ASA - film speed

[Richard Mason]

My digital camera allows me to set a range of sensitivity, akin to the old ASA for film speed, in fact it’s listed as 100, 200, 400 and (maybe) 800ASA, along with an auto-setting.

So most of my pics, I’m using my strobe - what circumstances would I use which setting?

I know from the days of film that the more sensitive ASAs resulted in poorer quality because of increased grain size – what will happen in digital? Will I simply get bigger clumps of similarly coloured/shaded pixcels?

[John63]

Hi Richard,

can't make a recommendation regarding iso sensitivity and strboe as I've just conerted over to digital myself but yes the faster the iso/asa setting the grainier (or noisier in digital parlance) the result will be.

I'm sutre that some of the much more experienced digital buffs will be able to give better advice.

Cheers

[triplefin]

same principle Richard, higher setting more noise, I try and stay clear of 400 and use 100 and 200

[ChristianG]

Originally Posted by Richard Mason

I know from the days of film that the more sensitive ASAs resulted in poorer quality because of increased grain size – what will happen in digital? Will I simply get bigger clumps of similarly coloured/shaded pixcels?

If you substitute the word "grain" for "noise" you've pretty well got it digitally sorted.

Here's a quite reasonable interpretation of what digital noise is about:

Noise: Digital Imaging: Glossary: Learn: Digital Photography Review

[Cussy]

Richard,
What I do is up the ISO for natural light and keep a low ISO if the strobe is attached (no higher than 200). The only time I up ISO/ASA with a strobe is if the light is failing to reach the distance, upping it effectively makes the light travel a little further. As the strobe is giving artificial light you don't need to introduce noise/grain, let the flash do the work; but remember flash light is going to travel only a metre or two.
Rob

[Mike Ward]

...and turn the auto ISO setting off - otherwise anytime the camera detects low light levels it'll up the sensor sensitivity!

[Cussy]

Originally Posted by Mike Ward

...and turn the auto ISO setting off - otherwise anytime the camera detects low light levels it'll up the sensor sensitivity!

Very good advice that. I spent two days in the Red Sea shooting with Auto ISO on; my mistake as I didn't think the auto ISO worked in Manual mode, so a lot of the macro shots were at 400 and you can see the noise. There are a couple that would have been much better at 100.
Rob

[ChristianG]

Originally Posted by Cussy

There are a couple that would have been much better at 100.

Rob,

I venture to say that the lower the ISO/ASA that you can make it, the better will be the picture quality.

Back in the "good old" days I was a happy chappy when Fuji came out with Velvia 50 which we quickly learned to shoot at 40 (but get developed at 50) and which knocked the previous preferences, Kodachrome 25 and 64, into the proverbial cocked hat pretty well instantly. It was the advent of Fuji dominating the colour scene, which they understand superbly well but which they have recently spoilt with their latest P&S cameras going the way of the marketing people and megapixel rubbish.

Incidentally Fuji have recently re-introduced Velvia 50 film, no less, which was discontinued years ago in its original format for production reasons. Looks like there are still a fair few film photographers around.

[Scuby]

Be careful in taking the advice above without understanding the difference between your camera and the ones on which people are giving advice. Some digital cameras are very noisy above ISO 200 or 400, where as others (such as the Fuji F-series) will take very clear noise-free pictures at 800.

With my Fuji F30 for example I tend to take a lot of my underwater photos with natural light, and so need a high ISO to get the sensitivity up, but not too high that I get noise in the picture. With the Fuji I tend to use ISO 800, because it gives very very good sensitivity (can get excellent photos in very low light) without any signs of noise in the picture.

So depending on your camera, you may or may not be able to do the same.

David

[Cussy]

Originally Posted by Scuby

Be careful in taking the advice above without understanding the difference between your camera and the ones on which people are giving advice. Some digital cameras are very noisy above ISO 200 or 400, where as others (such as the Fuji F-series) will take very clear noise-free pictures at 800

David,
I disagree. I processed a load of photos for my mate that he took in Cyprus using a 31fd. It is far from noise-free at 800 and you can see noise at 400. If you only view on screen then its fine, but if you want a decent high quality print then 800 is too high.
Rob