(not) BUSTED: The D200 really does(nt) cheat on its ISO speed ratings

[SP77]

NEVERMIND!
See post #25.

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BUSTED and confirmed, the D200 really does cheat by a full stop on its ISO speed rating.

I've always thought the D200 was a bit on the "slow" side as far as shutter speed vs indicated ISO. I first noticed this shooting some Kodak Portra 800 speed film indoors on my F100 with the Nikon 50mm f/1.4G lens. Swapping the lens over to my D200 I needed to crank the ISO up to 1600 to get the same shutter speed. Hmmm....

Another piece of evidence in very bright conditions. Over the winter I was shooting my D90 in full sun and bright snow, and at base ISO of 200 and max shutter speed of 1/4000s I was only able to shoot at a maximum aperture of f/4.5. The D90 was acting up so I ran into the garage to swap my 17-55 lens onto my D200 instead. ISO 100 vs ISO 200 I should be able to shoot at full aperture now at about the same 1/4000s shutter speed, right? Well I was able to shoot at the full aperture of f/2.8, but I noticed that the shutter speed was still down around 1/2000s and not 1/4k which suggested there was more than a 1 stop difference between the D90's ISO 200 and the D200's ISO 100, and possibly more like 2 stops. Hmmmm...

Well today I finally formally tested this back to back with the same 200mm f/4 AIS lens used on the two cameras, with a Gossen Digisix external meter being used as a referee. :smile:

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Conditions: Steady overcast with some light rain, and 11.7 EV. Proper exposure thus should be 1/200s @ f/4 on a D200 at ISO 100, and 1/400s @ f/4 on a D90 with a base ISO of 200.
View attachment 613452


Here's the D200 at ISO 100, 1/200s, and f/4, but that isn't a proper exposure! That's underexposed by about a full stop, and the D200's own meter said so too. :smile:
View attachment 613453


Adjusted the D200 to ISO 200 with the same 1/200s and f/4 settings as before and now that's proper exposure for the scene, but the Gossen says at ISO 200 you ought to be getting a full stop faster shutter speed. So what's going on? Let's see what the D90 does now with the same 200mm f/4 AIS manual focus lens.
View attachment 613455


Now here's the D90 also at ISO 200 and f/4, but now you get the 1/400s shutter speed for proper exposure that the Gossen says you should be getting. Ignore the minor color and white balance differences. Oh, and ignore the -1EV exposure compensation in the D90 (in the EXIF). That was from when I was doing something else before. In full manual exposure mode with Auto ISO off that setting isn't doing anything, since it has nothing it can control. Ignore it and just stick to looking at ISO, shutter speed, and aperture. ;-)
View attachment 613456


Proper exposure with the D200 set to ISO 100 and f/4 is down at 1/100s and not 1/200s. The D90 at ISO agrees with the Gossen, and the D200 is definitely cheating by a full stop. Its ISO 100 is really ISO 50!
View attachment 613458


Another D90 shot for a second example. ISO 200, 1/400s, f/4.
View attachment 613459


The D200 set to the same ISO 200 and f/4 aperture as the D90, but still a full stop slower shutter speed to get the same exposure. This is 1/200s and not 1/400s!
View attachment 613460


So the conclusion, the D200 actual ISO is a full stop slower than indicated.

Indicated ISO 100 = actual ISO 50
Indicated ISO 200 = actual ISO 100
Indicated ISO 400 = actual ISO 200
etc.

Another piece of evidence. "He who shall not be named" in his ISO 3200 test of the D3, D300, D200, and D90 also noted this difference stating that he needed a shutter speed of 1/250s on the D200 to get the same exposure that the others got at 1/400 to 1/500s, so it holds at high and low ISO and bright and dark conditions. Google that one if you want to. I've seen this mentioned by some folks in passing here at the Cafe too.

