Olympus C-750 Ultra Zoom

Slight greenish color cast and high contrast, but overall results are quite good.

The extreme tonal range of this image makes it a tough shot for many digicams, which is precisely why I set it up this way, and why I shoot it with no fill flash or reflector to open the shadows. The object is to hold both highlight and shadow detail without producing a "flat" picture with muddy colors, and the C-750 Ultra Zoom performed fairly well, but the contrast was a little high, even with the manual contrast-adjust setting dialed down.

The shot at right was taken with a +0.7 EV exposure compensation adjustment, about average for this shot. Contrast is high, which results in a limited midtone range, and some lost detail in the highlights. The camera's Auto white balance setting produced the most accurate color overall, despite a very slight greenish cast. The Daylight setting was a bit magenta, and the Manual setting was warm.

Marti's skin tone looks good (although just a little ruddy in places), and colors in the bouquet look very good as well. The blue flowers in the bouquet are a bit darker than in real life, and the blue has a bit more purple in it than it should, but it's quite close overall. (This is a very difficult blue for many digicams to get right. For reference, the flowers are a light navy blue, with just hints of purple in them.) Resolution is very high, with a lot of fine detail visible throughout the frame, even in the deep shadows. Noise is low in the shadow areas, with a tight grain pattern. Details are also nice and sharp, with good definition throughout the frame. Following is an exposure series, as well as abbreviated contrast and saturation series.

To view the entire exposure series from zero to +1.3 EV with the low contrast setting, see files C75OUTLCAP0.HTM through C75OUTLCAP4.HTM on the thumbnail index page.

Contrast Series:

The C-750's Contrast adjustment does tone down overall contrast somewhat, but I still found contrast a little high, even at the lowest setting.

Contrast Series
-5	+0	+5

Saturation Series:

However, the camera's saturation adjustment does an effective job of controlling saturation, covering a useful range, in fine steps.

Saturation Series
-5	+0	+5

Closer Portrait:

Good color, very high resolution, with sharp detail throughout the frame.

Results are similar to the wider shot above in regards to color cast and overall exposure, and the C-750 Ultra Zoom's 10x zoom lens helps prevent distortion of Marti's features, avoiding the "chipmunk" look common to fixed focal length cameras with wide-angle lenses. Resolution is even higher in this shot, with excellent detail in Marti's hair and face (probably more detail than she'd like ;-). The shot at right was taken with a +0.3 EV exposure compensation adjustment, which brightened up the midtones just a little. As with the wider shot above, contrast is a little high, even with the C750's contrast adjustment dialed down to a low value. Shadow detail is again strong though, with low noise.

To view the entire exposure series from 0 to +1.0 EV, see files C75FACLCP0.HTM through C75FACLCP3.HTM on the thumbnail index page.

Indoor Portrait, Flash:

Normal Flash +0.3 EV

Slow-Sync Mode +0 EV

An excellent performance: Good intensity with the built-in flash, much less exposure compensation required than with most cameras.

The C-750 Ultra Zoom's built-in flash illuminates the subject well, with good overall color. I obtained the best exposure with only a +0.3 EV exposure compensation adjustment, which just verged on blowing the highlights on Marti's white shirt, but left the rest of the image with a very good exposure. (This is quite a bit less exposure compensation than most digicams require for this high-key subject.) The fairly strong incandescent room lighting produces a noticeable orange cast on the back wall, which also spills onto Marti's features. I also shot with the camera's Slow-Sync flash mode setting, which synchronizes the flash with a slower shutter speed for a more even exposure. The best exposure here was obtained with no exposure compensation adjustment at all. Lighting is much more even in this shot, but the room light and flash combine a little oddly to produce a somewhat purplish cast, albeit not a terribly strong one.

Overall, I'd have liked the C750 in flash mode to have picked up less yellow cast from the room lighting, but the result isn't bad, as it faithfully conveys a sense of the warmth of the original scene.

To view the entire exposure series from zero to +1.3 EV with the normal flash mode, see files C75INTFP0.HTM through C75INTFP4.HTM on the thumbnail index page. The slow-sync examples span a range from -0.3 to +1.0 EV, and are found in files C75INTFSM1 through C75INTFSP3.HTM.

