Image Size / Quality

The DSC-S70 offers one JPEG and one B&W GIF mode at a variety of resolutions and a TIFF mode at 2048 x 1536. The lack of alternative JPEG compression modes is a big disappointment, Sony seem to go from the sublime to the ridiculous on this subject, they took a lot of criticism for heavy JPEG compression on the Mavica range and the F505, now on the S70 they've used a light JPEG compression which generates 1,200 KB JPEG's which is great for a "FINE" mode, but there's no alternative (other than dropping resolution). For a camera supplied with just an 8MB Memory Stick it's a bit of a ridiculous situation, please Sony, include a second JPEG mode in your next camera, something around 800 KB (and minimum 16MB Memory Stick).

Standard Test Scene

To give an impression of what each combination of image size and quality produces the table below is a cross reference of image size against quality with an original image available for each, all images were shot within seconds of each other of the same subject. Please note that the TIFF images are VERY large (6.2 MB zipped) please only download these images if (a) you really need to and (b) you have the bandwidth and intend to fully download the image, otherwise you're wasting bandwidth.

Crops below are of a 200% zoomed 240 x 100 area of the image.

2048 x 1536
9,216 KB (Zipped 6,328 KB)
1,241 KB

2048 x 1360 (3:2 mode)
1,150 KB

1600 x 1200
832 KB

1280 x 960
501 KB

640 x 480
159 KB

As you can see from the top two samples that JPEG mode is almost indistinguishable from TIFF, certainly with the storage limitations of Memory Stick (and certainly the one supplied) you'd be hard pressed to find an occasion to shoot TIFF.

ISO (Sensitivity) Adjustment

This test was made difficult because you can't manually select the ISO on the DSC-S70, examining the EXIF headers of the JPEG files we can see that the DSC-S70 automatically varies the ISO (equiv. sensitivity of the CCD) when light falls below a certain level (or shutter speed would fall below 1/30s) the range of ISO's it uses seems to be between ISO 100 and 300. The three samples below were created by gradually decreasing the amount of available light on the subject and taking several shots. Unfortunately this had the side effect of confusing the cameras white balance.

ISO 100, 1/60s, F3.4 (Measured light: 9.4 EV)
ISO 183, 1/30s, F7.4 (Measured light: 6.5 EV)
ISO 282, 1/30s, F2.4 (Measured light: 5.9 EV)

Picture Effects

The DSC-S70 features several aftereffects, samples of which are shown below. I've included TEXT mode here as it is also (really) an aftereffect, reducing the image down to a 2 colour "bitmap", which can be useful for taking snapshots of print.

Date overlay
Black & White
Text mode (2 colour GIF)