Anyhow, I actually like this. :m35: I've always loved how easy it is to shoot the D200 at very large apertures even in bright conditions without needing ND filters. Even in the brightest sun with snow reflections you can still get f/2 or even faster no problem. I've never tried it, but you could probably shoot at f/1.4 and 1/8000s in the brightest conditions there are. ND filters in these conditions might cause contrast loss and ghosting. Maybe this explains why the D200 ISO 100 is so phenomenal also? I'm guessing this probably applies to all of the other 10MP CCD cameras too, the D40x, D60, D80, and probably the D3000 as well. I knew before buying the D200 that it was never going to work well at high ISO, which is why I eventually picked up a D90 too to handle all of the work up top.

If you check the histograms on the shots above they should all be pretty close. Conditions were steady at 11.7 EV throughout the shoot, but might have varied by +/- one-third of a stop here and there. But I'm spotting a full stop difference here and it was obvious that the D200 was off. So any minor exposure variations here would be tracking with conditions and not the cameras.

Flickr set here: http://www.flickr.com/photos/spake77/sets/72157623612288718/

 

[sizzlingbadger]

It could be aperture or shutter related not just ISO. Active D lighting in the D90 will also effect it's overall exposure.

 

[BourbonCowboy]

This could also explain why the D200 is not regarded as a high ISO camera. It seems that this camera is better suited for studio work where lighting can be controlled.

 

[SP77]

It could be aperture or shutter related not just ISO. Active D lighting in the D90 will also effect it's overall exposure.

ADL can influence exposure choices, but not when I have everything set manually. All it could have done is adjusted contrast curves, but the D90 exposures turned out normal anyways. As a sanity check I'll do a quick test tomorrow with ADL turned off but I don't think it had anything to do with this. Too much other evidence.

 

[SP77]

This could also explain why the D200 is not regarded as a high ISO camera. It seems that this camera is better suited for studio work where lighting can be controlled.

nah, just need a nice selection of fast glass. This 200mm f/4 is probably the slowest lens I've ever had mounted to it. :smile:

It does explain why even 2.8 zooms can feel "slow" on the camera though. :m35: I generally don't like shooting it past 400 if I can avoid it, which is really only 200. And I'll shoot it at 800 in a pinch, which is still really only 400.

 

[sizzlingbadger]

D90 aside you have no evidence it's an ISO issue and not a shutter / aperture issue.

 

[SP77]

D90 aside you have no evidence it's an ISO issue and not a shutter / aperture issue.

I took the same manual focus lens locked at f/4 and put them on both cameras, so I don't think it's an aperture issue. Don't think it's a shutter issue either, since other people have seen the same thing. Also, the metering in the camera when left to control the exposure lines up perfect exposures. So it couldn't be a shutter that's out of sync with the camera, otherwise its exposures in auto-exposure modes would be off. So what does that leave?

 

[sizzlingbadger]

You need to check the shutter by comparing to the D90 to remove it from the equation. It most likely is the ISO but until you remove all the other variables you won't really know.

Not that any of this really matters of course :smile:

 

[silver]

it might be the d90 is faster, dpreview puts it at near spot on (along with d2x) http://www.dpreview.com/reviews/nikond200/page21.asp

doesn't dxomark also test iso settings?

 

[SP77]

it might be the d90 is faster, dpreview puts it at near spot on (along with d2x) http://www.dpreview.com/reviews/nikond200/page21.asp

doesn't dxomark also test iso settings?

That's what I was thinking, that the D90 might just be running faster than rated and the D200 wasn't "slow". But that's what the external meter was used to check, and the external meter and the D90 lined up perfectly, not the other way around. dxomark does check ISO speed, although that's one aspect of their testing that I've always thought was a little screwy due to this. They actually say that the D200 is dead-on and that the D90/D300 are both slow by a little more than a third of a stop, so .

Here's the test data from he who shall not be named, comparing to the D3, D300, and D90.

D200

The D200 is the worst. It's as noisy as the other DX cameras, has some hot pixels, and has the least retained detail. It looks terdly, but some of this is because it has less saturation to begin with since it has only Gen 1 image adjustments.

Not only this, but the D200 is cheating when set to ISO 3,200, called "High +1.0." I had to use a 1/250 second exposure to get less than I got at 1/500 on the D3 or 1/400 on the D90 and D300.

