28.8m

R = 28.8 * 3 /(28.8+3) = 2.7m

S = 28.8 * 3 /(28.8-3) = 3.3m

T = 3.3 - 2.7 = 0.6m

APS-C digital:

H = 35^2 / (2.8 * 0.021) = 20,833mm or 20.8m

R = 20.8 * 3 / (20.8 + 3) = 2.6m

S = 20.8 * 3 / (20.8 - 3) = 3.5m

T = 3.5 - 2.6 = 0.9m

Micro 4/3rds (17.3 x 13 mm) digital:

H = 25^2 / (2.8 * 0.016) = 13,951mm or 14.0m

R = 14.0 * 3 / (14.0 + 3) = 2.5m

S = 14.0 * 3 / (14.0 - 3) = 3.8m

T = 3.8 - 2.5 = 1.3m

The Micro 4/3rds camera has about twice the total depth of field as the full frame camera.  The APS-C camera has about 1-1/2 times the total depth of field as the full frame camera.  In general, to get the same depth of field as a full frame camera the aperture of the Micro 4/3rd camera needs to be twice that of the full frame camera (for example f/1.4 instead of f/2.8).