5D native ISO: what is it, does it matter?

[Bart_van_der_Wolf]

I don't know why one would expect more noise?

Possibly because the route (of least resistance) is more likely to involve amplification of lesser exposed pixels than a kind of gradual anti-blooming drain of excess charge (which would potentially require some silicon real-estate to dissipate).

Bart

 

[Asher Kelman]

Bart,

It's my understanding that these pixels each act as separate camera and there is no camera shutter needed as the shtter is in the pixel, electronically.

Further each pixel can be cycled at something like 10,000 times per second. The shadow pictures would be kept open longer.

So I see no need to bloom anything!

I would imagine that ultimately the sensels getting more photons will simply be drained and recycled.

However, I had better try to find the details of the CMOS chip in question before I go beyond what I know. If anyone else knows the details of the Stanford imaging group that has produced the CMOS chip with 3 color layers. Then we could check the current specs.

Asher

 

[Dan Lovell]

Heh?

Very nice thread here, very informative, but I have two questions here:

1. In the age of Digital and Histograms, why are some still using light meters? Just take a test shot and view the histogram, then apply EC and call it a day....or am I missing something?

2. Why are some using ISO 50? On our Canon DSLR's, ISO 50 is below native ISO, has a narrower dynamic range, and I found it to even be a tad noisier, at least with my 1D Mark II, and the 5D as well.

Are some of us still "Film Conditioned"?

 

[Frank Doorhof]

1.
I use a lightmeter because it can measure ALL my lights, I'm not interested in the JPEG histogram anyway, but in the dynamic range I can get in ALL my channels with RAW. In other words, calibrate your meter to your camera and a whole new level of photography opens for you.
Accentlights and hairlights are not registered on your camera's histogram and the histogram is wildy inaccurate when you know what you are doing, it's a nice last resort.

and to be honest with a light meter I work 10x faster than with the histogram
But I use complicated light setups sometimes.

2.
I think it varies on who you ask.
I shoot ISO50 in the studio only, for a VERY simple reason I don't care about Dynamic range because I control that with my strobes (and lightmeter )
But ISO50 is VERY VERY clean and that is something that pays back in workflow.
You can achieve the same by exposing to the topright in RAW and pull back but ISO50 just is easier to incoörperate in the workflow.

But on the other hand everyone has their own opinions and workflows

 

[Nikolai Sklobovsky]

Dan,

Very nice thread here, very informative, but I have two questions here:

1. In the age of Digital and Histograms, why are some still using light meters? Just take a test shot and view the histogram, then apply EC and call it a day....or am I missing something?

Lightmeter is invaluable in the studio environment, since it allows you to set up the lights far more quickly and does not require a model to sit there for half an hour while you're running around taking and analyzing test shots (which are not that good to analyze even at 3" LCDs). With the (incident) light meter you can make absolutely sure how much light would go to her/his hair, ear, cheek, shoulder, etc. Histogram would only tell you some image average data.

I never used it when shooting "with the availalble light" though.. It's a tweaking instrument, and you can't tweak the sun

My 0.00002 of the f/stop.

HTH

 

[Bart_van_der_Wolf]

1. In the age of Digital and Histograms, why are some still using light meters? Just take a test shot and view the histogram, then apply EC and call it a day....or am I missing something?

The histogram will allow to check for, and avoid, gross overexposure. It won't allow to judge clipping of a few pixels because the histogram is too narrow, and the flashing clipping indicator may not give the right indication for all color channels. What's more, its result (as others have mentioned) is an integrated result for the entire image. A light meter allows to measure small areas within the field of view.

Lightmeters are very useful in a studio setup, because they also allow to judge the lighting contrast. Multiplying the lighting contrast with the subject contrast will set the contrast/ambiance of the total image.

2. Why are some using ISO 50? On our Canon DSLR's, ISO 50 is below native ISO, has a narrower dynamic range, and I found it to even be a tad noisier, at least with my 1D Mark II, and the 5D as well.

Actually, the native ISO is closer to 80, it has as good a dynamic range as ISO 100 or even a bit better (on my 1Ds Mk2 anyway), and it is much cleaner due to lower amplification before quantization (= lower analog gain).

Are some of us still "Film Conditioned"?

Only if it makes sense

.

Bart

 

[John Sheehy]

Actually, the native ISO is closer to 80, it has as good a dynamic range as ISO 100 or even a bit better (on my 1Ds Mk2 anyway), and it is much cleaner due to lower amplification before quantization (= lower analog gain).

I've never had RAW files to measure for myself, but my understanding from second-hand information is that ISO 50 is treated by the camera exactly a stop slower than 100, but there is only enough headroom for about ISO 75 or 80, and that the read noise was almost exactly the same as ISO 100 in ADUs; twice as high in electrons), meaning less DR at ISO 50.

Ideally, the camera would start at ISO 80, and then either have 100 and 200, 400, etc above that, or have 160, 320, etc as the native ISOs. This obsession with 50, 100, 200, 400, etc, does nothing but ruin cameras, IMO.

 

[Bart_van_der_Wolf]

Actually, the native ISO is closer to 80, it has as good a dynamic range as ISO 100 or even a bit better (on my 1Ds Mk2 anyway), and it is much cleaner due to lower amplification before quantization (= lower analog gain).

I've never had RAW files to measure for myself, but my understanding from second-hand information is that ISO 50 is treated by the camera exactly a stop slower than 100, but there is only enough headroom for about ISO 75 or 80, and that the read noise was almost exactly the same as ISO 100 in ADUs; twice as high in electrons), meaning less DR at ISO 50.

My findings, based on an analysis of analog gain, leads to several interesting conclusions:
1. Indeed, ISO 'L' will instruct the built-in exposure meter to double exposure, so 'L' could be interpreted as '50'.
2. However, analog gain is not reduced to 50% compared to analog gain at ISO 100.
3. That means that the ISO '50' file data will seem to be overexposed if the ISO 100 is optimally exposed for non-clipping highlights.
4. If the actual exposure is reduced, e.g. by using an external exposure meter set for approx. ISO 70-80, or by measuring at ISO 'L' and setting a bias of -1/3rd or -2/3rd EV, you'll get the best result:
No additional clipping compared to ISO 100, and (due to lower analog gain) a lower noise (most visible in the lowest brightnesses) which leads to a slightly better DR.

Note, I only verified this on my 1Ds Mk2 and it looks like the 1D Mk2 (N) does the same. There are reports that the 5D handles ISO 'L' in a different fashion, which I have not tested so I can't comment on that.

Bart