Help me understand ISO - it's confusing the hell out of me?

[Big Mike]

I read somewhere, that most (if not all) film sold as ISO 1600, was actually just ISO 800 film that was intended to be 'pushed' when developed. So clever photographers would just use 800 (or even 400) film and just under expose it, then develop it in such a was as to get the exposure they wanted. This resulted in more grain, or at least more pronounced grain, so the same principle still held true...that a lower ISO gives you cleaner images and higher meant more grain.

 

[SCraig]

... ISO = ASA by the way. ...

Question, just for my own information. ASA = American Standards Association. Did they really use ASA in Europe? (I was never there so that really is a question). I thought they used DIN in Europe. Or maybe I'm thinking of something else.

 

[Helen B]

... ISO = ASA by the way. ...

Question, just for my own information. ASA = American Standards Association. Did they really use ASA in Europe? (I was never there so that really is a question). I thought they used DIN in Europe. Or maybe I'm thinking of something else.

ASA was widely used in the UK, although the change to ISO was made a fairly long time ago (1974) and there was a BSI speed that was very similar to DIN in concept. DIN tended to be used more on the continent. The original ISO speeds were given in both old ASA and DIN, and even now you can use either, so ISO = ASA or ISO = DIN. It wasn't that ISO took over from the ASA, but that ANSI (the successor to the ASA) became the leaders of the ISO photography technical committee.

I read somewhere, that most (if not all) film sold as ISO 1600, was actually just ISO 800 film that was intended to be 'pushed' when developed.

ISO 1600 colour neg was usually a true ISO 1600, and marked as such. Film manufacturers did not usually sell a lower speed film as an ISO 1600 film, it would be sold as an EI 1600 film, not an ISO 1600 film. There was Ektachrome P1600 reversal film which was an ISO 400 film intended to be pushed two stops (hence the 'P' in the title) but Kodak never claimed that it was ISO 1600. It's a similar situation for Ilford's Delta 3200 and Kodak's T-Max P3200 - they are ISO 800 to 1000 and ISO 1000 to 1250 films respectively, sold as EI 3200 films.

 

[SCraig]

ASA was widely used in the UK, although the change to ISO was made a fairly long time ago (1974) and there was a BSI speed that was very similar to DIN in concept. DIN tended to be used more on the continent. The original ISO speeds were given in both old ASA and DIN, and even now you can use either, so ISO = ASA or ISO = DIN. It wasn't that ISO took over from the ASA, but that ANSI (the successor to the ASA) became the leaders of the ISO photography technical committee.

Interesting, thanks for the clarification. I had never even thought about it until I saw that post. Having never been to Europe I wasn't sure whether they actually used ASA or not.

 

[Rephargotohp]

The original ISO speeds were given in both old ASA and DIN, and even now you can use either, so ISO = ASA or ISO = DIN. It wasn't that ISO took over from the ASA, but that ANSI (the successor to the ASA) became the leaders of the ISO photography technical committee.

QUOTE]

Maybe I am just misinterpreting what you are saying but ISO= DIN? Would that really be true since one is arithmetic and one is Logarithmic? Best I recall ISO/ASA 64 was 19 DIN - 1 DIN 1/3 stop Or were you just refering that DIN was film speed?

The other thing DIN recalls, is how big Germany was at one time in Camera design and industrial design

 

[Helen B]

The original ISO speeds were given in both old ASA and DIN, and even now you can use either, so ISO = ASA or ISO = DIN. It wasn't that ISO took over from the ASA, but that ANSI (the successor to the ASA) became the leaders of the ISO photography technical committee.

Maybe I am just misinterpreting what you are saying but ISO= DIN? Would that really be true since one is arithmetic and one is Logarithmic? Best I recall ISO/ASA 64 was 19 DIN - 1 DIN 1/3 stop Or were you just refering that DIN was film speed?

The other thing DIN recalls, is how big Germany was at one time in Camera design and industrial design

As I said, you can use either DIN or ASA speeds as the ISO speed. You can use both at once if you wish. 100 ASA = ISO 100 = 21° DIN = ISO 21° = ISO 100/21°.

The various ISO standards for film speeds (still B&W neg; still colour neg; still colour reversal) all include both arithmetic and logarithmic methods.

Regards,
Helen

 

[Rephargotohp]

I guess my only point was for people that may have never seen DIN numbers That ASA/ISO 100 Did not = DIN 100 and I didn't want people to misinterpret that.

Thanks

 

[radiorickm]

Well, my explination of DIGITAL ISO relates to listening to your home stereo system.

When you first turn on the stereo, and have NO music playing, the stereo is pretty quiet. But, if you turn the volume all the way up (increase amplification), you will hear a HISS, and that is NOISE!

So now imagine listening to a cassette recording made in a big room. You have to turn the volume way up to be able to hear what happens in the room. But, you gain a whole lot of hiss in the process. The key here, is the ratio of the "signal" to the noise. You, in this case have a very underexposed situation, with a very low signal to noise ratio. The low signal relates to a dark scene, and the high noise relates to all that hiss created by the amp being turned all the way up.

But now think about playing a CD. You can turn the volume control way back down, because have a properly exposed signal reaching the amplifier, and it doesnt need all that extra gain, creating hiss. You also have a much better signal to noise ratio; loud signal (lots of light) and hardly any noise, very low amplification.

Of course, you can have too much of a good thing also, and overload the amp by putting too much into it, aka overexposing.

This is probably over simplified, but it has helped several people I have worked with understand the process a little better. Hope it helps.

 

[classixuk]

Well, my explination of DIGITAL ISO relates to listening to your home stereo system.

