Panasonic GX7 Image Quality
Saturation & Hue Accuracy
Slightly lower-than-average mean saturation levels, with average hue accuracy.
|In the diagram above, the squares show the original color, and the circles show the color that the camera captured. More saturated colors are located toward the periphery of the graph. Hue changes as you travel around the center. Thus, hue-accurate, highly saturated colors appear as lines radiating from the center. Mouse over the links to compare results at different ISOs.|
Skin tones. Here, the Panasonic GX7 does fairly well, producing natural-looking Caucasian skin tones with a slight push towards pink when either Auto or Manual white balance is used, giving a healthy appearance. Darker skin tones have a small nudge towards orange, but overall results are pretty good. 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 Panasonic GX7 shifts orange toward yellow and cyan toward blue, but most other hue shifts are quite minor. The typical yellow to green shift and desaturation is still present, though not as pronounced as some prior Panasonic models. The GX7's mean "delta-C" color error after correction for saturation is 4.91 for JPEGs at the base ISO of 200 (125 is an extended ISO). That's about average these days, and color error remains fairly stable throughout the ISO range, rising just slightly with ISO. Hue is "what color" the color is.
The Panasonic GX7 lets you adjust image saturation in eleven steps each, giving unusually fine control over the effect. The saturation setting also has little effect on contrast, which is good.
|Saturation Adjustment Examples|
The table above shows results with the default as well as the two "extreme" saturation settings. Click on any thumbnail above, then click again to see the full-sized image.
|See full set of test images with explanations
See thumbnails of all test and gallery images
Exposure and White Balance
Indoors, incandescent lighting
Warm colors with Auto and Incandescent white balance setting. Best color balance with the Manual setting, a little cool with 2,600 Kelvin. Average positive exposure compensation required.
|Auto White Balance
|Incandescent White Balance
|Manual White Balance
Indoors, under normal incandescent lighting, color balance is quite warm with the Auto white balance setting. Results with the Incandescent setting are also much too warm, with a slightly stronger orange-yellow cast. The Manual setting produced very accurate results, while the 2,600 Kelvin setting which should match the color temperature of our lights is a bit too cool with a very slight bluish cast. The Panasonic GX7 required +0.3 EV exposure compensation here, about average for this shot. (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.)
Slightly cool colors overall, with a tendency toward high contrast under harsh lighting. About average exposure accuracy.
|Auto White Balance,
|Auto White Balance,
Outdoors, the Panasonic GX7 performed well, with good though slightly cool color in the Far-field shot. Skintones are fairly 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 about average, as the camera required +0.7 EV compensation for our "Sunlit" Portrait shot to keep facial tones reasonably bright. That's about average for this shot. Despite the bright appearance, very few highlights were actually blown in the mannequin's white shirt which is excellent, though there are some very deep shadows. The default exposure is a bit dim for the Far-field shot, but as a result there are no blown highlights, though there are some very deep shadows that are a bit noisy and posterized. Default contrast is on the high side, but that's how most consumers prefer their photos.
Very high resolution, ~ 2,300 lines of strong detail.
|Strong detail to
~2,300 lines horizontal
|Strong detail to
~2,300 lines vertical
|Strong detail to
~2,300 lines horizontal
ACR converted raw
|Strong detail to
~2,300 lines vertical
ACR converted raw
In camera JPEGs, our laboratory resolution chart reveal sharp, distinct line patterns to about 2,300 lines per picture height horizontally, and about 2,300 lines in the vertical direction. (Some might argue for higher, but aliasing artifacts begin to appear before that.) Complete extinction of the pattern occured just after 2,800 lines both horizontally and vertically. We weren't able to extract significantly more high-contrast resolution by processing the Panasonic GX7's RW2 file using Adobe Camera Raw, and the ACR conversion also shows some color moiré which is practically nonexistent in the camera JPEG.
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.
Sharpness & Detail
Very good sharpness overall, with just minor edge-enhancement artifacts on high-contrast subjects. Mild to moderate noise suppression visible in the shadows even at base ISO.
|Very good definition of high-contrast
elements, with just slightly visible
|Subtle detail: Hair
Noise suppression tends to blur
detail in areas of subtle contrast.
