Pentax 645N Autofocusing Comes To Medium Format SLR

With its permanently attached right side handle/grip the boxy Pentax 645N is very easy to hold for horizontal or vertical compositions. The front is relatively clean and uncluttered since most operating controls are found on the top and rear.

Evolution is inevitable in all camera formats. The past two or three decades have witnessed a vast degree in sophistication, automation, and electronicization of all types of photo equipment. The Pentax 645N was the first medium format SLR to incorporate autofocusing. There are others now, but this was the original and Pentax got there first just as they did decades earlier with practical Through The Lens (TTL) metering in the pioneering Asahi Pentax Spot-matic introduced in 1964. Who knows what's next? Perhaps sometime early in the soon to arrive next millennium an autofocusing large format camera will come into being. Only time will tell.

I personally believe most medium and large format photographers tend to be more deliberate, painstaking, and precise about each image they expose. Far more so than the typical 35mm user, who often shoots away indiscriminately, burning up excess film just because it is so inexpensive. By virtue of this dedication, they often keep extensive written exposure records, recording exactly how each picture was made. This new 645N camera greatly simplifies this task as it imprints complete data pertinent to each exposure onto the negative or transparency film, just outside the image area. This imprinted data includes the frame number, exposure mode, shutter speed, aperture, exposure compensation value, metering mode, and lens focal length. This automatic and thorough imprinting sure saves a lot of tedious note keeping for those of us who normally manually record copious amounts of data about each exposure. This is a truly outstanding feature I would cherish in any camera--and it's built into the Pentax 645N.

The imprinted data on the edge of every image includes the frame number, exposure mode, shutter speed, aperture, exposure compensation value, metering mode, and lens focal length. This automatic and thorough imprinting sure saves a lot of tedious note keeping. This particular image shows it was frame No. 13; Time Value exposure (TV); 1/2 sec at f/19; no exposure compensation; center-weighted metering; 400mm lens.
Photos © 1999, Robert E. Mayer, All Rights Reserved

If you are not particularly familiar with medium format cameras, don't be lulled into the belief that these are particularly easy loading and operating cameras. They do require a fair amount of user know-how and dexterity when compared to their nearly totally automated 35mm or APS format cousins. Just loading the light-tight black paper backed 120 film into the film holder is slightly tedious. First the empty metal spool has to be placed into the take-up slot and the new roll leader has to be threaded into a slot in the empty spool. Then the film is wound slightly until an arrow (on the backing paper) shows opposite a mark inside the camera. This is done before you even place the holder into the camera. Extra film holders are available that can be pre-loaded for faster film changing when working on fast paced events or subjects. Then you must be sure to check, and if necessary, reset the ISO setting since roll film does not have DX coding marks to automatically set the ISO film speed. However, once the film is loaded and the proper ISO film speed is set, operating this new 120 AF SLR is quite similar to a conventional autofocusing 35mm SLR such as most of us are familiar with. It even is held similar to a 35mm SLR since it includes a built-in grip on the right side that often is an add-on extra on other makes of medium format SLRs.

The camera's bayonet-mount lens is changed similar to those on 35mm cameras (by aligning red dots) and once the lens and shutter speed dials are set to the green "A" (Automatic) position, everything is totally programed automatic in operation. A built-in motor drive advances the film at 2 fps normally, but you have an optional consecutive advance mode, which keeps tripping the shutter and advancing the film as long as the shutter release button is depressed. You get 16 images on 120 film or 33 on 220 film. The actual film image is 2.7 times larger than that of standard double format 35mm film. In addition, there is powered film advance winding to the first frame and run-off of the tail leader when the 16th frame is finished. So film transport is very automated leaving you to concentrate on the subject visible in the viewfinder. Naturally, you also have the option of selecting aperture or shutter priority automatic or complete manual operation when desired.

Even bright fall sunlight shining directly into the camera lens through colorful leaves did not cause any metering problems. (Fujichrome 100 RDP 75mm lens, 1/250 at f/11, center-weighted metering.)

