Pentax 645Z Exposure

Saturation & Hue Accuracy
Vibrant colors with about average hue accuracy.

Saturation. The Pentax 645Z produces images with fairly high mean saturation levels compared to most cameras at default settings, though that's no surprise from Pentax. The 645Z pushes dark red, dark blues, purples and greens a fair bit and some other colors slightly, but undersaturates aqua and cyan. Mean saturation is 119% (19% oversaturated) at the base ISO of 100, and remains above average across the ISO range, peaking at 122.8% at ISO 12,800. Most consumer digital cameras produce color that's more highly saturated (more intense) than found in the original subjects. This is simply because most people like their color a bit brighter than life.

Skin tones. The Pentax 645Z reproduces realistic Caucasian skin-tones with a nice, healthy-looking pink glow to them, though some darker skin tones have a small nudge towards orange. Still, better than average results here. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc.

Hue. The Pentax 645Z shifts orange toward yellow, yellow toward green, and cyan toward blue moderately, but most other hue shifts are quite minor. The 645Z's mean "delta-C" color error after correction for saturation is 5.59 for JPEGs at the base ISO of 100. That's about average these days, but color error gets worse at high ISOs, with a mean "delta-C" color error reaching as high is 9.01 at maximum ISO. Hue is "what color" the color is.

Exposure and White Balance

Indoors, incandescent lighting
Very warm color with default Auto white balance, but only slightly warm with the Incandescent setting. Very good color balance with the Manual setting. Average exposure compensation required.

Indoors, under normal incandescent lighting, color balance is quite warm with the Auto white balance setting, using the default "Subtle Correction" option (there's also a "Strong Correction" option, however we did not test that). Results with the Incandescent setting are actually pretty good, just ever so slightly warm. The Manual setting produced very good results as well, perhaps just a touch cool. Note that the 645Z also has a Kelvin temperature setting as well as Color Temperature Enhancement (CTE) white balance mode which strongly intensified the orange/yellow cast in our indoor test shot on other Pentax bodies, however we didn't try those options with the Z. The Pentax 645Z required +0.3 EV exposure compensation here, about average for this test scene. (Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.)

Outdoors, daylight
Vibrant if slightly cool colors overall, but with high contrast. Above average exposure accuracy.

Outdoors, the Pentax 645Z performed well, with good though slightly cool color in the Far-field shot (at right). Skin tones are realistic in our "Sunlit" Portrait shot, with a healthy-looking push of pinks and reds which is preferable to too flat or yellow. Exposure accuracy is above average, as the camera required only +0.3 EV compensation for our "Sunlit" Portrait shot to keep facial tones reasonably bright. (+0.7 EV is more typical for this shot). Quite a few highlights are blown in the mannequin's white shirt and flowers, though, and there are some very deep shadows, thanks to high default contrast, however all but the deepest shadows are remarkably clean. The default exposure is slightly hot for the Far-field shot, and as a result there are some blown highlights, though shadow detail is excellent with low noise.

See full set of test images with explanations
See thumbnails of all test and gallery images

Resolution
Extremely high resolution, >4,000 lines of strong detail.

Our laboratory resolution chart reveals sharp, distinct line patterns all the way up to the 4,000 lines per picture height limit of our chart from both in-camera JPEG and ACR converted RAW files, though the in-camera JPEG shows some fairly strong aliasing in the form of luminance moiré starting at about 3,500 lines. The ACR conversion shows some color moiré which is practically nonexistent in the camera JPEG, however the conversion shows less luminance moiré, likely because lighter sharpening was applied. Bottom line, though, these are the highest resolution results we've recorded to date.

Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Slightly aggressive default sharpening with moderate edge-enhancement artifacts around high-contrast subjects. Only mild noise suppression visible in the shadows at base ISO.

