Sony high ISO performance

Nordstjernen said:

Many think there is a triangle of exposure with digital:

• shutter speed
• aperture value
• ISO

But with there is just two:

• shutter speed
• aperture value

Click to expand...

All right, I was in agreement PRIOR to this one, but ... the multiplier always has to be in there. Let's say you're in manual exposure mode and have set a shutter speed of 1/100 and an aperture of f/8. If you shoot at varying ISO's for the same combo, you will get different exposures.

--
Rich

http://philosurfer.zenfolio.com/

RichV said:

Nordstjernen said:

Many think there is a triangle of exposure with digital:

• shutter speed
• aperture value
• ISO

But with there is just two:

• shutter speed
• aperture value

Click to expand...

All right, I was in agreement PRIOR to this one, but ... the multiplier always has to be in there. Let's say you're in manual exposure mode and have set a shutter speed of 1/100 and an aperture of f/8. If you shoot at varying ISO's for the same combo, you will get different exposures.

Click to expand...

The sensor exposure will be the same.

What happens after that depends on camera settings (analogue and/or digital gain) and/or processing (digital gain).

For example, the visible exposures could indeed be different due to different amounts of analogue gain in camera (say ISO 200 vs ISO 800). But the final visible exposure can be made similar through digital gain (equalizing visible exposures in a RAW converter).

RichV said:

All right, I was in agreement PRIOR to this one, but ... the multiplier always has to be in there. Let's say you're in manual exposure mode and have set a shutter speed of 1/100 and an aperture of f/8. If you shoot at varying ISO's for the same combo, you will get different exposures.

Click to expand...

No, the exposure is fixed when the image is aquired (by the shutter speed and aperture relative to the scene brightness). The ISO can be adjusted in post processing. Unfortunately, lightroom and other programs call the ISO slider for exposure slider

A fixed exposures gives the same amount of noise over a broad range of ISOs in Sony cams as I demonstrated here (where the ISO is constant in the processed images although the setting on the camera suggested otherwise):
http://forums.dpreview.com/forums/read.asp?forum=1037&message=39918014

Kind regards,

JOnas

A more meaningful attempt, at presenting, and dealing with high ISO captures has been initiated by a forum member Mandude , here:
http://forums.dpreview.com/forums/read.asp?forum=1037&message=40265778

Nordstjernen said:

Many think there is a triangle of exposure with digital:

• shutter speed
• aperture value
• ISO

But with there is just two:

• shutter speed
• aperture value

Click to expand...

ISO level can come into play when balancing ambient to flash light exposure. Sometimes aperture and shutter speed are needed for other reasons then exposure control. I'm sticking with triangle of exposure and the need for Auto-ISO in Manual Mode.

Cheers,
--

"Those who would sacrifice liberty for safety deserve neither liberty nor safety." - Ben Franklin.
You can see larger versions of my pictures at http://www.dennismullen.com .

dennismullen said:

Nordstjernen said:

Many think there is a triangle of exposure with digital:

• shutter speed
• aperture value
• ISO

But with there is just two:

• shutter speed
• aperture value

Click to expand...

ISO level can come into play when balancing ambient to flash light exposure. Sometimes aperture and shutter speed are needed for other reasons then exposure control. I'm sticking with triangle of exposure and the need for Auto-ISO in Manual Mode.

Cheers,

Click to expand...

I did NOT say that you should stop using the ISO setting! Actually, using the ISO setting is quite practical.

My point is that only aperture and shutter speed affects the amount of light that reaches the sensor. Using ISO leads to a change in the light meter, that send instructions to change one or both variables for exposure -- but ISO itself doesn't alter the amount of light that passes through the diafragm and the shutter mechanism. Nor does this affect the sensitivity of the sensor.

When you set a different ISO value, you just tell the light meter to adjust the reading. With the camera set to Auto, this reading will instruct the electronics to change one or both of the TWO variables for exposure: shutter and aperture. So also when the camera is set to manual, but then the photographer is doing the adjustment manually.

Nordstjernen said:

My point is that only aperture and shutter speed affects the amount of light that reaches the sensor...

Click to expand...

We have a different opinion of what the term exposure means.

Cheers,

--

"Those who would sacrifice liberty for safety deserve neither liberty nor safety." - Ben Franklin.
You can see larger versions of my pictures at http://www.dennismullen.com .

dennismullen said:

We have a different opinion of what the term exposure means.

Click to expand...

The technical definition of exposure is the amount of light that falls on the sensor (or film).

ISO just tells how sensitive the sensor/film is.

When discussing it is a good idea to stay with the well-established definitions.

You might refer to the photographic jargon, exposure -- taking a picture.

Hope this helps...

http://www.thephotoargus.com/101/understanding-the-exposure-triangle/

Cheers,
--

"Those who would sacrifice liberty for safety deserve neither liberty nor safety." - Ben Franklin.
You can see larger versions of my pictures at http://www.dennismullen.com .

dennismullen said:

Hope this helps...

http://www.thephotoargus.com/101/understanding-the-exposure-triangle/

Cheers,

Click to expand...