Sharpness. The Panasonic GX7 captures sharp, detailed images overall. Some minor edge enhancement artifacts are visible on high-contrast subjects such as the "halos" along the thicker branches and pine cones in the crop above left, but default sharpening here is fairly conservative compared to some consumer-oriented models. 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 effect of noise suppression in the form of smudging of individual strands together in the darker areas of the model's hair, as well as in areas with low local contrast. Still, this is pretty good noise versus detail processing performance for a 16-megapixel Micro Four Thirds model, leaving plenty of detail intact instead of blurring much of it away in an attempt to hide noise. 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.
RAW vs In-Camera JPEGs
As noted above, the Panasonic GX7 produces sharp in-camera JPEGs with good detail. As is almost always the case, quite a bit more detail can be obtained from carefully processing RAW files than can be seen in the in-camera JPEGs, with fewer sharpening artifacts to boot. Take a look below, to see what we mean:
In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking on the link will load the full resolution image.
The first crop from the left is from an in-camera Fine JPEG at default settings. The second is a raw file converted with SilkyPix 3.1 SE (the converter/editor Panasonic bundles with their RAW-capable cameras), using default settings. The third crop is also a RAW conversion done with SilkyPix but with noise reduction and sharpening set as low as they go within the editor, and then sharpened using SilkyPix's output unsharp masking feature set to 350%, a radius of 0.3 pixels, and a threshold of 0. Adobe Camera Raw 8.2 was used for the ACR conversion at right. Default settings were used for conversion, though no sharpening was applied in ACR. The image was then sharpened in Photoshop using the same sharpening settings as we used with SilkyPix.
As you can see, the in-camera JPEG contains pretty good fine detail. SilkyPix however had trouble with the pine needles, flattening them out and making them look reminiscent of a watercolor painting when viewed up close. It's likely doing some fairly heavy-handed noise reduction under the hood which can't be disabled. The results we got using SilkyPix are a bit disappointing, but we must confess we didn't experiment with different settings for very long, so you may be able to do better. The ACR conversion extracted the most detail, but also shows more noise, especially in areas with little detail such as the sky. You can always turn up the luminance noise reduction (default of zero was used here), or process the files in your favorite noise reduction program or plugin if you find the noise objectionable. Bottom line, though, as is usually the case shooting in RAW mode provides better detail, color, and control than in-camera JPEGs when using a good converter.
ISO & Noise Performance
Excellent high ISO performance for a Micro Four Thirds model.
Default Noise Reduction
|ISO 125||ISO 200||ISO 400|
|ISO 800||ISO 1,600||ISO 3,200|
|ISO 6,400||ISO 12,800||ISO 25,600|
The Panasonic GX7's images are very detailed and clean at ISOs 125 (extended) and 200, with only minor luminance and chrominance noise detectable in the shadows. ISO 400 is also quite detailed, though a touch more noise can be seen. ISO 800 shows stronger noise reduction blurring some very fine detail in the process, though overall detail remains very good. ISO 1,600 is of course a little noisier, but fine detail still pretty good. What looks to be a sudden increase in sharpening likely to make up for stronger noise reduction makes luminance noise more obvious with a bit of a crystalline peppered effect at ISO 3,200. At ISO 6,400 and above, the crystalline effect becomes progressively stronger while fine detail is reduced to the point where very little fine detail is left at ISO 25,600. Chroma noise also becomes progressively stronger and objectionable at ISO 6,400 and above.
Overall, though, high ISO performance is excellent for a Micro Four Thirds model, with a noticeable improvement over the GX1, particularly in JPEGs. Although Panasonic leaves a little more noise in GX7 JPEGs than Olympus does, we'd say high ISO performance is very similar to class-leading MFT models such as the E-M1 when comparing RAW files. 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, usually using one of three very sharp reference lenses (70mm Sigma f/2.8 macro for most cameras, 60mm f/2.8 Nikkor macro for Nikon bodies without a drive motor, and Olympus Zuiko 50mm f/2.0 for Four Thirds and Micro Four Thirds bodies). 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
Somewhat high default contrast but with good dynamic range. Very good low-light performance.
|+0.3 EV||+0.7 EV||+1.0 EV|
Sunlight. The Panasonic GX7 did well with the deliberately harsh lighting of this test. Contrast is a little high at its default setting, but dynamic range is good. We felt the +0.7 EV exposure is the best compromise here. Although skin tones around the eyes are a bit dark, we prefer it to the +1.0 EV exposure overall, because there are very few clipped highlights. It's really the photographer's choice here as to which direction to go in. For those Panasonic GX7 owners that are going to want to just print an image with little or no tweaking, the +1.0 image would probably produce a better-looking face uncorrected. The bottom line though, is that the Panasonic GX7 performed well with the wide dynamic range of this shot, better than prior models.
