What Quality setting should I use?
I've often been asked which Quality setting
should be used, as it has a great influence on the number of pictures you can
get onto a memory card. The Nikon 990 offers three different compression
or "Quality" levels - Basic, Normal and Fine - with typical image file
sizes of 400KB, 700KB and 1MB. Note that we are not talking
"Resolution" here. Resolution is the number of pixels which make
up the picture - normally 2048 x 1536 - although lower resolutions such as 1024
x 768 and 640 x 480 are also available and will result in smaller file sizes.
We've been using Nikon 900/990s for few years now, and we have always used the Basic setting. Yes, it would be nice to use a higher setting, but with the memory as expensive it was, with the need to take all storage with us, and without anything like the Digital Wallet, it was really the only choice.
However, like you, we first established that we could see minimal difference between the Normal and Basic quality settings. There are a couple of mitigating factors here.
Where might this be different for me?
There are some circumstances where using Basic may be inappropriate for you:
(I've only once seen the grey slate roof problem, and that when I had the combination of VGA and Basic. The JPEG compression has no colour information to offset the compressed grey levels).
Of course, if you have the time, you can check the picture on playback, and re-take if necessary. The great thing is with the small file size, when you are back home, you can keep all your "masters" as well as any cropped or reprocessed images. BTW, if cropping is all you do, use the lossless JPEG cropper, because there is no quality loss.
You might want to use Normal or even Fine if you know you are going to do significant processing or enlargement, or if you can see that the subject would benefit from the higher quality.