Sharpness. The Pentax 645Z captures very sharp image with phenomenal detail, but relatively aggressive default sharpening is applied to in-camera JPEGs. For example, you can see fairly obvious sharpening "halos" along the lines and text in the crop above left. You can always turn down sharpening, though (the 645Z defaults to "Hard"), if you feel it's a bit high, and sometimes what looks like oversharpening on screen looks about right when printed. Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows the fairly light anti-noise processing being applied at base ISO, mostly chroma noise reduction. As you can see, many strands of hair are distinct instead of being blurred by noise or heavy-handed noise reduction. Excellent results here, though you can see that some of the strands exhibit the "jaggies", the result of the lack of an anti-aliasing or optical low-pass filter. Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears.

Aliasing artifacts. As mentioned previously, the Pentax 645Z captures phenomenally detailed and sharp images thanks to its amazing resolution and lack of an optical low pass filter, but that means it's also more susceptible to moiré, "jaggies" and other aliasing artifacts than cameras with an appropriate strength low pass filter.

As you can see in our Still Life shots, both color and luminance moiré patterns can be seen in the Samuel Smith bottle label (at right), and you can see aliasing artifacts in some of our other shots as well.

With the increasing trend of using either a very weak or no optical low pass filter, quite a few cameras produce similar artifacts these days when used with a sharp lens, and the 645Z's JPEG processing engine actually does a pretty good job at suppressing aliasing-related false colors in our Resolution target. But like anti-aliasing processing from other cameras it's not fool proof, and luminance moiré is much more difficult to suppress. That's something to be aware of especially if you shoot a lot of man-made subjects with repeating patterns, such as buildings, fabrics, etc. Techniques than can be used to reduce aliasing include shooting at a smaller aperture so that lens diffraction acts as an anti-alias filter, defocusing slightly, shooting at higher ISOs, and post-processing particularly with RAW files.

RAW vs In-Camera JPEGs
As noted above, the Pentax 645Z produces very sharp in-camera JPEGs with phenomenal detail. As is almost always the case, though, additional detail can be obtained from carefully processing RAW files, with fewer sharpening artifacts to boot. Take a look below to see what we mean:

In the table above, we compare an in-camera, best quality JPEG taken at base ISO using default noise reduction and sharpening (on the left) to a matching RAW file converted with Adobe Camera Raw 8.6 using default noise reduction with some moderate and tight unsharp masking applied in Photoshop (250%, radius of 0.3 pixels, and a threshold of 0).

As you can see, the RAW conversion did indeed extract additional fine detail especially noticeable in the mosaic crop, despite having lower contrast and sharpening applied. You can also see that ACR more accurately rendered the color in our pink fabric, compared to the more magenta tint generated by the camera. Interestingly, there's better contrast in the red-leaf fabric as well. And because the 645Z's files at low ISOs are so clean, noise isn't really anything to be concerned with.

Still, the Pentax 645Z produces amazing JPEGs right out of the camera, though as is usually the case, you can produce even more detail when working with RAW files and a good converter.

ISO & Noise Performance
Excellent high ISO performance up to ISO 6400!

The Pentax 645Z's images are incredibly detailed and clean at ISOs 100 through 400. ISO 800 shows a very slight decline in detail, but it's still amazingly good. Detail very gradually declines between ISO 1600 and 6400, showing slightly higher noise as ISO increases, but ISO 6400 is still excellent with a fine-grained luma noise, and very low chroma noise. ISO 12,800 is noticeably softer with coarser noise in the shadows and a hint of chroma blotching, but results are still quite good. Image quality starts to drop off quickly at higher ISOs, though. ISO 25,600 is soft and speckled, with obvious chroma blotching, and this rapidly becomes worse at ISO 51,200 and above, to the point where ISO 204,800 is so noisy with strong speckling and color shifts that it's not usable. In fact, offering ISOs above ISO 51,200 is just an exercise in specmanship.

Overall, though, excellent high ISO performance, and much better than its predecessor. We're of course pixel-peeping to an extraordinary extent here, since 1:1 images on an LCD screen have little to do with how those same images will appear when printed. See the Print Quality section below for our evaluation of maximum print sizes at each ISO setting.

