The Sony "high ISO" thing.

[bfitzgerald]

Not to start a war off, or be super critical. However I can increasingly see what the "problem" is, regarding high ISO performance (at least on the A200, I see similar things on the A300/350, not sure about the A900 not seen enough shots), no experience of the A700, so I will let users give feedback on those models.

The A200 "exposure wise" (and I use the term as a reference to in camera metering and tonal curve), is a cautious beast in many situations. This is probably a good thing for bright sunny days, and contrasty shots, it mostly does a good job. I have seen some underexposure when there are many light tones present in an image, and on overcast days it can go under a bit too.

A few examples here:
http://www.photoclubalpha.com/forum/vie ... ing#p14324" onclick="window.open(this.href);return false;

The problem is that for high ISO work, the metering can remain too cautious, and it is not giving, in many cases enough "exposure" to the shot. This can lead to more noise present than there need be, and a lack of details in the shadow areas. In low kelvin light, blue channel noise is a serious issue too, though you get better results with different raw converters.

Note this thread on Dyxum, clearly showing the issue.
http://www.dyxum.com/dforum/how-many-ar ... 45496.html" onclick="window.open(this.href);return false;

Note the blue channel noise problem on the globe crop. I believe that the cautious exposure on some sony models, is good for most in low ISO shots, where the retention of details in highlights is most likely a desired thing. In low light situations, this hurts the performance of the camera. I would suggest that Sony consider an adjustment of metering and or tonal curves to address this weak spot. And I am sure this is a least one reason why, sony consistently are rated worse than most rivals in the high ISO performance area.

I can compare directly the A200 to the Km5d, which is doing the reverse..giving more exposure, geared more towards shadow details. On bright days you will probably need to dial the 5d back to hold onto highlights, but in low light, it is giving a very good performance v the A200, noise is much less an issue. I am also pretty sure, that at ISO 1600/3200 the 5d is rated near to the actual ISO levels indicated (if not even a tad over), the A200 is not givng as much exposure as the KM, so I believe the ISO settings are less than those indicated

BTW I am not complaining, just making my own observations!

[David Kilpatrick]

I've compared Nikon and Sony models in low light with high ISO several times - most of the time, the Sony camera will give one full step less exposure than the Nikon. Not only that, but the Nikon uses a tone curve which crushes the deep shadows to black and compressed the rest of the range closer to linear - removing loads of apparent noise in the process (black level clipping). The combination of clipping the black and increasing exposure transforms a high ISO shot.

In ACR, you can try the effect - take a normal (dark) ISO 3200 shot on an A700 or A900, and set the black level slider to 0 and the tone curve to Medium Contrast. The shadows, where noise is most visible, will look very bad. Now increase the exposure by +1 but clip the black level to 10 (the default is 5) and set the tone curve to Linear.

What I found was that if I used the default Nikon D3X tone curve with the Sony A900 in Iridient RawDeveloper (one of the few programs which allows such a switch of 'hidden' processing parameters), then increased the Sony exposure to match the Nikon, the A900 high ISO really was much the same the Nikon high ISO - far better than any default result. So, it is not an inevitable fault of the camera, more a badly chosen combination of in-camera and external processing parameters which makes Sony high ISO worse than it needs to be.

David

[springm]

This matches my experiences when using high ISOs: 1600 gives a good IQ with +0.7 exposure compensation, of course carefully watching the highlights then. Without this compensation, the shadows easily become too noisy and postprocessing can not help out too much any more. Of course loosing 2/3 of an f-stop makes the whole ISO 1600 thingie quite questionable.

But once more your observations underline my feeling, that camera tests based on jpg results tell only part of the story.

[Vidgamer]

I figured it was just DRO+ that caused it to underexpose a tad (to preserve highlights) but maybe you're right that there's more to it than that.

The last time I dealt with blue channel noise, it was partially due to being low-light tungsten, so it was a bit of a WB problem as much as anything else. I imagine that there is much less blue light available to do anything with! What I found strange was that I tried a couple of different raw converters and some handled it better than others. Chroma NR was really necessary! A bit of that, and it actually looked fine. Without it, it was a blue-speckled mess. Go figure.

[douglasf13]

I've found that setting ZONE to -1 in the A900 helps exposure a lot when shooting RAW, as it actually physically changes the exposure. It's almost as if the A900 has Canon's Highlight Tone Priority on all that time, and setting ZONE -1 changes the way the camera meters and leaves less highlight room.

Also, for more detailed shadows, shoot ISO 320, which was discovered by Iliah Borg. Apparently, the extra gain helps drives the ADCs better, and produces better shadow detail. I use ISO 320 almost always for outdoor shots, now.

[SLUFDRIVER]

May just be me, but back in the day when we all were using our Minolta or other 35mm kit, what film speed was most frequently inside? I cannot remember going over 400 other than BW with any frequency. If I had a $ for every roll of 100 or slower I shot I'm certain I could throw us all one tremendous bash! Yes, I pushed some lots in an 'emergency' but honestly, I shot tons of slow 'chromes.