Any of three metering modes are easily selected by simply moving a lever located below the shutter speed dial. The choices are multi-segment, center-weighted, and spot metering. The multi-segment metering is classified as "Dual Six Segment," read by two sensors located on both sides of the viewfinder measuring the lighting condition in two different areas. A wide sensor covers the entire field while a narrow sensor monitors just the central area. When dictated by varying subjects you can choose pinpoint spot metering or conventional center-weighted metering modes. Exposure compensation of 1/3 steps in a range of ± 3EV is possible. When you want to meter a particular exposure, retain it and then recompose the image; simply push in a small ML (Memory Lock) button conveniently positioned below the LCD panel to hold that setting.

The camera's body is made of aluminum protected by a glass-fiber reinforced polycarbonate coating which is thicker than normal to provide more shock and wear resistance. All existing SMC Pentax-A 645 lenses can also be used with the new 645N camera without any modification--except they will not be capable of autofocusing. There are five brand new SMC Pentax FA autofocusing lenses designed specifically for this AF camera.

A flat prism gives a bright, right-side-up image with full data about the exposure visible on an LED just below the image area of the viewfinder. Data shown is the shutter speed; aperture; flash status; in-focus indicator; exposure indication; and a bar graph (used for exposure compensation or metered manual). The brightness of the LCD data is automatically adjusted according to the subject's illumination level. In the center of the natural-bright matte focusing screen is a circle for spot metering and two bracket marks indicating the three-point AF frame. Optional screens include AF split image, AF microprism, or cross-lined matte. The eyepiece has a built-in diopter adjustment with a range of -3.5 to +1.

Strong late afternoon sunlight brought out the color and texture of the large leaves on this new tree growing in our front yard. Keeping the background in the shade and drastically out of focus placed the emphasis on the central leaves. (Kodak Ektachrome E100SW, 75mm 1/90 at f/4, spot metering.)

Logically clustered around two primary control large dials on either side of the prism eyepiece are most of the optional controls. The shutter speed dial to the right of the viewfinder securely locks into the green "A" Automatic or orange "X" flash synch setting. To make any change from either of these two primary settings a button in the center of the dial must first be pressed in before a change can be made. Thus you cannot accidentally change the shutter speed easily. When set for any of the remaining speeds of 4 sec to 1/1000 sec or Bulb there is just a positive detent to hold the actual shutter speed selected. Just below this dial is the switch for selecting any of the three metering methods with the primary multi-segment metering marked in green for easier locating.

The other large dial on the left controls the exposure compensation while below it is a lever which in one direction permits changing the ISO film speed while in the other direction sets the automatic bracketing for "0", 1/3, 2/3, or one stop increments. The shutter release is located in the front top of the grip and it even has a tapered thread for a cable release, something you don't see often today. Around the release is a rotary lever used to choose the desired drive mode or the self-timer. Just behind the LCD panel is the primary on/off switch while at the end are found triangular up/down buttons used primarily for adjusting the ISO speed but they are also needed when canceling the data imprint function. Along the top rear of the body are found the Servo/Single AF mode selector switch and the AF frame selector switch.

At the front of the body is the lens release button and just above it is a handy depth of field preview lever. On the left side of the body is a second tripod socket (to hold the camera for vertical compositions), a multiple exposure switch, and a covered X-synch PC terminal socket. On the base is the primary tripod socket and a covered external power terminal plus a small button which will wind up the remaining exposures. Concealed under a flap is a terminal for connecting an electronic shutter release cord. To disengage the autofocusing, simply slide a control on any Pentax FA lens from AF to M. In manual focus mode you can visually determine the focus on the ground glass or check when the AF symbol visible in the viewfinder is illuminated.

The film holder has a flip-up, rotary lever which loos-ens the magazine, but to actually remove the holder this lever must be turned a bit further past the stop position to permit lifting it out of the camera body recess. A light-tight protective housing comes with the film holder, which serves as a carrying unit when extra holders are pre-loaded with film for faster changing. Since the film holder completely recesses into the body of the camera, a Polaroid back cannot be used with this camera.

A relatively small yet legible LCD panel on the top shoulder of the body includes a frame counter (that conveniently remains visible even when the power is switched off); ISO film speed information; film status (blank or END); battery level indicator; and imprinting exposure data icon (on or off).

