Night photography - strange PSAM metering

I like to take photos at night and was excited about how much less noise the D3300's sensor has compared to my D40

So I set the ISO to 12800 and the mode to matrix and P and got this!


Setting it to M and giving it 1.6 seconds instead of 1/6 of a second and got this:


Using P, A or S I have to dial in about 4 stops of "over-exposure" to get a decent picture?!

Is it because the meter is only good to about -1 EV, that it won't go below that?

cheers!

Dominic

Welcome to Nikonites!

I'm pretty sure there's a low shutter speed threshold where the semi-auto modes won't drop the shutter speed to something that can't be captures hand held. I don't have the D3300 manual in front of me, but I believe that the same applies to my D5300 and D7100.


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I have never tried the Program mode in VERY dark setting like that. I always use Manual since I normally know what I am after. Movement, DOF stopping star movement etc.

The D3300 spec chart in user manual (also about all Nikon DSLR models) specs the light meter range at 0-20 EV, specifying at ISO 100 with a f.1.4 lens. So I suppose a f/3.5 lens would be about 2.67 EV less range.

P mode only has a somewhat narrow range where it works. The meter can work over a wider range, but not P mode. One reason is that P mode also uses a chart of the permissible values it can use in that range, and it won't go below EV 4 (at ISO 100).

And if flash is used, P mode also limits the low end even more, and then even more at high ISO than at low ISO. So, if we buy a f/1.4 lens for flash, P mode will never use f/1.4 with flash, so possibly not the best mode for flash in dim light. But P mode can be of advantage for TTL BL fill flash in bright sun (P mode knows to accommodate Maximum flash sync speed, and will try to keep us out of HSS flash mode... where A or M mode doesn't, if HSS is allowed ... it needs our attention).

I don't think the D3300 manual includes the chart, but here is a P mode chart from a D800 manual. For example, if ISO 100, if P mode chooses f/4, it will also say 1/60 second (from this chart). We should never confuse automation with intelligence. Just meaning, we may of course have reasons to choose other values, but P mode does not know them. And P mode won't go below EV 4 (at ISO 100). The D3300 P mode will be a similar idea (I don't know if the same exact values or not, but should be fairly close).




P mode chart shows near EV 11 minimum with a f/3.5 lens.

Thanks for the detailed info! Nice to know I'm just expecting too much

The other thing that threw me for a loop was the behaviour on Manual when Auto-ISO was enabled. I kept dialing in longer shutter times and yet the image stayed black, since the camera was dropping the ISO to match!!!

vladhed said:

So I set the ISO to 12800 and the mode to matrix and P and got this!



Setting it to M and giving it 1.6 seconds instead of 1/6 of a second and got this:



Using P, A or S I have to dial in about 4 stops of "over-exposure" to get a decent picture?!

Is it because the meter is only good to about -1 EV, that it won't go below that?

Click to expand...

I don't really want to go here, because it makes no sense to me.

Is the 'about 4 stops" always required, or just in this dark scene?

Looking deeper, your Exif in the second Manual picture says ExposureDifference +3.5 EV. That is the difference in the actual exposure used, and what the meter thought it ought to be (if the meter could affect Manual mode). That seems very unusual, I'd say the picture was a couple of stops UNDER exposed (-2EV), but +3.5 EV says it is far the other way, overexposed.

Continuing that, the first black picture in P mode says ExposureDifference 0 EV, claiming it is properly exposed. Which it should normally be 0 EV when the automation modes handle it, but I think this one is not properly exposed. And that is also your complaint.

Makes no sense, something seems wrong. Why, I dunno. Says 18-135mm lens, which should be very compatible. Says Exposure Compensation is 0 EV. Says Bracketing is off.

It might be explained where it says Light Value is -1.8, which is pretty dark and out of range. But it seems to have measured it anyway? I'm not sure the numbers are supposed to make sense there. I'm sorry if this is just a confusion.

I guess I wondered if normal snapshots in normal light were coming out OK?

Thanks for the analysis Wayne,

To answer your question, yes any picture taken of a scene at -1 EV or more is properly exposed. Anything -1EV or less will be exposed as if it were -1 EV. So if the scene is really -2EV, I need to dial in +1 compensation to get it to add a stop of exposure.

So in summary, the process for night photography is the same as the D40:
1) turn off Auto-ISO
2) guess at the exposure
3) take picture
4) look at the picture - if not right, go back to 2)

vladhed said:

Thanks for the analysis Wayne,

To answer your question, yes any picture taken of a scene at -1 EV or more is properly exposed. Anything -1EV or less will be exposed as if it were -1 EV. So if the scene is really -2EV, I need to dial in +1 compensation to get it to add a stop of exposure.

So in summary, the process for night photography is the same as the D40:
1) turn off Auto-ISO
2) guess at the exposure
3) take picture
4) look at the picture - if not right, go back to 2)

Click to expand...

That's always been true of night pictures in the dark, the meter is not of much use in the dark. Both the D40 and D3300 say metering range is 0..20 EV (ISO 100, f/1.4). One big difference though is that the D3300 will show much less noise at long exposures and high ISO than will the D40.