The Minolta XK | XM SLR
Basic Camera Operations: Part IV

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Exposure Control Fundamentals

The two camera exposure-control settings are lens opening (aperture) and shutter speed. The size of the aperture determines the amount or volume of light reaching the film from a given subject and lighting. The shutter speed determines the length of time this light acts upon the film. Apertures arc expressed in F-numbers, which are larger for small openings and vice versa (e.g., F16 represents a small opening, F2 a large one). Shutter speeds are expressed in seconds or fractions thereof, which are the reciprocals of the numbers on the shutter-speed scales. At usual apertures, each F-number setting (e.g., F8) lets in twice as much light as the next numerically larger one (F11) and half as much as the next smaller (F5.6). Similarly, each shutter speed (e.g., 1/60 sec.) allows light to strike the film twice as long as the next higher speed ( 1 /125) and half as long as the next lower one (1/30). Total exposure on the film is determined by the combination of aperture and speed. Other things being equal, using the next smaller F-number will balance using the next higher shutter speed, and so on. A great range of combinations (e.g., F5.6 at 1/30, F4 at 1/60, F2.8 at 1/125, F2 at 1/250, etc.) will thus yield the same total exposure. The specific combination you choose under given lighting conditions will depend upon how much you want the greater depth of field of smaller apertures and the greater movement-blur preventing ability of faster speeds.

Exposure is determined by the combination of shutter speed and aperture. As the numbers on either the aperture ring or shutter speed dial increase by one increment, the amount of light striking the film is reduced by approximately one half. For example, the amount of light at 1/125 sec. is one half that at 1/60 sec., and the amount of light at f/16 is one half that at f/11. Brighter scenes require either faster speeds or smaller apertures or a combination of both which will give the same amount of exposure; darker scenes require the reverse. For example 1/1000 sec. at f/5.6 is the same as either 1/4000 sec. at f/2.8 or 1/125 sec. at f/16.

Shutter speed (sec.)







Aperture (f/number)







These simple combinations (and other factors relates) have made photography so exciting. As apertures and shutter speeds have their respective effect projects in the final image. With the camera's metering as a guide for an theoretical good exposure, you can alter the combinations to suit the effect that you like it to be. Basically, apertures varies the depth of field and shutter speed spells action or projects movement. Refer here for a separate article as this site will have too many duplicated /repetitive resources.

Note: the XK's maximum shutter speed scale is 1/2000 sec. Table above is merely reference.

The XK comes with an AUTO electro Finder as standard accessory. Since the XK can be regarded as the first professional grade SLR that utilizing a AE finder, it is interesting to find out how it works. The below illustration is the viewfinder display when a Auto Electro Finder is used. Other user
interchangeable finders.


Type: Eye-level pentaprism with built-in meter and automatic electronic and match-needle/manual exposure-control apparatus
Circuits: Incorporate monolithic and hybrid IC's with 41 transistors.
0.8X with 50mm lens
Visible in finder:
F-number, shutter-speed/function scale, meter/indicator needle, speed/function bar, light-emitting diode exposure warning signal.
Measuring range:
Built-in TTL CLC with 2 CdS cells for full-aperture metering with MC Rokkor Lenses, stop down metering with other Rokkor Lenses
Film-speed range:
EV 1 to EV 17 (e.g., 1 sec. at F1.4 to 1/2000 at f/8) with f/1.2 lens at ASA 12 to 6400
Shutter-speed/function dial:
AUTO, X, B, 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000 and 2000
Auto-exposure override:
- 2 EV to +2 EV stepless manual control
Compensation scale:
- 0.5 EV to +3.5 EV in half-step graduations
Power source:
2 silver-oxide batteries for shutter control in camera base (shared use)
50mm x 76mm x 65mm (1-15/16" x 3" x 2-9/16")
225 g (8-1/8 oz.)
Power switch for use in lieu of body Auto "


Metering Methods

Full-aperture metering with the stop-down/Lock-up button in its inner position is employed when MC Rokkor-X and MD Lenses are used with this finder, Stop-down metering is used with other than MC Lenses (e.g. close up attachment etc.).

Setting Film Speed

ASA setting.jpg
For correct exposure, the meter must be set for the effective exposure index of the film in use. To do this, turn the film-speed selector until the proper ASA value indication appears opposite its index dot. Dots between numbered graduations indicate ASA numbers as shown:

ASA/DIN Conversion Scale

ASA illus.gif

ASA scale.gif
A convenient scale for converting DIN to ASA film-speed ratings is located on the back cover of the camera.

A. Automatic Exposure Control

Automatic Operation

1. Turn the shutter-speed/function selector dial to align "AUTO" with the index. The speed/function bar will move to "A" on the scale in the finder.