Indoor Portrait, No Flash:

Auto White Balance

Incandescent White Balance

Manual White Balance

Good (albeit not stunning) color with all white balance settings.

This shot is always a very tough test of a camera's white balance capability, given the strong, yellowish color cast of the household incandescent bulbs used for the lighting. The C-750 Ultra Zoom's white balance system did pretty well with it, although it left slight color casts with all three white balance settings I tested. I eventually settled on the Incandescent white balance setting, as it seemed the most faithful to the original scene, although it was still a tad warmer-toned than I'd have liked. The Auto setting produced more of a pink cast, and the Manual setting was a touch greenish. Marti's skin tone in the Incandescent shot is a little orange, and the blue flowers are very dark and purplish. The shots at right have a +1.0 EV exposure compensation adjustment, except for the incandescent one, which has +1.3. (+1.3 is the most correct exposure, but I didn't shoot the other white balance settings with that setting, as I only ran the full exposure series with the Incandescent white balance.

To see the entire exposure series from zero through +1.7 EV, see files C75INTP0.HTM through C75INAP5.HTM on the thumbnail index page.

ISO Series:
The C750 seems to have image noise that's a good bit higher than average among four megapixel cameras I've tested. Even at ISO 50, noise is higher than average, although probably acceptable. It increases steadily with increasing ISO, reaching a really objectionable level at ISO 400. You can no doubt use the C750 at ISO 400, but I'd say only as a last resort...

ISO Series
ISO 50	ISO 100	ISO 200	ISO 400

House Shot:

Auto White Balance

Daylight White Balance

Manual White Balance

Slight color casts with all white balance settings, the Daylight option does best, great resolution and detail.

Although slightly warm, the C-750 Ultra Zoom's Daylight white balance setting produced the most accurate color here, with a good white value on the house trim and overall color balance. The Auto and Manual settings produced good results too, but Auto was slightly reddish and Manual a little cool and greenish. Resolution is very high, and the tree limbs and shrubbery show a lot of fine detail. (The C-750 Ultra Zoom's 4.0-megapixel CCD is capable of showing about as much detail as can be found in this poster, even though it was made from a 500MB scan of a 4x5 negative shot with a tack-sharp lens.) Details are sharp throughout most of the frame, with a little softness in the corners that extends down both sides of the frame.

Far-Field Test

Good dynamic range and accurate color, with excellent detail and resolution.

This image is shot at infinity to test far-field lens performance. NOTE that this image cannot be directly compared to the other "house" shot, which is a poster, shot in the studio. The rendering of detail in the poster will be very different than in this shot, and color values (and even the presence or absence of leaves on the trees!) will vary in this subject as the seasons progress. In general though, you can evaluate detail in the bricks, shingles and window detail, and in the tree branches against the sky. Compression artifacts are most likely to show in the trim along the edge of the roof, in the bricks, or in the relatively "flat" areas in the windows.

This is my ultimate "resolution shot," given the infinite range of detail in a natural scene like this, and the C-750 Ultra Zoom did an excellent job. Fine detail is strong in the tree limbs over the roof, as well as in the fine foliage in front of the house. Leaf patterns are well-defined, even if just slightly soft. The in-camera sharpening system does a good job here, as details are fairly sharp throughout the frame, although I did feel that it added a certain heaviness to the finest detail. Shooting with the camera's sharpening set to its lowest level and then sharpening strongly with Photoshop's unsharp masking filter (radius of 0.4 pixels, ~180%, threshold of 2) brings out even more detail, with no trace of heaviness.

There's some softness in the corners of the image in the left side of the frame, and slightly more softness visible in the right corners as well. The camera does a surprisingly good job of holding onto detail in the bright white paint surrounding the bay window, a trouble spot for many digicams. Detail is also fairly strong in the shadow area above the front door, showing most of the brick pattern and light details, although there's quite a bit of noise present there as well. Overall though, the C-750 Ultra Zoom displays a very good dynamic range. Color is about right, as is exposure. The table below shows a standard resolution and quality series, followed by ISO, sharpness, saturation, contrast, and white balance series.

