Nikon "Lo-1" ISO

[Chris Nuzzaco]

Does anyone here know anything about the Nikon D700's "Lo-1" ISO setting? It's said (by Nikon) to be the equivalent of ISO 100. My curious question though: Is it really a lower sensitivity, or is this some kind of faked lowering of sensitivity via in camera processing?

To me it sounds a bit fishy, so thats why I'm poking around for answers. I'm looking at buying the D700 in January.

Thanks!

[Daniel Browning]

It's the exact same thing as ISO 200 with +1 EC.

[Chris Nuzzaco]

It's the exact same thing as ISO 200 with +1 EC.

Could you elaborate on this some more? I assume "EC" means exposure compensation?

[Daniel Browning]

I assume "EC" means exposure compensation?

Yes.

If you use manual exposure, Lo-1 *is* ISO 200. They are the exact same in every way. If the RAW is 1/3 stop overexposed at f/4 and ISO 200, then it will be 1+1/3 stop overexposed at f/2.8 and ISO Lo-1, and 1+1/3 stop overexposed at f/2.8 and ISO 200.

If you use auto exposure (AE), "Lo-1" will go behind your back to set the camera to ISO 200 and exposure compensation (EC) to +1 and proceed to overexpose every shot by one stop.

Nikon could offer an ISO 50 and ISO 25 if they wanted, 2 and 3 stops overexposed, respectively, but then more photographers would probably complain about how useless they are. Lo-1 is useless for the same reason.

It's a marketing gimmick. Photographers want an ISO 100 so they can use wider relative apertures and slow shutter speeds in bright daylight without ND filtration. But the sensor is literally incapable of slower speeds. Marketing would rather make the photographers blow their highlights than remove that feature from the list of features.

Keep in mind that the actual number of the ISO (e.g. 200, in the case of Nikon) is totally arbitrary and chosen by the manufacturer to suit their marketing desires.

One convention for assigning ISO is "the ISO is set so that 18% gray is 3.5 stops below full well capacity in the RAW green channel in sunlight." By this convention, the 5D2 "ISO 100" is actually ISO 73, 400D and 5d1 are 87, 20D is 135.

On top of that, what the camera AE system *meters* for is yet another Marketing gimmick. The 5D1 "true" base ISO is 87, but it meters for ISO 108, which gives you slower shutter speeds than a camera that was truly ISO 108 and metered for ISO 108.

If those Marketing guys had any guts, they'd stop doing dirty tricks to fool people into thinking the camera is one or maybe two stops better than it is and just go for the whole kit and kaboodle: a camera with "ISO 42 million!!!" that just meters for ISO 200 and has a true ISO of just 100. Obviously, then people would see how fake all the ISO numbers are and start wondering what the true sensitivity and read noise of the camera is.