ISO 50 - Reduced DR on original DP's

ISO 100 is DEFINITELY the one to stick with, from what I experienced with my SD14. For some reason the colors of the sunrise were "off" when I shot it at ISO 50. They would get over-saturated, which I guess would be that dynamic range issue. You can see that it does not always happen though. Take a look at the 6 shots of the sunrise down near the bottom here: http://ffphotos.zenfolio.com/sigmasd14

That's an ISO series, stating with ISO 50 and going all the way up to ISO 1600, with comments to the right of some of the photos (when you click on the thumbnails). You can download the full-size, original jpegs from that gallery, if you like. Just use the menu button that appears in the top left, when you mouse over the large image, after clicking a thumbnail.

Sorry it's not a full ISO 50 analysis. I was just doing some experiments. I have more somewhere, but I think the hard drive is up in Virginia. My stuff is strewn all over the place!

Scottelly wrote:

ISO 100 is DEFINITELY the one to stick with, from what I experienced with my SD14. For some reason the colors of the sunrise were "off" when I shot it at ISO 50. They would get over-saturated, which I guess would be that dynamic range issue. You can see that it does not always happen though. Take a look at the 6 shots of the sunrise down near the bottom here: http://ffphotos.zenfolio.com/sigmasd14

That's an ISO series, stating with ISO 50 and going all the way up to ISO 1600, with comments to the right of some of the photos (when you click on the thumbnails). You can download the full-size, original jpegs from that gallery, if you like. Just use the menu button that appears in the top left, when you mouse over the large image, after clicking a thumbnail.

Sorry it's not a full ISO 50 analysis. I was just doing some experiments. I have more somewhere, but I think the hard drive is up in Virginia. My stuff is strewn all over the place!

I assume you are talking about the image SDIM6721, which is ISO 50. It is exposed at 2 seconds. The next is ISO 100 and is exposed at 1 s.

As have been said before, the SD14 has no AFE. So, changing ISO do not do a thing, (except changing exposure if you choose to do so) and storing ISO 50 in meta data.

What happens here is that the camera exposes more so the brighter parts gets outwashed colors.

Now, this image is overall rather dark. Did really SD14 choose this exposure? Let it to choose exposure all by it own it feels like it should be brighter. So, I wonder if you have done any compensation - either manually or with the exposure compensation setting?

If so, then the test has no value.

Roland Karlsson wrote:

Scottelly wrote:

ISO 100 is DEFINITELY the one to stick with, from what I experienced with my SD14. For some reason the colors of the sunrise were "off" when I shot it at ISO 50. They would get over-saturated, which I guess would be that dynamic range issue. You can see that it does not always happen though. Take a look at the 6 shots of the sunrise down near the bottom here: http://ffphotos.zenfolio.com/sigmasd14

That's an ISO series, stating with ISO 50 and going all the way up to ISO 1600, with comments to the right of some of the photos (when you click on the thumbnails). You can download the full-size, original jpegs from that gallery, if you like. Just use the menu button that appears in the top left, when you mouse over the large image, after clicking a thumbnail.

Sorry it's not a full ISO 50 analysis. I was just doing some experiments. I have more somewhere, but I think the hard drive is up in Virginia. My stuff is strewn all over the place!

I assume you are talking about the image SDIM6721, which is ISO 50. It is exposed at 2 seconds. The next is ISO 100 and is exposed at 1 s.

As have been said before, the SD14 has no AFE. So, changing ISO do not do a thing, (except changing exposure if you choose to do so) and storing ISO 50 in meta data.

What happens here is that the camera exposes more so the brighter parts gets outwashed colors.

Now, this image is overall rather dark. Did really SD14 choose this exposure? Let it to choose exposure all by it own it feels like it should be brighter. So, I wonder if you have done any compensation - either manually or with the exposure compensation setting?

If so, then the test has no value.

If I had allowed the camera to choose the exposure for that dark scene, it would have been horribly over-exposed, and you wouldn't even know it was a photo of the sunrise.

PrebenR wrote:

Kendall Helmstetter Gelner wrote:

SRT201 wrote:

Interesting. So there's no gain on the imager and it's all just a matter of underexposure and multiplication during the development stage.

In that case then the ISO 50 with -1 compensation should be identical to ISO 100's normal exposure. Correct? Fairly easy to test.

"In theory there is no difference between theory and practice. In practice there is."

- Yogi Berra

Are the Quattro's ISO-less as well?

All of the Sigma cameras are.

That said, when using SPP to actually process the raw files they do not behave as if they were ISO-less.

You should test and see what happens (especially in the shadows), but I agree with the statement that you lose about a stop of highlight recovery.

I thought the Quattros had AFE. If it is only in SPP, then it would be interesting to hack the RAW images of the Quattros to change ISO. Roland, any pointers?

The Quattros DO have AFEs.

If they didn't, this wouldn't happen:

http://sigmadp2quattro.blogspot.fr/2014/07/gestion-de-bruit-electronique-campare.html

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PrebenR wrote:

SRT201 wrote:

Interesting. So there's no gain on the imager and it's all just a matter of underexposure and multiplication during the development stage.

There is gain in terms of better IQ. I'm puzzled why people obsess about DR. For the most pleasing photos, people have reduced the DR in post anyway.

Here is a photo I took years ago. In this I reduced the DR in post quite a bit to obtain something more pleasing: https://www.flickr.com/photos/prebenr/6284631384/in/album-72157627678060149/

How did you reduce the dynamic range of that photo? I see black in it, and I see white in it. In fact, the bright areas in those building windows would be totally over-exposed, unless there was enough dynamic range in the shot or it was under-exposed a lot, for the rest of the scene.

To me, a scene with a lot of dynamic range in it, such as the one in that photo, requires a camera with a great dynamic range to really show well. Maybe I'm mistaken.

But to say that using a camera with a big dynamic range causes your photos to look like snapshots doesn't make sense at all. Maybe it's the world of high dynamic range photography creeping into every-day snapshots that makes you think this, but there are HDR photos that look VERY professional and nothing like snapshots, and there are non-HDR photos that look like snapshots, and vice-versa. The dynamic range of the camera used has little or nothing to do with whether a photo looks like a snapshot.

Not saying it is a goo picture, but if one wants to have an indefinite DR then things starts to look like snapshots.

In that case then the ISO 50 with -1 compensation should be identical to ISO 100's normal exposure. Correct? Fairly easy to test.

No.

Are the Quattro's ISO-less as well?

No.

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Scottelly wrote:

If I had allowed the camera to choose the exposure for that dark scene, it would have been horribly over-exposed, and you wouldn't even know it was a photo of the sunrise.

Exactly!

So, all you have shown is that your own very personal choice for exposure made the 100 ISO image look better than the ISO 50. If you had chosen 1 stop less exposure, none of the pictures would have had blown light parts.

So, you have NOT shown that ISO 50 is a problem.

Scottelly wrote:

The Quattros DO have AFEs.

If they didn't, this wouldn't happen:

http://sigmadp2quattro.blogspot.fr/2014/07/gestion-de-bruit-electronique-campare.html

Yes, they have AFE. It is a rather unusual AFE though. It is a compromise between no AFE and the AFE all (almost all?) non Sigma cameras have.

For "normal" cameras AFE (plus digital amplification) will normalise the RAW data so that the RAW converter do not need to know anything about the AFE setting. But, Quattro does not amplify the signal proportional to chosen ISO, so you still need to know how to scale the data for correct exposure.

Brilliant (IMHO) but confusing.

PrebenR wrote:

Use ISO 50 if you know what you are doing.