White Balance

The Z750 has fairly comprehensive white balance controls, with six presets (daylight, cloudy, shade, fluorescent 1 and 2, incandescent) and one manual (custom) setting in addiition to the default Auto mode. In our tests outdoor white balance was excellent, very difficult to fool. Indoors the results below pretty much reflect our real-world findings; not to much trouble with fluorescents but a distinct warm tone to shots under incandescent (tungsten) lighting (though the Incandescent preset produces perfectly neutral results). Interestingly the Z750 is the only camera I think I've ever seen that allows you to change the white balance setting on a JPEG image after it has been saved. Unlike similar options for RAW files, however, this feature applies a color correction to the saved JPEG, and so can only work with the processed data. The results vary from very impressive (when the white balance of the saved file is only slightly wrong) to almost pointless (it cannot return an orange-tinted incandescent shot to anything approaching normality), but it's a novel feature in a camera loaded with them.

Outdoor - Auto WB
Red -1.5%, Blue 0.1%

Fluorescent - Auto WB
Red 1.9%, Blue -0.5%
Incandescent - Auto WB
Red 6.1%, Blue -11.0%

Flash Performance

Of all the Z750's features the flash performance is by far the most disappointing. Color is fine (there is a slight tendency to warm skin tones, but this is generally considered a good thing), but the output is so pitifully low that - even with the ISO set to auto (which maxes out at ISO 200) - you have to be very careful if you want to avoid completely underexposed (and very noisy) flash shots. Our skin tone test had to be shot at wideangle (we'd normally zoom in) as we couldn't get a bright enough result at the 5 feet or so away you need to be to get the head and shoulders into the frame. If you use flash a lot then you need to be aware that the results will be fine if your subject is close, but not if they're more than a couple of metres away. We also found red-eye to be a real problem in most shots. When shooting within the flash range both exposure and color are very reliable, and focus - in very low light - excellent at distances up to about 1.0m, thanks to the AF illuminator.

Skin tone
Slight warm tone, well exposed
Color chart
Excellent color,good exposure

Macro Focus

The Z750 has a dedicated macro mode that works at all focal lengths, but - as is normal in cameras such as this - is most effective towards the wide end of the zoom. This provides a minimum focus distance of around 10cm giving you an area of just under 8cm across to work with - hardly class-leading but fine for occasional close-up snaps. Inevitably there is some distortion at the wide end of the zoom, but it's not too strong (mainly because compared to many of its competitors, the Z750's macro mode doesn't actually allow you to get very close). There is also a little Chromatic Abberation (CA) visible towards the edges of the frame in macro mode (this is much harder to see in 'normal' shots).

Wide macro - 79 x 53 coverage
39 px/mm (980 px/in)
Distortion: Average
Corner softness: Average
Equiv. focal length: 38 mm
Tele macro - 109 x 72 coverage
28 px/mm (713 px/in)
Distortion: Average
Corner softness: Average
Equiv. focal length: 114 mm

Barrel and Pincushion Distortion

Whilst there is measurable distortion at the wide end of the zoom (around 1.1%), it is no worse than most compact 3x zooms. It certainly doesn't have a significant impact on real-world shots. Edge sharpness is actually pretty good for a camera in this class and there is barely noticeable (0.3%) barrel distortion at the long (114mm equiv.) end of the zoom range.

Barrel distortion - 1.1% at Wide angle
Equiv. focal length: 38 mm
Barrel distortion - 0.3% at Telephoto
Equiv. focal length: 114 mm

Noise Comparison

Here for visual comparison are three identical shots taken at 50, 100, 200 and 400 ISO settings in our studio. Although the ISO 50 and 100 results are pretty clean (they have relatively low luminance noise), the effects of noise reduction at ISO 200 are fairly obvious, and at ISO 400 there is a distinctly 'blotchy' appearence to the mid-tones and shadows. Usable, and no worse than most of its competitors, as with all cameras in this class, we'd recommend using the EX-Z750's ISO 400 setting only when you really have to.

ISO 50 100% crop ISO 100 100% crop
ISO 200 100% crop ISO 400 100% crop

Specific Image Quality Issues

With all ultra-compact zoom cameras there is always going to be some compromise between image quality and portability, and the EX-Z750 is no exception. On the positive side exposure and focus are generally very good, though - as with many similar models - there is a tendency for the metering to be fooled by scenes with very high contrast or too much sky, something not helped by the high default contrast (see below). Aside from the slightly higher than average per-channel noise (which produces distinct blotchiness in shadow areas) at higher ISO's and the issues mentioned below, there is little to complain about here.

Contrast, saturation, sharpness

As I worked through the 1000 or so images produced in the process of testing the EX-Z750 I was struck time and again by how 'over the top' the results produced by the default settings are; too contrasty, over-sharpened and with garishly bright colors (if you want to see how garish they can get take a look at this full size image). I was therefore relieved to discover that tweaking the image parameters allows you to produce significantly less processed-looking, more 'photographic' results, especially important if you want to do any post-processing. By turning the three parameters (saturation, contrast and sharpness) down to -1 (something I'd recommend doing pretty much permanently) or even -2, you get results with less visible noise, better dynamic range (highlight retention) and less obvious sharpening halos. Why Casio chose to set the defaults to such an extreme is probably a reflection of their estimation of the potential market for this kind of camera than a desire to produce the most pleasing result. It's a pity, but at least it's a problem you can get around.

100% crop 100% crop 100% crop
Default settings Saturation -1
Contrast -1
Sharpness -1
Saturation -2
Contrast -2
Sharpness -2

Color fringing

Noticeable purple fringing is present to some degree in all shots containing very bright (especially overexposed) areas, and in many shots it's very pronounced. It's not enough to mar shots in most circumstances, but wideangle shots on bright days can produce very strong fringes at the boundaries where bright and dark areas meet. It is considerably worse at the edge of the frame. We also found a little corner softness (also visible in this image), though compared to the Canon SD500, for example, it's not a significant problem.

100% crop 38 mm equiv., F8