ISO Sensitivity

DrewMc

Hello, I am getting a little confused with the auto ISO adjustment. Am I correct in thinking the following?

1. I can turn this off for the A,S,P and M settings, and the camera won't over ride it (i.e. if I wanted to purposefully underexpose a subject I wouldn't want the camera to adjust the ISO).

2. I can also set a default setting for the other modes if I have auto turned off, and the camera will use this as default and not auto adjust (with the exception of the fully programmed mode).

I guess I want to be as creative as I can with aperature and shutter speeds, and not have to worry about the camera making a decision on ISO for me.
Can anyone suggest a reasonable default ISO setting?

As I am new here, I do apologize if this has been asked/answered before. I look forward to any replies. Thank you, Drew

Riddelske

Paragraph one and two are correct.

There are two scenes (fully auto and no flash) that have auto ISO, and this can not be changed.

If you want to underexpose I would only use manual mode anyway, because the other program modes will select either shutter speed or aperture. You would not be able to expose the image you want.

For example, if you were in manual mode you can set the ISO yourself (100 would be the lowest the D3100 goes). Then select aperture and shutter settings as you wish.

Correct me if I'm wrong, but are you looking for an ISO setting you can use for all the modes ?

If your aim is to underexpose then manual is your best bet.

ISO 100 is the best quality in respect to noise, so 100 can be used in any pro mode as well as a few set scenes.


Regards.

DrewMc

Thank you very much for your reply. Yes, I am looking for an ISO that would serve a wide range of shutter/aperature settings. I do like to underexpose subjects periodically (silhouette for example), but couldn't without the camera adjusting the ISO. I will take your suggestion of going manual for these instances. Again, thank you for your help!
Drew

Riddelske

Are you familiar with ISO and its purpose?
It can be used in a number of ways, but its main purpose is to let more light in so you can achieve higher shutter speeds.
Silhouettes can be achieved using any ISO settings, not just one. You can use spot metering and this will get the same picture.

ISO 100 is the lowest and it won't let as much light, therefore it creates less noise.
Personally I don't use any scene mode as you can obtain a much better shot using the pro modes.

Ideally, every photographer would like to use the lowest ISO possible to obtain a good quality picture but this is not always possible. To ask for an ISO that would serve a wide range of settings is impossible because different scenarios require a different choice.

If I was shooting handheld and I couldn't get the minimum shutter speed then I would have to increase ISO or find another route.

Regards.

DrewMc

Thank you again for your prompt reply. I am familiar with ISO and its purpose. I suppose I just want to be able to compensate for my exposure, either through shutter or aperature, and not have to be concerned that my camera will make an extra adjustment by changing the ISO setting. For example, when shooting in snow where my camera's meter may/will underexpose the picture due to the brightness of the scene, I would like to be able to compensate for this by either increasing aperature or decreasing shutter speed via my exposure compensation menu. To this end, I don't want to make a correction and then have the camera adjust the ISO setting to compensate for my initial correction. I hope I have explained this adequately. :) Thank you again for your help, Drew.