The D200, looking crappy enough set to ISO 3,200, is less than half as sensitive to light as the D3 set to 3,200. Looking at these results, I could set the D3 to about ISO 1,400, the D90 to ISO 1,800, or the D300 to ISO 2,000 to be as sensitive to light as the D200 set to ISO 3,200. If you set these other cameras to those slower values, they would look even better compared to the D200 for the same exposure.

And per my own testing, I would have had to set the D200 to roughly ISO 400 to get the same exact exposure as the D90 at only ISO 200, so it looks like the same thing is happening all the way down to lower ISOs as well and it wasn't just a fluke of his ISO 3200 test, or limited only to the D200's Hi +1.0 / 3200 setting. Unfortunately he only noticed this in this specific test where he only looked at 3200 and not any of the others where he did a full sweep.

Would be interested in hearing back from other D200 owners, and owners of the D40x, D60, D80, and D3000 which all use the same or similar 10MP CCD sensor, to see if others are seeing what I'm seeing. In fact a buddy of mine has both a D90 and a D200 as well, so I'll see if he can rig up the same sort of test.

 

[SP77]

these results seem to be the exact opposite of what you are getting

Yeah exactly.

 

[Uncle Frank]

Yeah exactly.

Check your d200 and see if you had exposure compensation set to -1ev.

 

[SP77]

Check your d200 and see if you had exposure compensation set to -1ev.

I checked - nope. :tongue:

Full manual exposure mode and manual ISO so you could set exposure compensation to whatever you want and it wouldn't affect exposure, because it had nothing to control.

 

[SP77]

well at least at iso 3200 they agree with Ken

as a side note I just checked dxomark for the D80 and D300 and as one might expect the D80 is virtually identical to the D200 and the D300 is virtually identical to the D90

But both Ken and myself are seeing two-thirds to a full stop difference, vs just a small 1/3EV trail off in the dxo results, so still not fully consistent even at ISO 3200.

 

[sizzlingbadger]

All cameras vary and change over time, maybe it just needs a service. You could test the shutter by comparing it to the D90 whilst shooting something moving at a constant speed, like a ceiling fan. See if the blur is the same length off each blade, or something like that.

 

[Growltiger]

Are you sure you had ADL off. A comment earlier said it doesn't influence exposure, which is not correct.

Here is the table showing on a D300 how the ADL setting changes exposure.

Active D-Lighting automatic exposure adjustment
Off or Low 0
Normal -1/3
High -2/3
Low with flash -1/3
Normal with flash -2/3
High with flash -1

I don't have the equivalent tables for the cameras you are testing, but it is likely to be similar.

 

[SP77]

I'll do a shutter speed comparison between the two cameras. Unfortunately I don't have a ceiling fan that I can test off of which would be ideal, but I do have something pretty close that I think will work. I might not be able to test at the same exact shutter speeds I was testing at here, but I'm guessing that if both cameras show the same amount of blur at a given shutter speed on an object with constant angular motion, then they'll probably be in sync at all other shutter speeds too.

I'm pretty sure Active D-Lighting was set to Auto on the D90, but I'm not sure what it would have been controlling since everything was set manuallly. Even if it wanted to reduce exposure by two-thirds of a stop, how would it have done so? ISO, shutter, and aperture were all set manually. Also that's suggesting that if it was active and doing something, that the difference would have been even greater? I'm not even sure that ADL works on the D90 if you have a non-CPU lens attached. I checked the D90 manual and the only thing it mentioned was a lot of features being disabled, but was vague and didn't go into specifics.

I should have time tonight to do a quick back to back test on the D90 with ADL AUTO vs OFF. I'll use the same 200mm lens set to f/4 and again use the Gossen for metering. Conditions should be similar - dreary overcast. I'll post up results after that. I probably won't be able to get to the shutter speed test until tomorrow or the next day.

Unfortunately I didn't think of things like this or even picture style modes beforehand to make everything look the same color wise between the two cameras, because I was really just out on my deck practicing taking shots with my D90 and the manual lens and external meter. :tongue: Then suddenly a light bulb lit up above my head with the idea to do this comparison, now that I could use the Gossen as a referee. Hence the sloppy settings.