Ricoh GR III Camera Review

Aberrations

No lens can be totally free of optical flaws. The following list describes the main defects that a lens can suffer from.

Name
Description
Chromatic aberration Different colors do not have the same focus point. The result is colored lines (usually red or green) on edges showing a sharp transition from clear to dark tones, and a general decrease of the sharpness. Occurs mostly at wider apertures. Easy to correct via software. Mitigated by the use of achromatic lens elements. In simple terms, lateral CA occurs in the in-focus zones, while longitudinal CA occurs in out-of-focus zones.
Purple fringing Sometimes caused by chromatic aberration effects. Can also occur because the RGB color filters in front of pixels create differences in pixel sensitivities. Creates a purple band on edges showing a sharp transition from clear to dark tones. Occurs mostly at wider apertures. Easy to correct via software.
Flare Internal reflections on the various lens elements cause a decrease of contrast, the apparition of a bright veil, or ghosting. Occurs if an image includes bright light sources, especially if the light source is near the edge. Using a lens hood helps to control flare. Better lens coatings greatly reduce the effect.
Ghosting A type of flare causing artifacts (orbs) to appear on an image including bright light sources, especially if the light source is near the edge. Can be used artistically.
Coma Flaws in the optical design cause point sources (such as stars) located on the sides of the frame to appear elongated. Dependent on the lens design.
Distortion Straight lines appear curved. Dependent on the lens design. Tested in another page.
Spherical aberration Light rays hitting the sides of the lens do not have the same focus point as those passing through the center. Mitigated by the use of aspherical elements.

Not all of those optical effects are easy to test independently. Purple fringing and chromatic aberrations are almost always coupled, and will be tested together. Flare and ghosting will also be measured as a pair. Distortion will get its own page later in this review. The other aberrations will not be formally tested as their effects are both harder to isolate and generally better controlled by design.

Flare

Flare will affect images in which a bright light source, such as the sun, is present in the frame or near its border. The use of a lens hood helps reduce the effect for side lighting, as does a recessed front element. High-quality lens coatings play a very important role in minimizing flare, by improving light transmission and minimizing internal reflections.

The GR III’s lens does not boast the same acronyms as a Pentax lens. Nonetheless, it is a modern design and should offer robust performances.

Flare Test One - Center-of-Frame Sunlit Flare

As usual, we used the sun as our light source for flare testing. It is bright and covers a wider range of wavelengths than most artificial light sources. We offset the sun slightly in order to see eventual ghosting which could be hidden if there was a straight line between the light source and the sensor. You can click on the thumbnails for larger views.

F2.8
F4
F5.6
F8
F11
F16

Flare with the sun in the center is kept tightly under control. The only ghost is a blue spot almost invisible below F5.6, slightly below the sun.

All in all, superb flare control from this lens.

Flare Test Two - Edge of Frame

For this test, we placed the source in the top right corner of the frame, directly illuminating the sensor. You can click on the thumbnails for larger views. 

APS-C

F2.8
F4
F5.6
F8
F11
F16

Regarding flare and ghostings, the images above are perfect. There is literally nothing to see. This is outstanding.

Chromatic Aberration Test

For this test we used a well-lit, sharp transition from dark to bright, in order to make manifest any chromatic aberration present in the image.

We then looked at three parts of the image: the focus point, the top and the bottom (beyond and before the focus point). You can click on the images to see 100% crops, and navigate by using the left-right arrows.

Center
Top
Bottom
F2.8 F2.8 Center F2.8 Top F2.8 Bottom
F4 F4 Center F4 Top F4 Bottom
F5.6 F5.6 Center F5.6 Top F5.6 Bottom
F8 F8 Center F8 Top F8 Bottom
F11 F11 Center F11 Top F11 Bottom
F16 F16 Center F16 Top F16 Bottom

The lens on the GR III shows impressive results for chromatic aberrations. At wider apertures (up to F5.6) there is a small hint of blue-green fringing on the "top" images, and F2.8 hints at some CA at the bottom. The images are devoid of chromatic aberration effects in the center.

Note that the donut-shaped highlights that we mentioned in the Bokeh page are obvious here.

Verdict

Flare is almost perfect with the GR III's lens. There is one small ghost with the sun in the center, and nothing with corner illumination. This is better than could have been expected.

The camera also offers images almost free of chromatic aberrations, except at the very edges of the frame and at wider apertures. This lens is really impressive, in general terms, regarding aberrations.


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