Resolution Series:

Wide Angle	"Fine" JPEG	"Normal" JPEG
3,200 x 2,400 (Enlarge size)	C75FARGF	-
2,288 x 1,712	C75FARLF	C75FARLN
2,048 x 1,536	C75FARM1F	-
1,600 x 1,200	C75FARM2F	-
1,280 x 960	C75FARM3F	-
1,024 x 768	C75FARSF	-
640 x 480	C75FARTF	-

ISO Series:
As I observed in the Indoor Portrait shot, high-ISO image noise seems to be a weak point of the C-750. Image noise here is low at the ISO 50 setting, but increases steadily, and becomes quite objectionable at ISO 400.

ISO Series
ISO 50	ISO 100	ISO 200	ISO 400

Sharpness Series:
As mentioned above, the C-750 Ultra Zoom's default sharpening is a little heavy-handed, but you it gives you a very nice range of adjustment via the menu system, letting you select exactly the amount of sharpening you want.

Sharpness Series
-5	-1	0	+1	+5

Saturation Series:
The C-750 Ultra Zoom's saturation adjustment provides a very useful range of control, in very fine steps. The steps are fine enough that you can really customize the camera to suit your personal preferences.

Saturation Series
-5	-1	0	+1	+5

Contrast Series:
The C-750 Ultra Zoom's contrast adjustment also provides a fairly useful range of control, in very fine steps. Here again, the steps are fine enough that you can really customize the camera to suit your personal preferences. However, I'd really like to see the whole range of the contrast adjustment shifted downward (toward lower contrast) somewhat.

Contrast Series
-5	-1	0	+1	+5

White Balance Series:
The C-750 also allows you to adjust the white balance, either adding more red or blue to the color balance. This is useful when the camera's white balance system gets close to a perfect match, but needs just a little help. As you can see here, the adjustment covers a pretty extreme range. (But it might be useful in correcting for very heavily colored light sources, like household incandescent or high-pressure sodium vapor lights outdoors at night.)

White Balance Series
Blue +7	Blue +4	Normal	Red +4	Red +7

Lens Zoom Range

Whooee! A *lot* of zoom! - An excellent 10x zoom range.

I routinely shoot this series of images to show the field of view for each camera, with the lens at full wide angle, at maximum telephoto (10x, in this case), and at full telephoto with the digital zoom enabled. The C-750 Ultra Zoom's lens is equivalent to a 38-380mm zoom on a 35mm camera. That corresponds to a moderate wide angle and a pretty substantial telephoto. Following are the results at each zoom setting.

Musicians Poster

Auto White Balance

Daylight White Balance

Daylight White Balance

More color cast than I'd like, but great detail and resolution.

This shot is often a tough test for digicams, as the abundance of blue in the composition frequently tricks white balance systems into producing a warm color balance. The C-750 Ultra Zoom produced the best overall color with the Manual white balance setting, despite a slight cool cast. The Auto setting fell prey to the overabundance of blue, and so produced too warm an image, while the Daylight setting had a reddish cast. Skin tones are just slightly cool and pale with the Manual setting, but look more natural than with the other settings. Despite the cool cast, the blue background has purplish tints that aren't in the original image, as do the shadow areas of the blue robe. Still, the blue robe is nearly right in hue. Resolution is very high, with excellent detail in the embroidery of the blue robe, as well as in the flower garland and beaded necklaces. (Because the original data file for this poster was only 20MB, the C-750 Ultra Zoom is capable of showing much more detail than the poster has in it.)

Standard Macro Shot

Macro with Flash

Super Macro Setting

Normal macro performance is about average, but Super Macro mode gets very close. Great resolution, detail, and color, as well.

The C-750 Ultra Zoom performed very well in the macro category, capturing minimum area of 2.77 x 2.08 inches (70 x 53 millimeters) in normal Macro mode. In Super Macro mode, the camera captured a much smaller image area at 1.43 x 1.07 inches (36 x 27 millimeters). Resolution is excellent in both shots, though the dollar bill, coins, and brooch are quite soft in the Super Macro shot, a result of the shallow depth of field when shooting this close with any camera. Corner softness is most evident in the Super Macro shot, a common problem with super close-up shots like this. The C-750 Ultra Zoom's flash throttles down for the macro area, though the long lens creates a shadow in the lower left area of the frame when you get very close. (Plan on using external lighting for the closest shots.)

"Davebox" Test Target

Auto White Balance

Daylight White Balance

Manual White Balance

Excellent overall color and saturation, but a slight underexposure.

