Pentax 645D Review vs. Nikon D3x


On-off buttonThe operation of the 645D is straightforward and you hardly ever have to consult the manual. If you come from a Pentax K-5 or K-7 you will appreciate the similarities, but even if you're unfamiliar with Pentax you will quickly feel at home with the 645D. It has the typical Pentax features such as Hyper Program: you can seamlessly switch between Av and Tv mode, when using P mode. The LCD provides feedback regarding which values can be changed - simply by using the control wheel.

Below we will highlight some of the novel features of the 645D and features that work differently from what you might expect. Therefore we will skip the more mundane features that are common amongst any other camera: EV compensation, ISO setting, optical preview, etc.

Using the Two SD Card Slots

SD Card ButtonsThe 645D has two SD card slots located on the left hand side (when seen from behind). You press one of the SD1/SD2 buttons located left of the viewfinder and then use the rear control wheel to set how you want that card used. If you shoot RAW+ you can use one slot for RAW and the other for JPG, you can use one card first (both file types), then the next, or you can save the files simultaneously to both cards so as to have a backup. The same options apply if you shoot JPG only. It would have been nice when shooting JPG to be able to save two different resolutions to the two cards. However, that is not possible (eg. in full resolution to one card and an image suitable for e-mail/web posting to the second card).

If you have set a slot to JPG then you can use the front control wheel (after pressing the appropriate SD button) to set the quality (one to three stars) and the resolution (L (40MP), M (32 or 21MP) and S (13 or 7MP)). The selection of recorded pixels for M and S is set in a custom function. In other words, the front control wheel cycles through L***, L**, L*, M***, M**, M*, S***, S** and S*. We found this way of setting the format much preferable over traditional menu usage.

The RAW button is used for temporarily changing the file format recorded from, say, JPG to RAW.

Exposure Modes

Exposure Modes

We like that the exposure mode dial has a lock in the middle so as to secure it from being accidentally knocked off its setting. In order to change exposure mode the lock button must be pressed down. This can easily be done with your index finger while you then turn the dial with your thumb and middle finger.

Below the mode knob you find a lever to set the metering pattern (spot, centerweight, and multi-segment).

Exposure Mode

How it Works

P (Hyper Program) This is Pentax's innovative version of program mode, called Hyper Program. The camera sets aperture and shutter speed but you can use the front dial to set the shutter speed yourself and thus instantly be in Tv mode. The shutter speed set will be retained for future shots. The green button brings you back to Program mode. Similarly, the rear control wheel will set the aperture and instantly set Av mode
Sv (Sensitivity Priority) You set the sensitivity (ISO) with the front control wheel, and the camera sets exposure (shutter speed and aperture) to match
Tv (Shutter Priority) The traditional shutter priority mode. You set the shutter speed, the camera sets the matching aperture. If the ISO setting is on Auto then the camera will also adjust the ISO as needed to maintain proper exposure
Av (Aperture Priority) The traditional aperture priority mode. You set the aperture, the camera sets the matching shutter speed. If the ISO setting is on Auto then the camera will also adjust the ISO as needed to maintain proper exposure and maintain a high enough shutter speed for handheld shooting
TAv (Shutter/Aperture Priority) Another Pentax innovation: The camera sets the sensitivity (ISO) to mach the shutter speed and aperture set by the user
M (Hyper Manual) Metered Manual exposure mode. You set shutter speed and aperture like in a traditional M mode with the aid of the camera's meter. Pentax has added a couple of features, hence the term Hyper Manual: (1) Press the green button and the camera will set shutter speed and aperture as per the current program line. You can then adjust exposure from there. (2) Press the AE-lock button. This will lock the exposure at the EV value defined by the shutter speed and aperture you have selected. If you now change, say, the aperture, the camera will change the shutter speed so that the set exposure value is maintained
X (Flash X-synch Speed) Sets the shutter to 1/125 sec for use with non-Pentax flashes which doesn't set the shutter speed automatically
User (User setting) Recalls a previously saved exposure mode and set of exposure settings


AFS AFC SwitchThere is no AF/MF switch on the camera body, you switch between auto focus and manual focus on the lens. There is, however, a knob for switching between single shot auto focus and continuous (tracking) auto focus.

We found it very easy to achieve proper focus manually with our f/2.8 A-series primes and the FA 80-160mm f/4.5 zoom thanks to the large, bright view finder.