Practical Use Testing. The camera handles surprisingly easy considering it's bulkier and heavier than most top models of 35mm AF SLR cameras. Sure, it's a bit heavier, but not excessively so and it balances very well. The built-in grip (which encloses the six AA size batteries) makes it convenient to grip tightly with your right hand as you support the broad, flat base with your left hand. The controls are well marked, logically located, and easy to operate when you decide to shift from full automatic operation or deviate from neutral normal settings.
I found the camera's autofocusing was very accurate and precise, functioning equally well on vertical and horizontal textures in all types of lighting, and that's all you should really expect from this advanced type of automation feature. Unlike many 35mm AF cameras, there is no focus assist light on the camera body, but it accomplished the autofocusing rapidly and accurately even under dim indoor lighting with dark subjects, so the light did not seem to be needed. There is a focus assist light on the shoe mount flash units since they often might be used under even dimmer light conditions.

I particularly liked the automatic three frame bracketing feature which you can easily switch on or off by moving one lever at the left of the prism. I found all three modes of the TTL metering (six segment, center-weighted, and spot) to be very precise and accurate, but even so, there are still some situations when you might want to bracket exposures (especially on critical color slide film) to be certain one is exactly as you envisioned. You can select increments of 1/3, 2/3, or one full stop bracketing whenever you encounter especially difficult lighting and you want to be absolutely certain you expose the subject properly on at least one frame.

For testing we had a Pentax 645N camera; SMC Pentax-FA 645 75mm f/2.8 normal lens; SMC Pentax-FA 645 400mm f/5.6 ED [IF] Internal Focusing telephoto; and a Pentax AF-330 FTZ TTL dedicated flash unit. There were five new SMC-Pentax FA lenses introduced along with this new autofocusing camera. They are: 75mm f/2.8 (normal) focusing to 2'; zoom 45-85mm f/4.5 focusing to 1.6'; 45mm f/2.8 focusing to 1.5'; 300mm f/4 ED [IF] focusing to 9.8'; and 400mm f/5.6 ED [IF] focusing to 9.8'. Three additional new AF 645 lenses were just introduced at the '99 PMA trade show. SMC Pentax-FA 645 200mm f/4 [IF]; 80-160mm f/4.5 zoom; and the 645 Macro 120mm f/4. All of these new FA lenses feature fully automatic diaphragm control and TTL open aperture metering. The Extra-low Dispersion (ED) optical elements and [IF] mechanism on the telephoto lenses are said to produce crisp images with minimal chromatic aberration and retain a good weight balance due to the internal focusing.

I liked the fact that the LCD panel constantly shows the next frame number so you can check to determine how many exposures are left even when the camera power is switched off. As would be expected on a professional camera, the 645N not only has a dedicated hot shoe on top but there is a PC contact hidden under a cover on the upper left side of the body. A camera of this caliber will often be used with studio AC powered flash units so the PC contact is imperative. Of course the TTL flash metering does not function when the PC contact is used, but most pros will be using a flash meter to determine exposure in any type of studio situation.

During my several months of testing the Pentax 645N I exposed 10 rolls of E-6 color transparency films. They consisted of Fujichrome 100D, Fuji Velvia, Kodak Ektachrome 64X, and Ektachrome E100SW. This type of slow speed film was used exclusively since it shows the capability of the metering best and has the finest grain for checking resolution and sharpness. The transparency films were all processed at Accu-Color Labs., Inc., Fort Wayne, Indiana.

I was particularly impressed with the accuracy of the TTL exposure metering in all three modes. A diverse variety of lighting situations were metered in each of the dual six segment, center-weighted, and spot modes and each exposure was exactly as I would have wanted. Harsh, bright, fall sunlight was the dominant type of lighting for my outdoor testing which was positioned in every compass direction possible to check the metering when the light was primarily side or backlighting in addition to conventional front lighting. Even having lots of deep shadows surrounding small brightly illuminated fall leaves did not fool the sophisticated TTL metering. The resulting images were sharply detailed, crisply focused, and had right-on exposures. Naturally, I also tried the automatic exposure bracketing, primarily on extreme backlit subjects, but found the first "normal" exposure was generally the best of the three bracketed exposures even when lighting was difficult to meter.

The Pentax AF-330 FTZ TTL hot shoe mount dedicated flash unit automatically coupled and dedicated with the camera perfectly giving excellent main exposure lighting in dim situations when it was the dominant light source. In addition, when used for flash fill on severely backlit outdoor sunlight situations once again it coupled with the TTL metering resulting in just the right level of fill flash coming from the camera to balance with the prevailing light conditions.

