ISO

[Solarflare]

Noise can always be added in postproduction, though.

At least if you know your way around tools like Photoshop (I dont).

 

[jake337]

Yes Nikon cameras have an Auto ISO setting.

You can set it on/off, you can set a maximum ISO, and you can set a minimal shutter speed.

I really love this automatic, except it would be really more comfortable if there was a direct dial instead of having to do menu surfing.

You love auto ISO? ISO is the one thing that I can never deal with having auto. I can shoot in shutter priority, aperture priority, but auto ISO drives me crazy. Your pictures get these wild jumps in feel that is really annoying and very difficult to fix in post.

So you rather have all your pictures equally noisy, instead of having each with the least amount of noise possible ?

To each their own, I guess. I'm used to having an automatic like this from my previous camera, a G11, and I love having an even more powerful automatic now on my D5100.

The main reason I could think of why anyone wouldnt want to have this automatic is that Canon DSLRs, as I heard, didnt had it in the past.

And as of right now I never "tell stories" with my pictures, so I dont really need them at the same quality of some sort.

I guess thats like the swirvel monitor. I keep hearing people complain about how superflous they are. I love them. I guess thats because I'm new to photography and thus I can see the advantage of them, while others did photography for decades and dont see why they need such stuff now.

Having it in auto simply denies you control over what your camera is doing.

 

[BuS_RiDeR]

These might be helpful...

Digital Photography 1 on 1: Episode 16: Exposure: Adorama Photography TV - YouTubeDigital Photography 1 on 1: Episode 26: Metering Part 2: Exposure Compensation: AdoramaTV - YouTube

 

[christop]

I know the noise aspect of increasing ISO in camera vs in post has been discussed to death already, but I want to throw in my two cents anyway.

As I hope we all agree, increasing ISO in camera amplifies the analog signal more than lower ISO values before it is digitized. Doing so in post is a simple multiplication of the digital signal, which amplifies the digital quantization error: Quantization error - Wikipedia, the free encyclopedia. The quantization error might be significant relative to the magnitude of analog noise, depending on the bit depth and quality of the analog-to-digital converter (ADC).

To illustrate what I mean, imagine a camera with a high-quality sensor and analog amplifier and a 4-bit ADC. The digital signal will be a very crude approximation of the relatively noise-free analog signal. Indeed, the digital signal would consist of one of 16 different values (2^4 = 16) per data point. Obviously, boosting the ISO in post will show the digital noise but not the analog noise. This is a clear win for boosting ISO in camera.

On the other hand, imagine a camera with a very noisy sensor/amplifier and a 24-bit ADC. The data will be quantized down to one of 16777216 distinct values. Sounds great, doesn't it? Sure, but the source analog signal is much, much noisier than the quantization error, so boosting ISO in post (you can boost it by 8 stops and still get 16-bit data out of it) is probably no worse than boosting ISO in camera in this case.

So... my take on it is there is no clear benefit to boosting ISO in post vs in camera (though this does assume that analog noise is amplified linearly with ISO). Amplifying the digital signal amplifies both the digital noise (quantization error) and the analog noise.

 

[Theninjaseal]

ISO is not persay an algorithm or a processing technique, but rather a sort of system. There is a sensor. Each pixel has a counter that counts the number of photons that hit the sensor, for the duration of the shutter speed. Photons by themselves do not have much energy, but they transfer their inertia to the sensor when they collide. That energy is transmitted to an amplifier. Much like an electric guitar, photons by themselves produce a charge on the sensor (the sound of strumming). In the way that a guitar's acoustic sound isn't loud enough to fill a concert hall, a proton's inertia isn't enough to provide a bright and clear picture. So -before- the information is sent to the camera's processor, it is directed into the amp unit. This unit works like a guitar amp. It takes the raaaaw data -energy directly from the protons- and it boosts them up to a desired level. But the more you turn up the "volume," the more distortion you create. If you've ever turned speakers up way too loud and they sound like crap, then you've experienced a similar phenomenon. The ISO setting is a standard for the voltage supplied to this amp unit. And again, too much power results in a brighter (louder) picture, but more noise (distortion). If you recorded a guitar with the amp up too loud, and the guitar was distorted, then you couldn't change the power of the amp in post. Just like you can't change the voltage applied to the photon amp in post.

So you see, ISO is as much of the exposure as aperture and shutter, and it has its own gives and takes in regards to a darker/brighter picture. Please excuse any physics errors, I am not a mathematician nor a scientist - Just a photographer.

 

[Solarflare]

Having it in auto simply denies you control over what your camera is doing.

I dont have it in AUTO, I have it in aperture priority.

And AUTO ISO is doing exactly what I would be doing would I be doing it by hand.

 

[christop]

But the more you turn up the "volume," the more distortion you create. If you've ever turned speakers up way too loud and they sound like crap, then you've experienced a similar phenomenon.

This distortion from turning up the volume too high is from oversaturation, not regular amplified noise. Saturation in a guitar amp is the same as blowing out the highlights in a camera sensor. The background hiss you hear when you're not strumming the guitar (or strumming lightly) is more analogous to the noise from a camera's sensor. Strumming lightly with the amp turned up high is like taking a picture in low light with a high ISO--more noise relative to the signal than you'd get while strumming harder (more light) with a lower volume (lower ISO).