Auto focus was fast and accurate with our test lenses, the FA 45mm f/2.8 and FA 80-160mm f/4.5. Both lenses stem from the film era and use the drive shaft auto focus mechanism which does generate some noise during auto focus. Unfortunately, no lenses with built-in auto focus motor ("SDM-lenses") were available to us.

However, if you have the 645D on a tripod like we had most of the time, auto focus is not that useful. The reason is that the 11 auto focus points are clustered in the center of the frame and unless that's were you want to focus you'd have to move the camera so that the AF points cover your main subject, auto focus and lock, and then move the camera back to the position your composition dictates. Clearly the auto focus sensor was lifted from either the K-7 or K-5, where, due to the much smaller image format, the AF points do cover a good deal of the frame. We would have liked to see an AF sensor developed specifically for the 645D and with AF points covering most of the frame so that one could effectively use auto focus with the camera on a tripod.

A look at the focusing screens illustrates the issue:

645D versus K-5 focusing screens

You can let the camera select the auto focus point, you can pick which point to use with the 4-way controller. The latter is almost pointless since the AF points are clustered in the center, so using the center point seems to be the best option.

Mirror-up Shooting

Mirror-up ButtonThere are several ways to achieve mirror-up shooting. The most straight forward way is to turn the mirror lock-up button to the M. UP position. In this position, the first press of the shutter button will flip the mirror up, the next will take the shot (or all shots if exposure bracketing is set). This works similarly with the remote control.

Alternatively, mirror lock-up can be achieved through the drive mode menu shown below.

Drive Mode Menu

The two-second self-timer mode will flip the mirror up and take the shot two seconds later. This process will repeat in case of exposure bracketing (if one-push bracketing is set in the custom menu). The 3 second delay remote operation will also flip the mirror up and then delay for the shot. But curiously enough, in case of exposure bracketing the subsequent shots will be taken with no delay between the raising of the mirror and firing of the shutter. We wonder if this is intentional or an error in the firmware. So if mirror lock-up is desired in connection with the remote control and exposure bracketing, the dedicated mirror up button should be used.

Continuous Shooting

Drive Mode MenuThere is no dedicated button for this. You must hit the drive mode button and navigate to either the continuous shooting mode (second icon from the left) or the remote continuous shooting mode as illustrated to the right.

In the remote continuous shooting mode the first press on the remote starts shooting and the second press stops shooting whereas in the shutter button continuous shooting mode shooting continues only for as long as the shutter button is depressed.

The frame rate is about 1.5 frames per second until the internal buffer is full (about 13 frames RAW and 15 frames JPG). At this point the frame rate depends on the time it takes to write an image to the SD card freeing up buffer space for the next image. We can only recommend that you use the fastest cards available if you're into continuous shooting (like a SanDisk Extreme Pro 45MB/s SDHC card). As a reference we experienced DNG file sizes between 51 MB and 74 MB in size (the size depends on the amount of detail in the image).

Exposure Bracketing

BracketingExposure bracketing is easy to enable and adjust. The 645D has a dedicated button for this. Press it and the front control wheel now controls the number of frames (2, 3 or 5) and the rear control wheel controls the bracketing steps in 1/3 EV steps or 1/2 EV steps where you set your preferred step size in a custom function.

The front wheel operates cleverly like this: Turn it to the right and you can choose between Off, 3, or 5 frames. Turn it left and you can chose between Off, 2 frames with one being underexposed, or 2 frames with one being overexposed.

The bracketing can bee shifted up or down by dialing in EV compensation so that you can achieve for example this bracketing: -1 EV, -0.5 EV, and 0 EV compensation.

All bracketed shots can be taken by one push of the shutter button provided that this is set up in a custom function.

Control Panel and Status Screen

Control PanelMost image parameters can be set through one of the many buttons or dials on the camera body. A few, like HDR shooting, has no dedicated button and is set through the Control Panel, which is called up on the monitor by pressing the Info button. The Control Panel also offers an alternative way of setting some of the parameters which otherwise have a push button.

Status ScreenThe Status Screen shows the most important shooting settings (but doesn't provide for changing the values) and is called up by hitting the Disp button.

Electronic Level DisplayHitting the Disp button a second time brings up the electronic level display which is particularly useful when shooting from a tripod. The screenshot below shows the camera level (green line) but tilted down (yellow bars).