The C-750 Ultra Zoom's Auto setting produced the most accurate white value in the large white color block and mini-resolution target. The Daylight setting produced a warm cast, and the Manual setting was a hint greenish. The image is a bit underexposed (making the white block of the MacBeth chart look a little dull), and the camera distinguished the subtle tonal variations of the Q60 target well. The large color blocks are just a little dark, but saturation is just about right. The shadow area of the charcoal briquettes has moderate detail, with low noise, and the last steps of both gray scales are just visible. Following are ISO, contrast, and saturation series. (See my comments under the Far Field section above for my analysis of these features.)


ISO Series:

ISO Series
ISO 50	ISO 100	ISO 200	ISO 400

Contrast Series:

Contrast Series
-5	-3	0	+3	+5

Saturation Series:

Saturation Series
-5	-2	0	+2	+5

Low-Light Tests

Great low-light performance at all ISO settings, although color balance is a bit warm, and noise is quite high at the higher sensitivity settings.

The C-750 Ultra Zoom's full manual exposure control and maximum exposure time of 16 seconds gives the camera excellent low-light shooting capabilities. In my testing, the camera produced clear, bright, usable images down to the 1/16 foot-candle (0.67 lux) test limit, at the 100, 200, and 400 ISO settings. (Down to about 1/2 foot-candle, or 5.5 lux, at ISO 50.) Color is good overall, though slightly warm in the dimmer shots. At ISO 100, the 1/16 foot-candle image is slightly dim, but still bright enough for use. The C-750 Ultra Zoom's Noise Reduction system did a pretty good job of keeping "hot pixel" noise in check, but there are some hot- and/or black-pixel effects in all of the longer exposures. Noise levels at ISO 50 are pretty good, but noise increases with increasing ISO, becoming high at ISO 200, and what I'd consider to be objectionable at ISO 400. (Here are sample images shot at the darkest light level, without Noise Reduction, at ISOs 50, 100, 200, and 400.) The table below shows the best exposure I was able to obtain for each of a range of illumination levels. Images in this table (like all of my sample photos) are untouched, exactly as they came from the camera.

Flash Range Test

Good intensity to about 10 feet, then slight decreases from that point on.

In my testing, the C-750 Ultra Zoom's flash illuminated the test target all the way out to 14 feet, albeit with decreased intensity at the greater distances. Flash power remained brightest to about 10 feet from the target (although the images were underexposed even at that level, I suspect due to a metering problem caused by the specular reflection from portions of the target), and then dropped in small increments of intensity from there. Below is the flash range series, with distances from eight to 14 feet from the target.

Good resolution, 1,100 lines of "strong detail."

The C-750 Ultra Zoom performed well on the "laboratory" resolution test chart. It started showing artifacts in the test patterns at resolutions as low as 800 lines per picture height, in both horizontal and vertical directions. I found "strong detail" out to at about 1,100 lines horizontally and vertically. "Extinction" of the target patterns occurred around 1,300 lines.

Optical distortion on the C-750 Ultra Zoom is a good bit lower than average at the wide-angle end, where I measured an approximate 0.4 percent barrel distortion. The telephoto end fared even better, as I measured a 0.2 percent barrel distortion. (This low geometric distortion is particularly noteworthy in a long-ratio zoom lens like the 750's.) Chromatic aberration is also quite low at wide angle, with only very light color showing around the target elements, but more evident at the telephoto end of the lens' focal length range. (This distortion is visible as a very slight colored fringe around the objects at the edges of the field of view on the resolution target.) The only other distortion noticeable was some softness in the corners of the images, most common along the left side of the frame, and strongest in the Super Macro shot.

Resolution Series, Wide Angle

Wide Angle	"Fine" JPEG	"Normal" JPEG
3,200 x 2,400 Interpolated	C75RESWGF	-
2,288 x 1,712	C75RESWLF	C75RESWLN
2,048 x 1,536	C75RESWM1F	-
1,600 x 1,200	C75RESWM2F	-
1,280 x 960	C75RESWM3F	-
1,024 x 768	C75RESWSF	-
640 x 480	C75RESWTF	-

Resolution Test, Telephoto

2,288 x 1,712 (Fine, Tele)

C75RESTLF

Sharpness Series (at Wide Angle):

Sharpness Series
-5	-2	0	+2	+5