Intrepid 4x5 Field Camera

The Intrepid 4x5 is one of the newest and least expensive large format field cameras.  It is made of wood, metal and some plastic and weighs in at 2 pounds, 14 ounces without a lens.  This is twice as much as my Nikon D7000 digital camera body, which weighs 1 pound, 7 ounces.  It is less than half as much as my Super Cambo monorail camera (9 pounds, 6 ounces).

Compared to monorail studio cameras, field cameras are lighter but have to give up some of the movements.  They have more movements than press cameras, which were intended to be hand held.  The Intrepid 4x5 has 42mm of rise (up movement from zero) and 30mm of fall (down) on the front standard (the part that holds the lens).  Front shift is 30mm left or right from center.  Front tilt is 45 degrees up or down.  Front swing is 45 degrees left or right.  The rear standard (the part that holds the focusing ground glass and the film holder) has 30 degrees of tilt up or down.  Limits to the flexibility of the bellows can constrain you from using all of the range of a movement.  Additionally, the back can be rotated 90 degrees to put the picture in either portrait (vertical) or landscape (horizontal) orientation.

The Intrepid can use 75mm (3") to 300mm (12") lenses.  A lens on a 4x5 camera has roughly the same field of view as a lens one-third that size on a 35mm or full frame digital camera, so a 75mm is like a wide angle 24mm lens and a 300mm is like a short telephoto 105mm lens.  A 75mm or 90mm lens focused at infinity needs a lens board (the part that attaches the lens to the camera) that has at least a 15mm recess.  Intrepid lens boards are 96mm wide by 99mm high, the same as a Linhof Technika lens board, a common size for 4x5 cameras.  If you buy a lens already on a Linhof lens board you probably won't need to get a new lens board.  Large format lenses are not currently produced; however, second hand lenses and some old stock are readily available.  A typical set of lenses might include a 90mm wide angle, a 150mm normal lens and a 210mm long lens.

The camera folds for storage or transport.  To set it up you loosen the large round knobs on the sides and raise the back standard to 90 degrees.  The front standard is attached to the base board by a threaded knob.  There are four threaded holes about 35mm apart on the base board to take the front standard.  You select one according to the amount of bellows draw needed (minimum extension is 75mm and maximum extension is 300mm).  Initially you want to zero the front standard using the marks on the camera.  The lens board fits on the front.

The 4x5 dimension is the nominal size of the film.  The picture is actually 3-7/8" by 4-7/8" (98mm x 124mm).

Picture taking with a large format camera is slow and methodical.  Film has to be loaded 2 sheets to a film holder in total darkness.  The camera has to be supported by a sturdy tripod.  The camera has to be focused and the picture composed by looking at a ground glass with the shutter open and the aperture wide open.  Perspective and depth of field can be controlled by the camera movements.  The shutter needs to be closed, the shutter speed and aperture set, the dark slide pulled out and the exposure made.  Then the dark slide is replaced, the film holder taken out, and the film taken to the lab to be developed.   

Intrepid cameras are made in Hove, England, UK.  https://intrepidcamera.co.uk/

 

A Speed-O-Copy for the Argus 21

The Speed-O-Copy was a copying accessory made by D. (David) Paul Shull (1883-1953), Los Angeles, California. Mr. Shull was an instructor in the Los Angeles public schools for 30 years, and an inventor. The Speed-O-Copy addressed the problem of focusing and framing a close-up photograph with a rangefinder camera. Unlike a single lens reflex camera (or most digital cameras) a rangefinder camera does not show the photographer what the camera sees through the taking lens. To do macro photography you ideally needed to get a camera's eye view. The Speed-O-Copy did this by putting a ground glass focusing screen at the same distance from the lens as the film plane of the camera. The Speed-O-Copy required a camera with a removable lens. The camera body would be attached to the camera plate and the camera lens to the lens plate. You would swing the focusing screen into position, focus the lens, swing away the focusing screen and move the camera into the correct position. Versions were made for the screw mount Leica, bayonet mount Zeiss Ikon Contax, etc. The version I have was made for the Argus 21 Markfinder camera.
 

The Speed-O-Copy acted as an approximately 8mm extension tube. With the Markfinder lens set at infinity the working distance to the subject was about 14 inches. With the lens set at 3 ft. the working distance was about 9-5/16 inches. Extension tubes and auxiliary lenses to change the working distance and magnification were sold separately. An adapter was available to use the Speed-O-Copy with a microscope. Camera supports also were sold.

Before the advent of office copiers, documents were commonly photographed to make copies to keep as permanent records.

Set up for focusing.

Set up for taking a picture.

Patent Drawing for the Speed-O-Copy

 

Mil-o Diaphragm Dial for the Argus C-3

This diaphragm dial differs a little from the Tiffen dial shown in December, 2023 (http://fourelementsinthreegroups.blogspot.com/2023/12/tiffen-quick-reading-diaphragm-control.html).  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 drop-in filter that is held in place 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 benefit of the diaphragm dial 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.