ISO 50 - Reduced DR on original DP's

Scottelly said:

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!

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Roland Karlsson said:

Scottelly said:

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!

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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.

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PrebenR said:

Kendall Helmstetter Gelner said:

SRT201 said:

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.

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

- Yogi Berra

PrebenR said:

Are the Quattro's ISO-less as well?

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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.

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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?

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PrebenR said:

--
Lightwriting with Sigma dp2Q for stills and Blackmagic Pocket Cinema Camera for video

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PrebenR said:

SRT201 said:

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

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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://flic.kr/p/azmnXw

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PrebenR said:

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

PrebenR said:

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

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No.

PrebenR said:

Are the Quattro's ISO-less as well?

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No.

--
Lightwriting with Sigma dp2Q for stills and Blackmagic Pocket Cinema Camera for video

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Scottelly said:

PrebenR said:

SRT201 said:

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

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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://flic.kr/p/azmnXw

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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.

Scottelly said:

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

Scottelly said:

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

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No.

Scottelly said:

Are the Quattro's ISO-less as well?

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No.

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Roland Karlsson said:

jande9 said:

Roland Karlsson said:

DMillier said:

ISO 50 is just overexposed ISO 100. It is useful for lower contrast subjects as you get a bit more exposure in the shadows. But shooting ISO 100 with +1EV exposure comp will yield the same file.

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Yes, except that they are displayed and converted (by default) differently by SPP. The JPEG, the LCD and also standard SPP conversion, will render the ISO 50 image darker than the +1 compensated image. But, the RAW data will be the same.

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Roland Karlsson said:

SRT201 said:

I really don't know why Sigma had to artificially make that sounds so hi-tech. The "Analog Front End" a term very common in signal processing is a gain stage that amplifies the signal from the imager (in this case).

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That is common practice. Your product do not have something that almost all other have. The day you add it you try to make it sound as something fantastic.

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Scottelly said:

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.

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Scottelly said:

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 said:

Use ISO 50 if you know what you are doing.

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