[bfitzgerald]

Well for me one of the great uses of digital is the high ISO element. Add the SSS/AS to the mix and we have potent tools for low light work. You are right, few did shoot over ISO 400 film, but for me at least..this is one reason I have some interest in digital. I couldn't really care much about the low ISO stuff, I prefer film for most subjects

[Dusty]

I'm with you, Slufdriver. Most of my settings are under 400. I've done shots from the balcony at weddings on 1600 film, and used 3200 film in the Pharaoh's Tombs when in Egypt, but shoot very little at higher ISOs. Yes, it is nice to have it at times, and the fact that you can change w/o changing rolls of film is *sweet*.

If I can ever get back to having some fast primes like I did with the MD mount, I'd need the high ISO even less.

Dusty

[Vidgamer]

This matches my experiences when using high ISOs: 1600 gives a good IQ with +0.7 exposure compensation, of course carefully watching the highlights then. Without this compensation, the shadows easily become too noisy and postprocessing can not help out too much any more. Of course loosing 2/3 of an f-stop makes the whole ISO 1600 thingie quite questionable.
...

I think ISO 1600 looks underexposed for some reason on my A100. Even 800 starts to look a bit darker. I suspect that this was intentional, but curious as to why. Meanwhile, I know that just because Sony labels it ISO 1600 it isn't exactly standard 1600. (I think I read where it's more like ISO 2000, so +.3 EV could be easily justified, I think. )


One of my big dislikes about film is having to choose the ISO well in advance, without knowing for sure where I might be... I do so much indoors or dimmer light that I have to lean towards higher-speed, even if I use it a lot outdoors too. I don't think I used ISO 800 too often (but sometimes). ISO 200 sometimes. ISO 100, not so much. I'm happier keeping "auto" iso on!

[springm]

One of my big dislikes about film is having to choose the ISO well in advance, without knowing for sure where I might be...
...
I'm happier keeping "auto" iso on!

Yes, one of the big advantages is that additional freedom in ISO. For me shooting is interesting when there isn't full daylight anymore, beeing it at home or abroad, and sometimes these parts of the days can also be the only occasion for photography due to duty constraints. So I was very happy that Auto-ISO is indeed very usable with the A700 and noise can be kept at bay with RAW and Noise Ninja without loosing to much IQ. A whole lot of my China shots from last year would have been impossible without reasonable high ISO settings.

Markus

[bfitzgerald]

The next thing to say is, simply this.

If there are issues with exposure overall, and this impacts performance. Why are these issues not being addressed?

[douglasf13]

There are a few things to know about the A900. It meters middle grey to green channel saturation at +3.2 EV, so spot metering the detailed highlights at +3.0 EV, works well. Or you can spot meter middle gray at +.5 EV. Secondly, those that use matrix metering can try setting -1 ZONE, as it actually changes the way the camera meters, and -1 will boost your exposure an extra click. There is also a tone curve changed involved, so you may not wanna do this if you're shooting jpeg. Secondly, ISO 320 is the ideal ISO of this camera. The ADCs of the A900 are numerous, but rather poor, and they have problems with linearity in the shadows and clip at ISO 200. Using ISO 320 gives a little bit of preamp boost, which improves the ADC performance and cleans up the blobby shadows. Below ISO 200 is simply an overexposure of ISO 200, so there's no real reason to use it, unless you're shooting jpeg.

[harvey]

Concerning underexposure (which I much prefer by the way than overexposure)...

Would it make sense and be practical to have a meter/drive mode where the camera takes one image and then internally calculates the histogram then immediately takes another shot by biasing shutter/aperture to just get the highlights. In A/S mode A or S should stay fixed. Second shot is written to card.

Really small highlights might give you a problem.

[Vidgamer]

If forced to choose between the two, I suppose I'd prefer underexposure, and Sony does give you that.

OK, we're talking about high ISO, but after reading your message, I wonder about a more general question of protecting highlights. I think, in general, even when you blow the highlights, if you used JPEG+RAW, you can probably process the RAW and recover some (not all) of the information and get some of the highlights back. So, when processing JPEGs, the camera already has some information on "just getting the highlights" and still decides to sacrifice them in some cases. I haven't done testing on this specifically to try to see what it's doing, but if I'm concerned about the dynamic range, I shoot RAW. DRO+ does help though.

As for a mode to take two photos, what about an EVIL or P&S type camera that can give you a live histogram? Is it too much of an estimate?

If you want to get really fancy, we should be able to select from different modes -- protect all highlights, protect most highlights, etc.

Concerning underexposure (which I much prefer by the way than overexposure)...

Would it make sense and be practical to have a meter/drive mode where the camera takes one image and then internally calculates the histogram then immediately takes another shot by biasing shutter/aperture to just get the highlights. In A/S mode A or S should stay fixed. Second shot is written to card.

Really small highlights might give you a problem.

[Dr. Harout]

I second Don (Sonolta), and that's what I've learned from him. I tried myself, and can say that for example at 1600 ISO you should overexpose AT LEAST by 0.7 (well, at least for the A700). And don't forget to shut down the high ISO NR within the menu.