The article already misses the mark in the second paragraph:

" The ISO rating (which is an international standard) measures the image sensor’s sensitivity to light "

The sensitivity of the sensor doesn't change, ever. A sensor has no ISO rating. The resulting exposure does.

You guys try too hard!

Hail the Exposure Triangle and it's ability to properly "expose" a picture under different conditions!

Cheers,
--

"Those who would sacrifice liberty for safety deserve neither liberty nor safety." - Ben Franklin.
You can see larger versions of my pictures at http://www.dennismullen.com .

Unfortunately that guy doesn't understand that the sensor's sensitivity is fixed, at least as far as I know.
--
Tom

Look at the picture, not the pixels

http://www.flickr.com/photos/63683676@N07/
http://www.flickr.com/photos/25301400@N00/

dennismullen said:

You guys try too hard!

Click to expand...

No, we just hate to be right when getting rid of a some common misunderstandings (involving sensors).

Just semantics!

It doesn't change how the Exposure Triangle functions.
A guy shooting jpgs needs to be able to adjust his ISO sensitivity.

The sliders in Photoshop aren't real mechanical levers but they serve the same purpose.

Cheers,
--

"Those who would sacrifice liberty for safety deserve neither liberty nor safety." - Ben Franklin.
You can see larger versions of my pictures at http://www.dennismullen.com .

OK guys and girls this is getting interesting.

There are a few reasons why I started this forum.

First and most important to me is to justify whether an upgrade to a A77 from my A55 would be worth it. There is a lot of commotion over the A77 ISO performance even though the A55 never got many complaints. According to DP they are practically identical. Comparing my A55 to the 7D at http://www.imaging-resource.com/ at high ISO is like splitting hair. DXO rates the A77 at 801 for ISO and 854 for 7D and it blows the 7D out of the water as far as everything else goes like resolution, color dept, dynamic range, etc. Considering the fact the A77 has 6MP over the 7D and a translucent mirror that to me is pretty impressive.

ISO has suddenly become a very touchy subject for many and this is my second reason. I think everyone out there would love a camera that could take shots at any ISO in any condition and produce fantastic shots. There are a couple of pics that I uploaded at the top of this forum for the following reasons. Both of these shots where taken at ISO 12800 even though theoretically with other in camera settings it might be equivalent to ISO 3200 which is still pretty high. The camera was set to ISO 12800, hand held under poor lighting and there was no noise reduction applied. I guess the whole point of that was to show people that these cameras are more that capable of producing noise free images even in low light with the proper camera settings. With that being said I am not talking about fast moving subjects at night like a sports game. They make specific tools for that called "Full Frames" they also come with a price tag. Anyways I am not telling you anything you don't already know so here is the final.

I am sorry for this long post and hope this will be the longest on this forum. What I was really hoping to get out of this was some great realistic low light high ISO shots preferably from the A77. If you choose to process that's fine just let us know what was done.

Thank you all for your comments and keep those pictures coming.

issue and discussed here with varying feelings.

--
Thanks,

Digitalshooter

There are many good arguements made in this thread and the digital nature of image capture is not as simple as film, or so it seems. The amount of light falling on the sensor is the same at ALL ISOs. With shutter speed and aperture, we can control the amount of time and DOF.

There are complex alogorithms working overtime which calculate the light accumalated on the sensor at the sensor's base ISO. The algorithm then starts working based on that and applies GAIN or amplification. Everything with a digital image starts with the base ISO and works from there.

--
Nick P

dennismullen said:

Just semantics!

It doesn't change how the Exposure Triangle functions.
A guy shooting jpgs needs to be able to adjust his ISO sensitivity.

The sliders in Photoshop aren't real mechanical levers but they serve the same purpose.

Click to expand...

I understand but this has nothing to do with the original discussion and the cameras high iso capabilities based on the cameras ability to produce images in low light. Shutter speed and aperture are real physical properties at the point of capture while iso in digital is more a virtual property process after the sensor captures the image so in a way you're both right. What iso does is allow the camera to produce a proper looking exposure with varying amounts light hitting the sensor, something that used to be done in the dark room with underexposed negatives.
--
Tom

Look at the picture, not the pixels

http://www.flickr.com/photos/63683676@N07/
http://www.flickr.com/photos/25301400@N00/

this is ISO 12,800

tbcass said:

Unfortunately that guy doesn't understand that the sensor's sensitivity is fixed, at least as far as I know.
--
Tom

Look at the picture, not the pixels

http://www.flickr.com/photos/63683676@N07/
http://www.flickr.com/photos/25301400@N00/

Click to expand...

I think you need to make some new definitions. For me the way I understand it is that yes the light reaching the sensor remains the same for any ISO rating. But what is light on its own? It has to be interpreted. It is this interpretation that makes ISO to be part of the exposure triangle. Thus for a proper exposure of 1/500, f8, ISO 100 will be 1/250, f8, ISO 200. To say that ISO does not matter in exposure is understate what is really happening. Again look at the blurring and freezing effects associated with longer and shorter exposures. How can you correct that in post production if the only way to get this effect was to vary the ISO values?
--
http://www.flickr.com/photos/39182144@N03/