expandable iso

I know what iso is but what does it mean when it says expandable up to "x" or down to "y"? Do I need to buy extra equipment to expand it?

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You don't say what camera you are shooting so that sort of limits what we can tell you. If you shot film in the past you would have bought 100 ASA film or 400ASA film. That was called the speed of the film. The higher the number the less light you needed to take a photo. The cost of that was the higher the number the noisier the photo would be. In film you would have said the photo was grainy. Modern digital cameras don't use film but instead they use a digital sensor that takes place of the film. ISO is the digital equivalent of ASA. It is done digitally instead of with film. The more expensive the camera the higher usable ISO you can use. With my D7100 I can shoot at ISO 1600 or even ISO 3200 and still get good results. With a less expensive camera like the D3100 I may only be able to shoot at ISO 800 before it gets to noisy to be good. Again, these are just examples.

Tell us why you are asking and we can probably help you more.

I am going to guess that the OP is talking about the camera specifications which are as an example for the D5300: "ISO 100 to 12800 in steps of 1/3 EV. Can also be set to approx. 0.3, 0.7, or 1 EV (ISO 25600 equivalent) above ISO 12800; auto ISO sensitivity control available"

The adds often say the ISO is 100 to 12800 (expandable to 25600). It doesn't take any extra add-ons. It is just a way of stating the EV equivalent ( I think as I am in over my head too. Ha!)

Thanks Don, I'm shooting on a D750 and the reason I'm asking is because I've noticed the camera has a LO1 below 100 and a HI1 and HI2 above 12800. I'm very new to photography but one thing I've gathered is that lower iso means cleaner shots but, is "expanded" worse than the normal range? For instance while LO1 might be less light sensitive than iso 100 the images from iso 100 are actually cleaner since they aren't "expanded"?

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colton.neil said:

Thanks Don, I'm shooting on a D750 and the reason I'm asking is because I've noticed the camera has a LO1 below 100 and a HI1 and HI2 above 12800. I'm very new to photography but one thing I've gathered is that lower iso means cleaner shots but, is "expanded" worse than the normal range? For instance while LO1 might be less light sensitive than iso 100 the images from iso 100 are actually cleaner since they aren't "expanded"?

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Click to expand...

Best to probably not go lower than 100. Search for "Native ISO" for the D750 . That is what the camera is actually designed for. Normal everyday shooting stay as low as you can and still shoot the aperture and shutter speed you need. I would never use Hi1 or Hi2 unless you absolutely have to get the photo and quality is not important. Try it some night outside with just dim street light and see how it looks. For a special effect it can be interesting.
Auto ISO can be a great help in daily shooting. YOu have the ability to set the ISO and also set the Maximum ISO. I use this when shooting Birds in Flight. I will set to Manual with a shutter speed of 1/1250 and an aperture of f8 and ISO with a maximum of 6400ISO. I also generally set to overexpose by a stop or so to get the bird exposed correctly by letting the sky be overexposed. (Again, each setting is different so this is just where I start for the shoot)

What you can take from this long winded answer is to keep ISO as low as you can while still maintaining the shutter speed and aperture where you need it to get a good photo.

On the D750 the ISO lower than 100 has no direct impact on quality but it can be used when you prefer one stop of (incoming) light more for the same scene or to use a specific aperture 100 does not allow (lowering to 50 forces you to adjust A or S) or to handle a very bright scene where your shutter might otherwise be limited by its maximum speed. I like it when shooting against the sun since I hit my shutter limit frequently then.

I use it mainly to increase my total amount of exposure to light for a shot but about only when shooting landscapes on a tripod. In doing so it indirectly impacts quality but in terms of technical quality, like the cam's DR or color sensitivity and sharpness, all below 100 is identical to ISO 100, at least for the D750. The reason I use it has nothing to do with the cam but all with the fluctuation of light.

Higher than 12800 probably has a use in very limited scenarios but the shots I took to test it were very, very noisy.