2. Turn on power by touching and keeping your hand on the Auto "Senswitch" or using the switch on the finder.
3. Set the desired lens opening by turning the aperture ring on the lens barrel. The F-Number will appear above the frame in the finder, and the shutter speed indicated by the needle at the right of frame will vary automatically and steplessly to give proper exposure for the aperture and other settings with the light being being metered.
4. It is then only necessary to focus, compose your picture, and release the shutter.
5. The accurate range of shutter operation on automatic mode is 1/2000 to 4 sec. 1/2000 is indicated by the upper end of the indented area on the left side of the finder scale. For exposures longer than 1 sec., the needle will move progressively farther outside the indented area down to a point between "B" and "X." To determine whether the speed is longer than 4 sec., depress the auto-exposure override control radially and move it as far as it will go to the left. If the finder scale needle moves back to the figure "1 " or higher when this is done, the speed is within 4 sec. If the needle remains outside the indented area at any point below "1," the exposure set is longer than 4 sec.

Whenever a speed outside the proper auto exposure range is indicated, adjust the aperture or other conditions to yield a speed within it.

Note: If the shutter release button is pushed while power is off (i.e., when the Auto Senswitch is not being touched or the finder switch is not on) with the camera on automatic mode, the mirror will stay up and the shutter will remain open temporarily. Turning the shutter-speed selector dial to 'X' will return the mirror to its lower position and close the shutter at once. Even if this is not done, the electronic circuitry will reset the mirror and shutter automatically after about 30 sec. Toward not spoiling adjacent frames under certain conditions, however, it is advisable to reset the camera as quickly as Possible.

Exposure Warning Signal

Red blinking of the exposure warning signal below the scale in the finder indicates that light level has fallen below the lower limit of the meter's accurate sensitivity range on either automatic or match-needle/manual mode.

Whenever this signal is blinking, exposure set is not correct even if the shutter speed indicated by the needle falls within the acceptable range for automatic operation. It is thus important that exposure conditions be adjusted until the signal goes out.

Due to the characteristics of CdS under certain conditions, there may be an interval between the time the range is exceeded and the onset of blinking.

Auto-Exposure Override Control

To manually adjust exposure above or below the automatically set value, push in on the auto-exposure override control and rotate it to the right or left (for respectively more or less exposure) until the needle in the finder indicates the desired shutter-speed adjustment.

(For example, to give one stop more, i e. double, the exposure when the automatically set speed is "125," move the override control to the right until the needle points to "60."

To give 1/2 stop less exposure, i.e. 3/4 of the "125" auto setting, turn the control to the left so that the needle indicates a point halfway between "125" and "250.") Hold the control in the desired position while releasing the shutter, since it will otherwise automatically return to its neutral center position.

Eyepiece Shutter

Before I was exposed to the XK, I always thought the Canon A-1 was the first to incorporate this feature. For remote or unmanned operation or when the camera is set on a support and used without viewing on automatic mode, be sure to rotate the control at the right rear of the finder to close the eyepiece shutter.

This will prevent unwanted light from entering through the eyepiece and affecting the meter reading and exposure when the eyepiece is not being shielded by the photographer's head, as it normally would be.

EV Chart - Automatic Exposure Range with MC Rokkor 58mm f1.2
EV ChartSML.jpgPDF
file (288k)

From AUTO to Match-Needle / Manual Exposure Control



1. Turn the shutter-speed/function selector dial to align any step speed from 1/2000 through 1 sec. with the index. The speed/function bar in the finder will move to and remain fixed over the same scale number as that at which the selector is set, and the system is automatically switched over to match-needle/manual mode.
2. Turn on meter power by keeping your hand on the Auto Senswitch or using the switch on the finder. (This is not necessary if meter is not needed for manual exposure setting.)
3. To set proper exposure for light as metered the black needle is made to move and align with the fixed bar by adjusting the lens F-stop.
Note: Correct exposure cannot be obtained by needle alignment with shutter settings of "B", "X" and with speeds longer than 1 sec.
4. Needle alignment can of course be disregarded and any shutter speed (including those longer than 1 sec.) and aperture combination set for full-manual operation.

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Basic Camera Operations XK/XM/X-1: 5 Parts
Specification for XK/XM/X-1:
Main Reference Map for XK/XM/X-1:
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Additional info on
XK | XM Motor - by Satosh Oka
More images on XK Motor By : Stephen Schwartz (New)
XK USA fold-out Product brochure in HTML files
and a huge
PDF (1.3MB) copy. Contributed by : Mark Wasmer

Some fabulous views of the Internal Structures that made up of a Minolta XM by Gino Mancini (New);Three great images of a Minolta XM/XM Motor scanned by Hervé Prigent of France (New)

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Credit: Satosh Oka for his superp imagery of the XK Motor and XD-7; ® Stephen Schwartz, for his images of the XK Motor appearing in this site. Mark Wasmer, for his collection of the original marketing brochure. Oleg Volk, who has given me some help; Dick Sullivan whom I had used some references in his site; Hervé Prigent <>of France for his great scanned images from brochure of Minolta XM/XM Motor; Gino Mancini <> for his images of the internal structure of the XM; CYLeow ® , photo editor of the Star newspaper, Malaysia, Mr Poon from Poon photo for their input on Minolta older SLR bodies. Minolta, XD-7, XK, XM, X1, Rokkor, MC lenses are either registered tradenames or trade mark of Milnolta Optical Co. Ltd, Japan. A site dedicted to all Minolta fans worldwide. Made with an Imac.