As usual, I shot part of a roll of a brick wall while the camera was held steady on a heavy tripod to roughly check the lens capability. I don't believe I have ever seen straighter edge lines without any hint of bowing out or in (barrel or pincushion) distortion. In addition, the bricks were exceptionally crisp and sharply detailed from the corners to the center of the image.

The size and weight of the camera are as suitable for easy handheld operation as that of a large pro model 35mm SLR. The balance and handling were excellent. The viewfinder was bright and pertinent exposure data located along the bottom below the image was very legible. It was easy to adjust and operate in all modes. If your photographic endeavors require working with a larger format rollfilm camera that produces images nearly three times larger than conventional 35mm film, then it should be seriously considered. It should be a capable performer in the hands of any serious photographer no matter what type of subject they record on, any type of 120 or 220 format roll film.

The suggested list prices for this equipment are: Pentax 645N camera body $3190; SMC Pentax-FA 645 75mm f/2.8 normal lens $735; SMC Pentax-FA 645 400mm f/5.6 ED [IF] telephoto lens $3414. The TTL metering prism is built into the camera. In addition to the lenses and dedicated flash units there are many other accessories offered for this camera system.

Contact: Pentax Corp., 35 Inver-ness Dr. E Englewood, CO 80155; (303) 799-8000; fax: (303) 790-1131; or on the web at:

Technical Specifications

Type: 6x4.5 format autofocus SLR camera with multimode TTL autoexposure control
Film: 120 roll film; 220 roll film; and 70mm film; film loaded into interchangeable film holder
Image Size: 56x41.5mm
Lens Mount: Pentax 645 AF mount (interchangeable with 645 A mount)
Applicable Lenses: SMC Pentax 645-FA; SMC Pentax-A (usable in manual focus mode only)
Exposure Control: Metering system: TTL open aperture multi-pattern metering
Metering Modes: Dual six segment; center-weighted; spot
Metering Range: EV2-21 (at ISO 100 with 75mm f/2.8 lens)
Exposure Modes: Programmed AE; shutter priority AE; aperture priority AE; metered manual; Bulb
Memory Lock: Activated with ML button; exposure value held for approximately 10 sec
Exposure Compensation: ±3EV (1/3 EV steps)
Shutter: Electronically controlled vertical-run cloth focal plane shutter. Speed: Auto: 1/1000-30 sec stepless; Manual: 1/1000-4 sec; X-synch: 1/60 sec; Bulb.
Viewfinder: Keplerian telescope viewfinder with interchangeable natural-bright matte focusing screen; AF center spot matte screen is standard
Field of View: 92 percent vertical, 93 percent horizontal
Magnification: 0.76x (with 75mm lens at infinity with -1 diopter)
Diopter Adjustment Range: -3.5 to +1.0 diopters
External LCD Indicator: ISO film speed; exposure count; film transport status; battery level; photographic data imprinting mode
Film Advance Modes: Single frame advance; consecutive advance (approx. 2 fps)
Autofocus: Type TTL phase matching autofocus system with focus lock and predictive autofocus
Autofocus Frame: Three point AF; spot AF; PCV beep sound for in-focus indicator can be cancelled
Flash Synchronization: Hot shoe X-synch contact and dedicated flash; X-synch speed 1/60 sec automatically set with dedicated flash unit; speeds slower than 1/60 can be used in shutter-priority AE and metered manual; PC synch contact on left side of body
Photographic Data Imprinting: Seven segment dot matrix data imprinting system; data out of image area
Recordable Data: Exposure frame number; exposure mode; shutter speed; aperture; exposure compensation value; metering mode; lens focal length (if using SMC Pentax-FA lenses, approximate value shown for zoom lenses); data imprinting cancellation available
Self-Timer: Electronically controlled with 12 sec delay
Film Speed: ISO 6-6400
Power Source: Six AA size batteries (alkaline or lithium); battery life approximately 130 rolls of 120 film or approximately 100 rolls of 220 film
Multiple Exposure: Via multi-exposure switch
Dimensions: 5.9x4.4x4.6"
Weight: 45.2 oz (without batteries)