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.)
Dynamic Range Analysis
A key parameter in a digital camera is its Dynamic Range, the range of brightness that can be faithfully recorded. At the upper end of the tonal scale, dynamic range is dictated by the point at which the RGB data "saturates" at values of 255, 255, 255. At the lower end of the tonal scale, dynamic range is determined by the point at which there ceases to be any useful difference between adjacent tonal steps. Note the use of the qualifier "useful" in there: While it's tempting to evaluate dynamic range as the maximum number of tonal steps that can be discerned at all, that measure of dynamic range has very little relevance to real-world photography. What we care about as photographers is how much detail we can pull out of the shadows before image noise becomes too objectionable. This, of course, is a very subjective matter, and will vary with the application and even the subject matter in question. (Noise will be much more visible in subjects with large areas of flat tints and subtle shading than it would in subjects with strong, highly contrasting surface texture.)
What makes most sense then, is to specify useful dynamic range in terms of the point at which image noise reaches some agreed-upon threshold. To this end, Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. The noise thresholds are specified in terms of f-stops of equivalent luminance variation in the final image file, and dynamic range is computed for noise thresholds of 1.0 (low image quality), 0.5 (medium image quality), 0.25 (medium-high image quality) and 0.1 (high image quality). For most photographers and most applications, the noise thresholds of 0.5 and 0.25 f-stops are probably the most relevant to the production of acceptable-quality finished images, but many noise-sensitive shooters will insist on the 0.1 f-stop limit for their most critical work. A full discussion of all the data Imatest produces is really beyond the scope of this review: Visit the Imatest website for details of what the program measures, how it performs its computations, and how to interpret its output.
JPEG. The graph at right (click for a larger version) was generated using Imatest's dynamic range analysis for an in-camera Panasonic GX7 JPEG file with a nominally-exposed density step target (Stouffer 4110). At default settings and native base ISO of 200, the results show 10.1 f-stops of total dynamic range and that score remains all the way to the "High" quality level. From the chart in the top left, we can see roll-off at the highlight end of the tone curve is gradual, but for shadows it isn't as well-behaved with abrupt clipping to black as well as steps which are spaced apart, which could lead to some visible gradation in very deep shadows. Still, these scores are actually pretty good for a Micro Four Thirds model, and an improvement over the GX1 at the Medium through High Quality levels. Note, that this measurement has a margin of error of about 1/3 f-stop, so differences of less than 0.33 can be ignored when comparing results to other models.
RAW. The graph at right is from the same Stouffer 4110 stepchart image captured as a raw (.RW2) file, processed with Adobe Camera Raw using the Auto setting, then tweaked from there for best results. As can be seen, the score at the highest quality level decreased significantly compared to the in-camera JPEG, from 10.1 to 7.32 f-stops, though total dynamic range increased from 10.1 to 13.2 f-stops with a much better behaved tonal curve at the shadow end. The results here are very good for a Micro Four Thirds model and much better than the GX1 which had roughly the same score at the highest quality level, but much lower scores at lower quality levels. It's worth noting here is that ACR's default noise reduction settings reduced overall noise somewhat (see the plot in the lower left-hand corner) relative to the levels in the in-camera JPEG, which would tend to boost the dynamic range numbers for the higher quality thresholds.
The camera's contrast adjustment was at least some help in handling the harsh lighting.
|Contrast set to lowest,
|Contrast set to lowest,
The Panasonic GX7's lowest contrast setting does a good job bringing out detail in the shadows and darker midtones, but it does little did little to preserve clipped highlight detail in the "Sunlit" Portrait shot. (The default Far-field shot had few highlights clipped to begin with.) Overall, pretty good performance.
|Contrast Adjustment Examples|
Like saturation, the Panasonic GX7 offers 11(!) contrast settings, providing more than the usual latitude in this adjustment. The table above shows results with the default as well as the two "extreme" contrast settings. Click on any thumbnail above, then click again to see the full-sized image.
|Aperture Priority, 0 EV, f/8
Face Detection Off
|Aperture Priority, 0 EV, f/8
Face Detection On
|iAuto, 0 EV, f/2.5|
Like most cameras these days, the Panasonic GX7 has the ability to detect faces (up to 15 in a scene), and adjust exposure and focus accordingly. As you can see from the examples above, face detection improved exposure in both Aperture Priority at f/8, and in iAuto mode where the camera had control over aperture, and automatically applied Intelligent D-Range.
