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Help with ISO speed


ian_w 14 22 United Kingdom
7 Feb 2008 11:44AM
Whilst I've had my SLR, I've mostly been point and shoot, using the zoom, as well as some other modes (P, S, A, sometimes M) so that I can control shutter speed and aperture.

However, I've not done much with ISO, and always been using it on 200. Speaking with a friend last night, mentioned that when using indoors and natural light, to use ISO 400.

So, now I'm just generally trying to understand when I would change ISO speed. This is what I'm basically thinking in layman terms, so please correct me:

ISO 100: Outside, bright sunny day
ISO 200: Outside, slight compromise if not bright and sunny
ISO 400: Indoor, natural lighting
IS0 800: Unsure on this one
ISO 1000: Fast photography, such as sport.

As I mentioned, laymans terms, I'm trying to understand when and why I would change it, so any nice easy explanations would help me immensely!

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FatHandedChap 13 1.3k England
7 Feb 2008 12:02PM
In general terms, use the lowest ISO possible to give you your desired shutter speed and aperture.

If your shutter speed gets too slow then you run the risk of camera shake. As a rule you need the reciprical of your focal length (ie - 50mm lens, shutter speed 1/50th sec or faster).

In lower light conditions you may need to raise the ISO to give you a fast enought shutter speed, the same with sports - if you need a faster shutter speed then raise your ISO accordingly to be able to freeze the action.

If you are using a tripod for landscape work then this doesn't matter as you won't have the effects of camera shake to worry about.

Hope this helps.

Tony
John_Frid 13 514 57 United Kingdom
7 Feb 2008 12:02PM
Basic advice is to shoot at the lowest ISO whenever you can. Increasing the ISO effectively increases the sensitivity of the sensor and allows the use of faster shutter speeds or smaller apertures than would be available otherwise.

So, if the lighting isn't good enough for the required exposure, then increasing the ISO allows you to get the shot.

However, increasing the ISO leads to more digital noise. To be fair, most cameras will be pretty good at up to ISO 400, but above that the noise can start to be a problem.

Of course, if it is a choice of getting the shot with a high ISO or not getting it at all, then go for it and see the quality of the result.

Hope that helps.
ripleysalien 13 1.2k 11 United Kingdom
7 Feb 2008 12:04PM
No, use the lowes ISO you can until the situation dictates you need to change.

ie, set ISO to 50, and shoot say outside then if you move indoors and the light is still bright and you can do what you need to, leave it at 50, if its darker then open the apature or change the ISO.

Steve

Crossed post , like wot the above said.
csurry 17 9.2k 92
7 Feb 2008 12:05PM
Well you can work the way mentioned above, but I guess it depends how you think.

I think in terms of aperture and shutter speed. I know what aperture I want for DOF, I know what shutter speed I need to "freeze" the subject or to be more artistic, and thus I adjust the ISO to suit.

Indoors, because I use a tripod for still life I use the lowest possible ISO as shutter speed is not relevant - generally, but I suspect you mean taking pictures of people maybe at a party or something.

Sometimes when we actually get sunshine you can end up with 1/2000th sec or faster at ISO 100, so there are no real hard and fast rules.

Sure someone like Vince or John will be along with a better explanation.
ripleysalien 13 1.2k 11 United Kingdom
7 Feb 2008 12:07PM
Sunshine, I remember that from my childhood days, a warm bright light i think....................

Steve
ian_w 14 22 United Kingdom
7 Feb 2008 4:25PM
OK, I think I understand that. Effectively, increase the ISO when lighting is not so good. Or, if things are moving so fast (motorsports) that you want to freeze-frame them, then you increase here also.

So, one more question. If I'm shooting indoors and using the flash, would I still go for a higher ISO (400), or would you still use 200 for this?
csurry 17 9.2k 92
7 Feb 2008 4:50PM

Quote:So, one more question. If I'm shooting indoors and using the flash, would I still go for a higher ISO (400), or would you still use 200 for this?


Depends on distance to subject.

The higher ISO will effectively distribute the flash over a greater distance. If you have one with an LCD readout you will see that as you change the ISO upwards the distance reading may for instance got from 1 - 2.6m to 2 to 5m. Those are of course just examples.

Else there should be a similar table in the manual.
irweazel 13 167 England
7 Feb 2008 5:13PM
the default setting is 200 for flash guns, but with digital use your best judgment, stick it on 400 and if it looks alright then thats the right setting
ian_w 14 22 United Kingdom
7 Feb 2008 5:17PM
I don't know where I'm supposed to see this - but nothing is obvious on my camera with regards to this. I'll have to check the manual.
csurry 17 9.2k 92
7 Feb 2008 5:18PM
Sorry meant on the flashgun, or are you talking about the in-built one? In which case definitely check the manual
ian_w 14 22 United Kingdom
7 Feb 2008 5:21PM
Yep, it's the built-in flash. Am downloading the english manual now from Nikon, since the manual I have is in Polish (live in Poland) - and I have trouble understanding it Smile
ian_w 14 22 United Kingdom
8 Feb 2008 8:06AM
I took a look at the manual but it doesn't seem to show anything in there about distance etc. I suppose I can guess on that.
csurry 17 9.2k 92
8 Feb 2008 8:38AM
All I can find Ian is the GN meaning a coverage of 12m at ISO 100, which isn't a great help as the camera doesn''t have ISO 100 Smile

However, what I did find is that the SB-400 seems to be highly recommended with the camera if the internal flash is not enough. This is quite a compact gun, so may be worth considering.

Sorry couldn't find anything more helpful except a suggestion to set the camera to auto ISO so that it will adjust automatically to ensure enough light is recorded from flash and ambient light for a successful exposure.
ian_w 14 22 United Kingdom
8 Feb 2008 11:59AM
Thanks csurry, glad for the help you've provided me. I was thinking about auto ISO when I was looking through the manual, but didn't want it to unnecessarily cause noise if it chose the wrong one or forced a higher ISO than I would normally want I suppose.

I'll have a play with the ISO's and do a bit of testing based on ambient lighting and see how each fares out, and then decide if I change manually, or let auto decide for me.


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