iso 25 or 50 in Canon 550 (t2i)

[ggcanave]

Hi, It is possible to set iso 25 or 50 in photo mode on a Canon 550D (t2i) with ML 2.3? Thanks.

[ilguercio]

No.
Or yes, just overexpose a 100 iso shot by 1 or 2 stops and then restore it to the proper exposure in post.
There you go.

[bbarb]

No.
Or yes, just overexpose a 100 iso shot by 1 or 2 stops and then restore it to the proper exposure in post.
There you go.

Sorry, but is this correct?
This way you will increase noise. ISO 50 is supposed to decrease noise even further. Am I missing somthing?

[ilguercio]

Sorry, but is this correct?
This way you will increase noise. ISO 50 is supposed to decrease noise even further. Am I missing somthing?

How are you going to increase noise if an overexposed image actually gets more light than the correct exposure?
ISO isn't the only way to measure noise. If you take a shot at 100 iso underexposed by 5 stops it's going to be a lot noisier than a shot taken at 400 iso at the correct one.
Boosting more light into your shot, even if the exposure is not correct and as long as you don't clip the highlights, is the best way to get the maximum amount of light for your scene so you can get more light into the picture, improving the signal acquired by the sensor and taking the exposure back to normal in post production.
Does it make more sense now?

[bbarb]

How are you going to increase noise if an overexposed image actually gets more light than the correct exposure?
ISO isn't the only way to measure noise. If you take a shot at 100 iso underexposed by 5 stops it's going to be a lot noisier than a shot taken at 400 iso at the correct one.
Boosting more light into your shot, even if the exposure is not correct and as long as you don't clip the highlights, is the best way to get the maximum amount of light for your scene so you can get more light into the picture, improving the signal acquired by the sensor and taking the exposure back to normal in post production.
Does it make more sense now?

Agreed, but post proccess  always produces noise.
So what ever you ""earned"" at an overexposed capturing, you give it back at post proccess.
Am i mistaken??

[ilguercio]

Agreed, but post proccess  always produces noise.

No, why would it?

So what ever you ""earned"" at an overexposed capturing, you give it back at post proccess.
Am i mistaken??

Yes.

[nanomad]

Yes, you're mistaken
Noise is produced when the software has to create data from nothing. If you expose to the right properly (i.e. with no clipping on any of the 3 channels) you're actually maximizing the SNR of the image at the expense of having to manually adjust the levels in post-processing

The only advantage of very low ISO (<100) is being able to use long exposures in full daylight when you don't have a ND filter around

[bbarb]

I think you are both wrong!

Lolololololo

You are both good very good!
You have a very intresting approach whichs sounds very logical.
So you suggest to slightly overexpose images at 100 ISO and then just balance in post and in the end I will have better results, correct?

[ilguercio]

I think you are both wrong!

Lolololololo

You are both good very good!
You have a very intresting approach whichs sounds very logical.
So you suggest to slightly overexpose images at 100 ISO and then just balance in post and in the end I will have better results, correct?

Of course, but this is nothing new, really.
Two shots, both at 100 iso and same f/stop but one picture has a shutter speed of 1/100 while the other uses 1/200.
While 1/200 gives the proper exposure the longer shutter speed of 1/100 allows more light to be processed and converted into digital signal so actually you're getting more light for the same picture.
Of course, the latter picture is going to be overexposed but if you didn't blow the highlights and you bring it one stop down in exposure you're having the same picture, with a proper exposure and less noise.
More light is always better, if you don't exceed the capabilities of a sensor (e.g. dynamic range) . In this case you will still get less noise but at the expense of dynamic range, that's what happens with videos, where you're probably not so free to choose any shutter speed.
That's the main difference between movie and photo mode, really.

[bbarb]

Being honest with you, these are news to me. To be more precise I new light helps avoiding noise but I never thought of overexposing and then post balance!

So really thank you.

By using ML am getting any kind of advantage at DR or better noise controll anyway at images?

[ilguercio]

Being honest with you, these are news to me. To be more precise I new light helps avoiding noise but I never thought of overexposing and then post balance!

So really thank you.

By using ML am getting any kind of advantage at DR or better noise controll anyway at images?

No, as said, ML can't do miracles or improve your sensor performance.