A note about focus for this shot: We shoot this image at f/4. To insure that the hair detail we use for making critical judgements about camera noise processing and detail rendering is in sharp focus at the relatively wide aperture we're shooting at, the focus target at the center of the scene is on a movable stand. This lets us compensate for front- or back-focus by different camera bodies, even those that lack micro-focus adjustments. This does mean, though, that the focus target itself may appear soft or slightly out of focus for bodies that front- or back-focused with the reference lens. We know this; if you click to view the full-size image for one of these shots and notice that the focus target is fuzzy, you don't need to email and tell us. :-) The focus target position will have been adjusted to insure that the rest of the scene is focused properly.

Extremes: Sunlit, dynamic range and low light tests
High default contrast limits dynamic range in JPEGs. Excellent low-light performance, able to capture and autofocus at the lowest light levels we test at.

Sunlight. The Pentax 645Z struggled a bit with the deliberately harsh lighting of this test when shooting JPEGs. Contrast is quite high at its default setting, limiting dynamic range. We felt the +0.3 EV exposure is the best compromise here. Although skin tones around the eyes are a bit dark, we prefer it to the +0.7 EV exposure overall, because the latter has too many clipped highlights. There are very dark shadows as well, however they are quite clean. Bottom line though, the Pentax 645Z's high default contrast in JPEGs means it struggled with the wide dynamic range of this very harshly lit shot. A conversion of the matching RAW file however revealed excellent dynamic range, with only specular highlights blown and very good shadow detail.

Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here.)

D-Range Settings
The Pentax 645Z offers four Shadow Correction levels (Auto, Low, Medium and High, plus Off) as well as two Highlight Correction levels (Auto and On, plus Off). As the names implies, Shadow Correction works to raise shadow levels while attempting to keep highlights and midtones as they are, and inversely, Highlight Correction attempts to reduce highlights without darkening shadows and midtones. Both can be used simultaneously. See the images below to see their effect on our high-contrast "Sunlit" Portrait test shot.

Mouse over the links to see how the various settings for D-Range affects our "Sunlit" Portrait shot, and click on a link to get to the full-res image. (The effect can be a little subtle in shots like those above, so we decided to use a mouse-over to better show how each setting compares to Off.)

Shadow Correction. Above, we see a gradual lightening of shadows and midtones as the Shadow Correction setting is increased, with only a small impact to highlights except at the High setting where a significant number of highlights are blown. If you look closely at the shadow detail, you will notice a slight increase in noise as the setting is turned higher, but that's to be expected and noise levels are still very low. An ISO of 100 was used for all four settings of Shadow Correction, with no apparent limitations.

Highlight Correction. Highlight Correction works as expected when highlights are blown, toning them down to protect them while keeping shadows and midtones roughly the same. ISO 200 was used here, so noise can be more visible.

We looked into how Highlight Correction (HC) interacts with ISO, and here's what we found: If HC is set to Auto and sensitivity is set to Auto or ISO 200 or higher, and the camera decides that the function is needed, HC will operate. If it does so, ISO is bumped to at least 200 if set to Auto. If ISO is set to 100 manually, HC will never operate (or at least, we couldn't get it to do so, and presume it considers respecting manually-set sensitivity a higher priority than saving highlights) If HC is set to On, ISO 100 can still be dialed in manually, but the HC On option will silently disappear from the menu when you do so, and the On setting you made will change to Off. Once you dial the ISO back up to 200 or higher, your earlier setting is remembered and HC turns back on silently.

Face Detection
Like most cameras these days, the Pentax 645Z has the ability to detect faces in Live View mode and adjust exposure and focus accordingly (no word on the number of faces it can detect in a scene, though). As you can see from the examples above, face detection dramatically improved exposure in Aperture Priority mode at f/8, by automatically reducing the shutter speed from 1/30s to 1/25s to brighten the face (in fact, a bit too bright).