Panasonic's Intelligent Dynamic Range
The above shots are examples of Panasonic's Intelligent Dynamic Range Control (or iD-Range) at work, with no exposure compensation. Note that the camera does not take multiple shots and merge them as HDR mode does (see below). It's a system that adjusts local contrast and exposure more akin to Nikon's Active D-lighting, Canon's Automatic Lighting Optimization or Sony's Dynamic Range Optimization.
There are three levels of iD-Range available on the Panasonic GX7: Low, Standard and High, plus Auto and Off. It's automatically invoked in iAuto and some scene modes and manually selectable in PASM modes. Here, you can see darker midtones and shadows were progressively boosted as the strength was increased, without blowing many highlights in the process. Nice.
Far-field HDR Examples
Here, you can see the Panasonic GX7's High Dynamic Range mode at work with our Far-field shot. HDR mode takes three images at different exposures and combines them to increase dynamic range. Mouse over the links, and click on them the view the full resolution files. We liked Auto and +/-1 the best for this scene, as higher settings didn't work very well with +/-2 actually making shadows a bit darker and +/-3 dimming the entire image. Notice the double images and ghosting of objects or people moving between frames. Also notice the angle of view is narrower in the HDR images, likely because the images have been cropped and upsized during the optional auto alignment process.
Low Light. The Panasonic Lumix DMC-GX7 performed well in our low light tests, able to capture bright images down to the lowest light level we test at, at all ISO settings. The darkest level equates to about 1/16 the brightness of average city street lighting at night, so the Panasonic GX7 should be able to take well-exposed photos in almost any environment in which you can see well enough to walk around in.
Using default noise reduction setting, noise is well-controlled up to ISO 6,400. We didn't notice any significant issues with hot pixels, banding (pattern noise) or heat blooming.
Automatic color balance was a little cool particularly at lower light levels, but not bad.
The camera's 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 (albeit with some hunting), which is excellent, especially for a camera with contrast-detect autofocus. The Panasonic GX7 does have a focus-assist light option which allows it to autofocus in total darkness, as long as the subject is within range and has sufficient contrast.
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.) Thanks to their phase-detect AF systems, digital SLRs tend to do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects. The GX7 uses contrast-detect autofocus, as is found in most point & shoot cameras, so its low-light focusing ability may be less than that of some SLRs with phase-detect systems. That said, though, the larger, more sensitive pixels of the GX7's sensor do better under dim lighting than do the tiny pixels of most point & shoots, (A useful trick is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don't have a tripod handy.)
Very good 24 x 36 inch prints at ISO 125/200; a nice 13 x 19 at ISO 1600; a good 4 x 6 at ISO 12,800.
ISO 400 shots look quite good at 20 x 30 inches, with good sharpness in finely detailed areas.
ISO 800 prints look good at 16 x 20 inches. As is the case with most cameras in this class, subtle contrast detail is starting to fade by this ISO setting in our tricky target red swatch, but still makes for a good overall print.
ISO 1,600 makes a nice 13 x 19 inch print, with only mild softening in the red channel.
ISO 3,200 tends to be the turning point for most Four Thirds sensored cameras, as is the case here, and requires a reduction to 8 x 10 inches due mostly to noise in flatter areas.
ISO 6,400 prints have enough detail for a decent 8 x 10 inch prints for less critical applications, and a 5 x 7 inch print for our official "good" rating.
ISO 12,800 yields a good 4 x 6 for this ISO and sensor type.
ISO 25,600 prints at 4 x 6 are a bit too watercolored looking to make our "good" standard, but still retain full color and would be usable for many less critical applications.
The Panasonic GX7 stands its ground in the print quality department, besting its predecessor the GX1 by a print size across many of the available ISO settings, and performing fairly well as compared to many of its competitors. 24 x 36 inch images at ISOs 125 and 200 are quite sharp, and yet it's nice to know that you can print a reasonable 4 x 6 for the relatives even at ISO 12,800.
Testing hundreds of digital cameras, we've found that you can only tell just so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon Pro9000 Mark II studio printer, and on the Canon Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)