When you first turn on the stereo, and have NO music playing, the stereo is pretty quiet. But, if you turn the volume all the way up (increase amplification), you will hear a HISS, and that is NOISE!

So now imagine listening to a cassette recording made in a big room. You have to turn the volume way up to be able to hear what happens in the room. But, you gain a whole lot of hiss in the process. The key here, is the ratio of the "signal" to the noise. You, in this case have a very underexposed situation, with a very low signal to noise ratio. The low signal relates to a dark scene, and the high noise relates to all that hiss created by the amp being turned all the way up.

But now think about playing a CD. You can turn the volume control way back down, because have a properly exposed signal reaching the amplifier, and it doesnt need all that extra gain, creating hiss. You also have a much better signal to noise ratio; loud signal (lots of light) and hardly any noise, very low amplification.

Of course, you can have too much of a good thing also, and overload the amp by putting too much into it, aka overexposing.

This is probably over simplified, but it has helped several people I have worked with understand the process a little better. Hope it helps.

You might need to update that analogy soon RadioRickm. Cassettes will be as mystifying as ISO to the younger generation.

 

[Helen B]

It confuses me somewhat. As I read it I asked myself: What has the room size got to do with it? Why is the cassette recording at the wrong level? Do you mean the mic was a long way from the sound and the mic amp wasn't turned up? What is tape hiss analogous to? (Why was a cassette chosen?) Why didn't they use Dolby? (that last one's not serious). Isn't the analogy much simpler: the microphone has internal, self-generated noise (that is independent of the sound arriving at the mic); the quieter the sound being recorded the more the mic amp has to be turned up to reach the standard recording level, so the more the mic's own noise is amplified.

Best,
Helen

 

[sm4him]

The best way to use it, is almost a last resort.

Yes and no. I think that the 'last resort' advice is taken too seriously by many who don't fully understand the issues involved.

For example, if someone is afraid to use ISO 800 because they are worried about noise...that they end up taking photos at 1/50 (on say, a 50mm lens)....they will likely get some amount of blur (lack of sharpness). If however, they use ISO 1600 and a resulting shutter speed of 1/200, they are likely to get much sharper photos, but of course, with more noise. But the thing to remember is that you can't truly get rid of blur, but it's much easier to deal with noise. And even so, noise can usually be stomached by the viewer much easier than a lack of sharpness.

The the moral of the story is....don't be afraid to turn up the ISO if it means getting a sharper photo (due to faster shutter speed).

+1
MLeek said basically the same thing, and a light just went on inside my head..this is EXACTLY what I tend to do, because I have a DSLR but I'm still living in my film days.
I tend to treat ISO 800 as the absolute maximum I can go up to because in my head, anything above that would be Bad. But then I end up with an underexposed shot, and I think oh well, I'll just fix it in post. I "fix" it in post, and hate it, because it's too noisy.
And not once in the 5 months I've had this camera have I thought, "well, you dummy, if you're gonna end up with a noisy picture anyway...UP THE ISO!"

 

[thereyougo!]

With my Pentax 645N (film medium format) I often use 50 ASA black and white and have some Velvia 50 waiting for developing. Ilford PanF 50 is superb film that resolves very well with very fine grin indeed. First time I used Velvia 50 I trusted the 645n's meter and most of the shots were underexposed. I need more practise with the film...

 

[Fred Berg]

Great thread - love the time of day guide!

Perhaps it would help to take things a step at a time and set the iso and change the other factors around this. Iso 200 is a very good number to work with in most daylight conditions, I find. Something you might want to think about is picking up a hand-held light meter (they can be had for little money on ebay). You may well ask why do this when your camera has so many metering modes and options; well, yes, of course it does, but if you check things through for yourself, you will come to develop a deeper understanding of the relationship between iso, aperture and shutter and will also get a feel for light and shooting conditions. Modern cameras are all singing and dancing but they can't think like us.....yet.

 

[classixuk]

Hi Everyone,

I am the OP, and I want to thank you all for your advice. I've read each and every reply and considered everything you have told me (although I still don't understand the Hi-Fi analogy/metaphor).

But I've been thinking about this thread and all of the advice given for most of the day.

So far, I'm still feeling my wariness about using anything over ISO 800 because ingrained in my mind is ISO 800 = Grain/Noise (from my days of film).

I am willing to try out these new super duper high ISO's but I am still rather skeptical.

Today (whilst racking my brain about avoiding high ISO when your aperture is the on the largest setting and you are maxxed out on exposure already) I had a fleeting thought.

Rather than raise my ISO, couldn't I just take along a tripod and then raise my exposure time to get a better shot?

Now I appreciate, for this I would have to be sure that my subject isn't going to be moving (bad time to be shooting in Japan or New Zealand I guess) but in my limited understanding of the theory so far, surely a tripod (for static subjects) is a far better solution? Increase the exposure time in those instances rather than the ISO to get the very best shot you can?

I know I am new, and I know that this is all new to me, but I generally learn in life by applying the theory to the practical before I start a job.

Please can you tell me if my above assumption is correct or just stupid?

Thanks.

 

[LightSpeed]

It's very simple.
Sensor Sensitivity to light increases with higher ISO allowing for faster shutter speeds, smaller apertures. But it comes with a price in the balancing act, that is photography.
That price is signal to noise ratio. IE noise.

It doesn't always work as depicted in your last post.
What if, the wind is blowing while you're shooting a landscape, and there's moss hanging from a tree in the scene?
At a 5 second or a 1 second exposure at ISO 80. Then what happens?