HDR Capture
Like the K-3, the Pentax 645Z features an in-camera High Dynamic Range (HDR) capture mode where the camera takes three images (underexposed, normal, and overexposed) in quick succession and combines them into one image. If performed properly, this method should result in much higher dynamic range, without the additional noise penalty that comes with boosting sensitivity or lightening shadows. (In fact, it can reduce shadow noise by combining shadows from the overexposed shot.)

There are four HDR settings available: Auto, and HDR 1/2/3 providing three blend settings, and each setting has three possible exposure ranges (±1 EV, ±2 EV and ±3 EV with ±2 EV default). There's also an optional Auto Align feature for use when shooting without a tripod, which is enabled by default on the 645Z.

Mouse-over the links above to compare thumbnails, and click on them to access full-resolution versions.

The Auto settings worked reasonably well on our Far-field test shot, reducing highlights and bringing out shadow detail. HDR1 and 2 modes produced relatively realistic images though with an obvious HDR look, but HDR3 resulted in an unnatural, very HDR-ish image with strong halos. As with most HDR systems there is a slight focal-length crop with Auto Align active, and watch out for ghosting that can occur when subjects move between exposures such as the waving flag in some of the above shots.

Like the Pentax K-3, HDR is still supported when shooting the 645Z in RAW mode (in many cameras, the two modes are mutually exclusive), resulting in a RAW file is about three times as large as a standard shot. (The cameras are just bundling the individual captures into one file, to be processed later by Pentax's Digital Camera Utility software which can apparently blend or extract the separate RAW files.)

Dynamic Range Analysis (RAW mode)
While we once performed our own dynamic range measurements based on in-camera JPEGs as well as converted RAW images (when the camera was supported by Adobe Camera Raw), we've switched to using DxO Labs' results from their DxOMark website. As technology advanced, the dynamic range of modern high-end cameras in some cases exceeded the range of the Stouffer T4110 density scale that we used for our own measurements. DxO's approach based on RAW data before demosaicing is also more revealing, because it measures the fundamental dynamic range of the sensor, irrespective of whatever processing is applied to JPEGs, or to RAW data by off-the-shelf conversion software.

In the following, we use DxO's "Print" dynamic range results, which are scaled based on camera resolution. As the name suggests, this scaling corresponds to the situation in which you print at a given size, regardless of how many megapixels the camera might have. (In other words, if you've decided to make a 13x19 inch print, that's the size you're printing, whether the camera's resolution is 16 or 300 megapixels.) For the technically-minded, you can find a discussion of the reasoning behind this here on the DxOMark website. Also note that DxO Labs uses a signal-to-noise (SNR) threshold of 1 when defining the lower boundary of acceptable luminance noise in their dynamic range measurements, which corresponds to the "Low Quality" threshold of the Imatest software we used to use for this measurement.

Here, we compare the Pentax 645Z (in red) to its predecessor, the 40-megapixel 645D (in yellow), and also to the 50-megapixel Hasselblad X1D-50c (in orange) which uses a similar if not identical sensor. You can always compare to other cameras on DxOMark.com.

As you can see from the above graph (click for a larger image), the Pentax 645Z offers markedly better dynamic range across the board than its CCD-based predecessor. Peak dynamic range is over two stops higher at 14.7 EV at base ISO, versus 12.6 EV for the 645D, and the 645Z widens its lead slightly as ISO rises.

The Pentax 645Z and Hasselblad X1D-50c are pretty much neck-and-neck for ISOs in common between them, with the X1D-50c exhibiting just a slight advantage because of its slightly lower ISO sensitivity (peak dynamic range is 14.8 EV, which is a negligible difference).

Bottom line: Excellent dynamic range results from the Pentax 645Z's RAW files. Click here to visit the DxOMark review for the Pentax 645Z for more of their test results and additional comparisons.

Low Light. The Pentax 645Z performed well in our low light tests, able to capture bright images down to the lowest light level we test at, even at the lowest ISO setting. The darkest level equates to about 1/16 the brightness of average city street lighting at night, so the Pentax 645Z should be able to take well-exposed photos in almost any environment in which you can see well enough to walk around in.