Instant Review

It took longer than we had expect before the image captured would show on the rear monitor. However, turning off histogram and the over/underexposure warnings reduced the time before the image would show to about 1.5 seconds. Depending on your shooting style this could be an issue. We are usually not into "chimping" so the time to review isn't that important to us when first we get to know our camera and lens well. However, with instant review turned off, we had to wait for the image to be written to the card and then be played back when we did want to chimp. This process would take 4 to 5 seconds and that feels like a life time. The 645D would definitely benefit from a faster processor and write speed for the purpose of reviewing the captured images. As it is now it is better to leave Instant Review on for that occasional chimp and just ignore it otherwise.

Flash Photography

The 645D is compatible with all Pentax flashes, past and present. The camera does not support TTL flash photography, so TTL flashes will have to be used in auto or manual mode. The flashes can be mounted in the hot shoe or attached to the hot shoe by a dedicated extension cord.

There is also a standard X-synch contact for connecting a flash. No dedicated functions of the flash are available when connecting via the X-synch contact.

AF540FGZ FlashThe following functions are available with current dedicated flashes like the AF540FGZ and AF360FGZ:

  • P-TTL auto flash
  • external auto flash
  • red-eye reduction
  • automatic setting of the X-synch speed
  • automatic setting of the aperture in P and Tv mode
  • slow-speed synchronization
  • trailing curtain synchronization
  • contrast-control flash
  • slave flash
  • flash exposure compensation
  • AF assist light
  • high-speed flash synchronization
  • wireless flash (two or more flash units are required).

The flash synchronization speed is 1/125 s. A slow synch speed can be an issue in connection with fill flash if a shallow depth of field is desired or in order to avoid overexposure of those parts of the scene illuminated by ambient light. Shallow depth of field calls for a large aperture like f/4 or f/2.8, which then in turn requires a fast shutter speed for correct ambient light exposure. But if the required shutter speed for correct exposure is faster than 1/125 s use of fill flash is not possible.

There are two ways around this limitation:

  1. Use of a natural density (ND) filter. With an appropriate ND filter the shutter speed can be brought down to, or below 1/125s making fill flash possible.
  2. Use of a lens with a built-in leaf shutter. The Pentax leaf shutter lenses have a fastest shutter speed of 1/500s and would in most cases make use of an ND filter superfluous.

Leaf shutter lensTwo leaf shutter lenses were produced for the 645 film cameras and these lenses can be used with the 645D:

With the leaf shutter mode engaged, the 645D will be go into M exposure mode irrespective of the mode set on the dial, and the light meter will not operate. A number of other features will also not be available, hereunder EV compensation, AE lock, continuous shooting, mirror lock up. The flash must be connected to the X-synch contact on the lens for synchronization to work properly. When off leaf shutter mode there are no restrictions, but, since the lens has no "A" setting, P and Tv exposure modes are not supported.

Operation - 645D Contrasted to Nikon D3x

The Nikon operates must faster than the Pentax with a 5 fps frame rate and a very fast processor, which allows for almost instantaneous preview of the captured image. The Nikon has 51 AF points and they are distributed over a sufficiently large part of the frame that tracking a moving object is doable.

Auto focus speed was about the same with the two lenses we used for this test (the FA 45mm F2.8 on the Pentax and the 35mm F1.4 on the Nikon), suggesting that the Pentax FA screw drive auto focus system is on par with modern ultrasonic AF motors in terms of speed.  However, in low-light scenarios, the Nikon was more accurate and as a result focused faster and more reliably (hunted less). This could perhaps to some extent be attributed to the lens being two stops faster.  Regardless, it's clear that the Nikon's AF system is usable for a wider variety of applications.

The Nikon can take up to 9 images during exposure bracketing, the Pentax just 5. However, 5 is more than adequate to compensate for uncertainties as to how to expose for a particular scene. In connection with HDR photography, the Nikon's 9 image capability could come in handy.

Being used to Hyper Program on Pentax we found it frustrating on the Nikon that we had to explicitly switch to or between Av and Tv modes in order to lock in an aperture or shutter speed "on the fly". When it comes to changing shooting settings we find the Pentax more user friendly.

The electronic level on the Pentax is a useful help to level the camera when using it on a tripod. The Nikon has a similar feature, called a virtual horizon, although it only indicates horizontal level, not also forwards/backwards tilt like the Pentax.

The Nikon has a flash synchronization speed of 1/250s. This is, in practice, equivalent to the Pentax's 1/125s since the Nikon has one stop more depth of field than the Pentax at a given aperture, and use of a ND filter could be required to avoid overexosure as explained above for the Pentax. Leaf shutter lenses are not available from Nikon. PentaxForums @PentaxForums News | Reviews | Forum

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