Help!..Confused Re: Iso & Shutter Speed, outside vrs inside.

[mandab99]

Hi Guys

I have been experimenting with ISO and shutter speed. I took a series of photos outside which had direct sunlight in them as well as shade. I wanted to keep my aperture value the same so I took them in AV mode and changed only the ISO, increasing from 100 up to 6400. The results were what I thought would happen with the shutter speed increasing as my ISO increased... That made sense to me, the sensor is more sensitive so the shutter doesn't have to stay open for as long.
So then I took a series of photos inside, which was poorly lit and done the exact same thing of increasing my ISO. The results were not what I expected...the shutter speed got slower as the ISO got higher?
Can someone please explain why this is? Obviously it is not as straight forward as I thought :eek:

[ameerat42]

Wh-a-a-a-a-t? That sounds odd 2 me 2. Can you post two shots to illustrate the indoor phenomenon? Keep the EXIF intact.

Ta, Am.

[mandab99]

Sure I can Am. The only thing is how do I keep the EXIF intact? Sorry never done it before:o

[ameerat42]

OK. Open the image in something that will re-size it for posting here. (DO NOT just copy the image and paste it into another file.)
When you have re-sized the image, save it with ANOTHER file name. Eg. Image01.jpg - reisize it - save as something like Dark01.jpg.

If you have Photoshop you can see the EXIF (a bit scattered about) using the File - File Info... command
And again, if you have Photoshop, use the File - Save As... command and that will let you give a new name to the file you have been working on. It will leave the original intact.

Just DO NOT do an ordinary Save command while you're working. Always use Save As... instead.
Am.

[mandab99]

Thanks Am for your help :) But I have just realized that I have been reading my EXIF wrong!!! Feel like a idiot!!! ....So sorry for wasting your time :( I must say I am glad that that was all it was. Thanks again :)

[ameerat42]

OK. I'm guessing it was the way the shutter speeds were listed, with a few leading 000s.
Am.

[4wdexposure]

If you double the ISO you have to halve the shutter speed - assuming the aperture remains the same. The relationship between shutter, ISO and aperture will always be constant.

[mandab99]

Am, it wasnt that!, it was my stupid brain looking at the info and for some reason computing back to me that the SS was getting faster not slower...a bit like me!LOL
Thanks 4wdexposure for the tip!!! Can you maybe give me a example?

[kiwi]

#1 Example Correct Exposure (for example based on the given light) = 1/200s, iso100, Apperture F/8
#2 Example Correct Exposue (for the same amount of light in #1) = 1/400s, iso200, Apperture F/8

So, I doubled the iso which allowed me to double the shutter speed to get the same exposure

[mandab99]

Gotcha! Thanks Kiwi ;)

[ricktas]

Think of the exposure triangle like this:

You are standing in a room looking out a window, the window has heavy drapes on each side that you can move. These drapes are your aperture, so by closing them in and only letting a bit of light in, you are copying aperture f22, and by opening them up to allow the window to be fully seen you are now at f2.8.

Now your window also has a blind, that you can pull down to cover the entire window, this is your shutter.

You put on a pair of dark sunglasses (the ISO), in this instance with the glasses on is equal to ISO 100.

So you are standing there, sunglasses (ISO 100) on, the drapes (aperture) are closed up with a small gap in them. How do you get more light into the room? You can open the drapes ( change aperture) or you can take the glasses off (increase your ISO - sensitivity to light), which will give YOU more light. Now your blind that can be brought down is your shutter speed, the longer the blind is up for, the more light hits you.

So to get a good exposure, without to much light from the sun that is blazing in the window you need to set a balance between the drapes (aperture), blind (shutter speed) and your sunglasses (ISO). This is the exposure triangle.

[mandab99]

Rick this room sounds a awesome place to be in when hungover!!!......seriously though a great perspective on it thanks!