Noise is practically nonexistent at ISO 100, and very well-controlled at ISO 3200, even at the lowest light levels. As expected, though, the highest ISO setting of 204,800 is quite noisy.

We didn't notice any significant issues with hot pixels or heat blooming, though horizontal pattern noise is visible at the highest ISO.

Automatic color balance is quite neutral on low light, just a little cool.

The camera's phase-detect autofocus system was able to focus on our subject down to below the 1/16 foot-candle light level unassisted with an f/2.8 lens which is excellent, and down to about 1/8 foot-candle in Live View mode which is very good. Note that Pentax 645Z does not have a built-in focus-assist light, however a mounted flash may provide that functionality.

How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that level should be able to snap good-looking photos of street-lit scenes.

NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) Digital SLRs like the Pentax 645D do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.

Print Quality: Stunning print quality, able to print above 30 x 40 inches to ISO 400; ISO 1600 capable of a very nice 20 x 30; ISO 12,800 prints a good 8 x 10!

ISO 100 through 400 prints look terrific at 30 x 40 inches and higher* with excellent detail and vibrant colors. Print size at these three lower ISOs is only constrained by the 645Z's massive resolution, the highest we've tested thus far.

ISO 800 yields a stunning 24 x 36 inch print: super crisp with excellent colors and virtually no apparent noise. 30 x 40's are fine here for less critical applications as well.

ISO 1600 produces 20 x 30 inch prints that have amazing detail in the mosaic tile area of our test target. The only hint that you're going up in ISO is a slight loss of contrast detail in the tricky red fabric swatch of our target, but this is typical of virtually all cameras (except for a few higher-end Nikons, which tend to handle that area better than others as ISO rises).

ISO 3200 prints a very good 16 x 20 inch print, and this is still quite an impressive feat at this ISO, as very few cameras we've tested can make this claim (the 645D didn't even go to ISO 3200). There is minor noise in the flatter areas of our target, like in the shadows behind the bottles, and most all detail is gone from our red fabric swatch, but otherwise a solid print.

ISO 6400 is where the 645Z touches back down to earth, allowing for a good 11 x 14 inch print. There are only minor issues similar to the ones found on the 16 x 20 at ISO 3200, but yet again still a nice size for this ISO. And the 8 x 10 really pops here and is excellent.

ISO 12,800 yields a very nice 8 x 10 inch print. Detail is now gone from our target red swatch but this is quite common at this ISO and higher. The print retains full color saturation and crisp detail in all other areas and, in fact, is one of the best 8 x 10's we've seen at this ISO to date.

ISO 25,600 yields an 8 x 10 that almost makes our "good" standard, and that would have put it into rare company indeed, as only three other cameras have been awarded with "good" 8 x 10's from our lab (the Nikon D4S and D800/E). The 5 x 7 inch print here is excellent though, with great color and detail for such a high ISO.

ISO 51,200 produces a good 4 x 6 inch print. Only a few cameras we've tested have gone higher than this.

ISO 102,400/204,800 do not yield good prints and these settings are best avoided for any applications.

As we've said on rare occasions with only a few other cameras that have come through our lab, your printer will love you for having a Pentax 645Z. Stunning images at ISO 100-400 limited only by resolution, a very nice 20 x 30 inch print at ISO 1600 (the highest ISO the 645D will allow) and even a really good 8 x 10 inch print at ISO 12,800. This is what you'd call "getting the job done" in the print quality department, and we weren't at all surprised by these results given how much we love the 645D. A solid upgrade, and well-done Pentax.

*[Note: we no longer provide print quality ratings for sizes larger than 30 x 40 inches, as we felt this wasn't particularly meaningful. At low ISOs, print sizes from high-quality cameras are pretty much limited only by their resolution, vs noise and noise-reduction processing. Going forward, we'll simply note "30x40 or larger" for cameras that achieve that level. As we see it, the real challenge comes at higher ISOs, where noise and noise-reduction processing become bigger factors, and maximum sizes would be more representative of sizes a majority of users would actually print at.]