Mamiya C330f Professional Reparaturanleitung PDF herunterladen (Seite 11)

Mamiya TLR Summary 11

2.2 Lens hoods

The lens hood diameter refers to the square clamp-fit Mamiya hoods. They will only fit over slimline filters. Conventional screw-fit

hoods of suitable dimensions may be used in the filter thread. The Mamiya hoods are of two basic designs. The first design, used for

the 55mm, 65mm, 180mm, and 250mm were square with the upper flap hinged at the front. This permitted the angle of the top flap to

be set so that glare from the top of the hood was invisible in the finder. The hoods for the 80mm, 105mm, and 135mm lenses were of

a circular changing to square aperture rigid type. The 80mm and 105mm chrome lenses used 42mm hoods, the 80mm and 105mm

black, and both 135mm lenses used the 48mm hood. All the 180mm and the 250mm lenses used the same hood. These hoods are

generally metal. There is also a telephoto lens hood for the chrome series that consists of two rigid square shades in a single plastic

unit. (Compiler's Note: This item is huge!)

2.3 Optical design

There was a change in physical and optical design between the chrome and black series lenses. One known effect is that the 105mm

D and DS lenses have a different back focus from the 105mm chrome and the early 105mm black. This means that the scale on the

C330 and earlier bodies is incorrect for the later lenses. The C330s (and probably most C330f) have scales for both 105mm lenses. It

should also be noted that earlier bodies do not have scales for the focal lengths introduced later. The lenses will function, however.

The 180mm (black) and 180mm Super (black) are different optical designs, but appear to share the same back focus.

2.4 Lens coating

This is a contentious issue, probably stemming from a lack of understanding of lens coating in general. Lens coating has been

common since the Second World War, initially as general single coating, then as single coating tailored to individual lens

performance, and most recently coating of internal elements and multiple coating for optimum corrections. Coating is used to reduce

reflection from the surface that contributes to flare and lack of contrast. It also helps compensate for minor variations in glass batches,

and in multi-coating the performance over a range of wavelengths is made more consistent.

The chrome lenses were single coated, and the black series had single coatings which may have extended to various lens elements.

Some late black series lenses have had multi-coating, but there is a lack of substantive evidence as to when it was introduced, and on

which lenses. The 55mm, 80mm S, 105mm DS, and 180mm Super are the most likely candidates, as these were later or more extreme

designs.

Even the best of these lenses won’t have the class of coatings that appeared in the 1990’s.

2.5 Shutters and flash synchronisation

The original chrome lenses were fitted with shutters having a maximum speed of 1/400 second (Seikosha-MX). Later chrome lenses

were improved to a 1/500 second top speed, giving a conventional range from 1 second to 1/500, plus B (Seikosha-S). The

changeover seems to have occurred during the production life of the C2. The final black series lenses used a Seiko shutter with 1

second to 1/500th second plus B settings. Some shutters exhibit a leaf with a raised tip. This ‘anti-crash’ feature is intended to reduce

the chance of the shutter blades locking when closing. It usually indicates a newer shutter, often with a blue insert in the shutter

cocking arm. The 80mm f3.7 black lens had a Copal shutter. At least one Seikosha-MX shuttered 80mm lens was labelled ‘f=8cm’.

The lenses all have integral leaf shutters, providing X and M synchronisation at all speeds. Connection is via a standard 3mm co-axial

PC cord on each lens. Lenses which have been in professional hands sometimes have the flash synchronisation levers fixed in the 'X'

setting. This is usually achieved by cementing a small stop to the lens barrel. Obviously the inadvertent shift to 'M' with electronic

flash had happened once too often! There is around 200 milliseconds delay between releasing the shutter (and closing the flash

contacts) and the shutter opening on the 'M' setting. This delay was to allow flash bulbs time to reach full illumination. Since the delay

is a mechanical process, and the M setting is rarely used, longer delays are quite common and the shutter may stick.

The PC connection on most lenses consists of a hollow stud. The centre hole is one side of the flash contact, and connects to a wire

running to the shutter assembly. The outer portion of the stud is the other contact, and connects to the lens mounting through its

mounting screws. Intermittent flash problems may be caused by the mounting or wire becoming loose. This can be tested using a

resistance (Ohm) meter. [A resistance meter applies a negligible current and voltage across its probes. Higher voltages or currents

may result in damage.] Set the lens to a slow speed (say 1 second), and cock it. Insert the PC cord, and hold the resistance meter

probes to the terminals at the other end of the cord. When the shutter is fired, the meter will register if the flash circuit is made. A

slow speed is necessary to be sure the meter has time to react.

Some later lenses, such as the 105mm DS, have a shrouded PC socket that appears less vulnerable to accidental damage or loosening.

At the risk of stating the obvious, these shutters work in fixed steps. Intermediate speeds should not be set. Intermediate apertures can

be set.

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