56

It would be wrong to think that increasing ISO results in no "physical" change in the camera at all. The problem with ISO is that people often call it sensitivity. That is really a misnomer...sensitivity is a fixed attribute of any given sensor, and it cannot be changed. Sensitivity is really more synonymous with the quantum efficiency of the photodiodes, ...


13

Is there any reason to change the ISO manually, rather than have it set automatically? The primary reason to set ISO, along with shutter time and aperture, manually would be to totally control exposure manually rather than let the camera set exposure. Not every scene needs to be rendered with an overall average brightness of medium gray. Left to its own ...


4

Think of ISO like an amplifier - it increases the gain on the incoming signal. If you have an audio amplifier & an old AM radio tuned to a distant signal, you have to turn up the amp in order to hear the station properly. Unfortunately that brings up a whole lot of other noise at the same time - so you can still barely hear the music over the crackling &...


4

For #1 and #2. Doubling exposure and stacking two exposures are going to be similar, but not exactly the same. Doubling exposure means you get twice as much signal, for a single unit of read noise. Taking two exposures means you get the same total signal as doubling exposure across both shots, but you end up with two units of read noise. Depending on how ...


4

And since the RAW files store the actual voltages read, before any changes to the brightness take place, the values in the RAW file will be the same regardless of the ISO setting. This assumption is incorrect. ISO settings in digital cameras change the amount of amplification of the analog voltage from each sensel (pixel well) before the signal is read out, ...


4

The closest thing I know to what you're thinking of is what Fujifilm are doing with DR mode in their EXR sensors, as seen in the X-10 and X-S1) - half the pixels are deliberately underexposed by a stop (or two) and combined with the "normally" exposed pixels before the image is output. For more detail, see DPReview's X-10 review - what you're interested in ...


4

Changing the ISO setting does invoke a change in the camera, it alters the on chip amplification. The voltages produced by incoming light are amplified prior to digitization. The reason for this is that the analogue signal picks up noise on its way to the ADC (analogue to digital converter). By amplifying a weak signal first, the effects of this noise are ...


3

I believe your assumption is incorrect. Though perhaps in some cameras there might be a fixed gain and the ISO is purely digital filtering (which could be done offline just as easily), I believe that on many cameras, the ISO setting actually controls the analog gain of the detector. Higher ISO is not desirable, because more gain means more noise. In any ...


3

Sensors cannot be made more or less sensitive. They simply respond to photos by freeing an electrical charge which is accumulated per photosite. That charge is an analog quantity. Technically, it discrete at the atomic level but is treated as an analog value. When ISO is set on camera what changes is the saturation point which gets mapped to the highest ...


2

Canon 7D ISO 12800 does not look like it is pure digital ISO. The raw histogram lacks those gaps at each second bin which are a sign of 2x multiplication. Also, Lr often applies ISO-dependent noise reduction; and there are other converter-dependent effects too.


2

ISO for Analog vs Digital ISO is confusing in digital photography in part because it was actually meant for film photography. In film photography, ISO 400 really is more sensitive than ISO 100 film. This isn't actually true of digital photography. The sensitivity of your camera sensor is whatever it is and does not change. The sensor works a bit like ...


1

It isn't Manual Exposure until all 3 parameters have been set to manual: aperture, shutter time, and ISO (video gain). So in situations where you absolutely must have a defined exposure, you must also get off the auto ISO. Examples: a panorama shot where you don't want brightness jumps on the stitches due to changes in exposure, a time lapse where you don't ...


1

The modern camera is loaded with automation. You can elect full automatic -- now you point and compose and take the picture using the setting dictated by the camera’s software. In many cases this image will be quite satisfactory. On the other hand, a skilled photographer might choose to reject the camera’s logic and go it alone. Now we are talking creative ...


1

Yes, there is. High ISO means lots of noise. Not all photographers want noisy images, although some minor amount of luma noise as opposed to chroma noise may be found pleasant. Also, the auto-exposure of camera might not work in all cases (examples: astrophotography, photography of moon, fireworks photography, aurora borealis photography). By setting the ...


1

yes for sure, High ISO values (like 1600, 3200, 6400) introduce more color noise in your picture which isn't a desired effect. So best to keep it as low as possible* *or as close to the native ISO of your sensor, often between ISO 100 and 200. As a photographer being used to manual exposure settings auto iso also makes it hard to over or under expose. Then ...


1

Increasing the ISO on a modern digital camera has two effects: It increases the amplification of the sensor signal, making dim parts of the picture brighter. It changes the camera metering so that a lower exposure will result. Either a faster shutter speed or a smaller aperture will be selected. Both of these combine to increase the noise. Most of the ...


1

Tetsuijn gives already a very good explanation. I try to give a similar explanation but slightly more theoretical. Assume the sensor retrieves the light an all values are between 0 (dark) to 100 (maximum light detectable by the sensor). The sensor which has a width X (with columns 0 to x) and height Y (with rows 0 to y) has pixels X * Y (e.g. a sensor of ...


1

That is due to the signal-to-noise ratio being higher when exposing properly than when you underexpose and raise exposure on a RAW processor like Lightroom. Setting the right ISO in-camera produces higher quality shots than raising the exposure in post-processing. If perfect exposure can't be achieved, you either overexpose or underexpose. I personally ...


1

I've been looking at the issue that you see more noise in the High ISO show than the Iso 100 shot even though everyone is telling you that is should be opposite. People are telling you why it should be opposite and Jrista told you why the effect is not as apparent with your camera as with e.g. Canon cameras (near equal). But your notice that it seemed to be ...


1

In order to minimize noise, you want as much light as possible on the sensor, subject to (1) not clipping highlights in which you want to preserve detail, (2) setting aperture for your desired depth of field and (3) setting shutter speed for your desired motion blur (subject and camera) or lack of motion blur. Will increasing ISO help if you do the ...


1

Although not incorrect per se, the statement in that answer is confusing. The answer is not comparing noise at different ISO settings, it's comparing the difference between analog and digital amplification. Setting a higher ISO uses analog amplification, so that performs better than under exposing the image and compensating in post processing, as that uses ...


1

There is a noticeable difference if you are shooting in a wide light range. An example would be a bright sunny day with high contrast. I have a sony a7r. The native iso is 100 but I can shoot the iso at 50. I started shooting most photos at 50 to have as little grain in my images as possible and have that crystal clear image. On most photos I didn't ...


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