I have a K-x and just got a Sigma 18-250mm lens for a trip to Haiti. I plan to be taking many photos outdoors of people, scenery, etc. What is the optimal ISO setting to get full rich pictures?

[MarkJerling]

As the general rule, the lower the ISO the better. Having said that, my K-5 makes good pictures up to ISO 1600 and even decent ones at ISO 3200. If I can help it, I like to stay below ISO 800.

[mattb123]

Lowest is typically best but you need the lowest that gives you an adequate shutter speed for that aperture. If it's very bright, ISO 100 is usually your best bet.
I like to use auto ISO set to a range of 100-3200 (K-3, K-1) which seems to like picking 200 in bright conditions which on my cameras looks very similar to 100. That way if conditions change and get darker ISO will increase.
I try to keep ISO low unless I need extra-fast shutter speeds and/or have low available light shooting with a moving subject.
Static landscapes on a tripod always get ISO 100. My 645D starts to get noisy at ISO 400 so I almost exclusively shoot that camera at 100 on a tripod.

[jab2980]

Looks like the low end native ISO on your camera is 200 and the noise increases considerably after 1600... so I'd work within that range. Remember that noisy photos are better than blurry photos, and if it comes down to having higher ISO vs needing to raise exposure in post, take higher ISO every time.

[mikeSF]

for outdoor daylight handheld shooting, a typical strategy is to keep ISO as low as possible to permit a fast enough shutter speed to prevent motion blur. This is where some of the auto modes such as P, Tv, and TAv come in, to give you one or more adjustable parameters to which the camera will compute a correct exposure.
I almost never leave ISO100, but I use a tripod for everything, always.
good luck!!

[photolady95]

Looks like the low end native ISO on your camera is 200

Sorry but that is incorrect. My K-x will go as low as ISO100.

On mine I find any over ISO800 introduces too much noise.

[amoringello]

I have a K-x and just got a Sigma 18-250mm lens for a trip to Haiti. I plan to be taking many photos outdoors of people, scenery, etc. What is the optimal ISO setting to get full rich pictures?

Outdoors during sun? Rain? Night?
People moving or static? Scenery sharp, or perhaps smooth waterfalls under heavy tree cover?

Regardless, the answer is always: the lowest possible to get the shot you want in the time (and/or shutter speed) allowable/required.

[pathdoc]

Stay as low as you can for the best quality, but remember that that lens is a slowpoke at 250mm. Not only do you lose the better part of two stops relative to 18mm, but this happens right when you want your shutter speed to be highest to stop you from getting camera shake. If you anticipate gloriously sunny days and photographing things in bright sunlight you will be fine; otherwise there may be a price to be paid in quality for usable, non-shaky shots (even with SR).

[pschlute]

Sorry but that is incorrect. My K-x will go as low as ISO100.

On mine I find any over ISO800 introduces too much noise.

He specifically used the term "native ISO". The KX can go lower to 100, but that could result in image deterioration as its native ISO low setting is 200. In practice I doubt you could tell the difference.

[Na Horuk]

ISO, shutter speed, aperture. You need to compromise.
a) Lower ISO is better
b) Which aperture is optimal depends on the lens, but usually you get most resolution stopped down one or two stops. For DoF you want higher aperture, but below the diffraction limit. f8 is a good balanced aperture for great DoF and great resolution
c) Lower shutter speed means blur is more likely. Sometimes you want a little blur, but usually you want things to be sharp. For telephoto lenses (and also for high magnification macro purposes) you need need fast shutter speed, or handshake blur will become apparent.

Which ISO? Lowest possible ISO that still lets you use the aperture and shutter that you need. With modern DSLRs, you can go up to ISO 3200 or even 6400 without the digital noise ruining your photo. Lower ISO means less noise and better quality of the recording. This means ISO is not a big problem to worry about in even halfway decent light conditions. It was a bigger problem with older generations of digital cameras, or back in the film days when a whole roll of film had just one ISO and you couldn't change it for each photo

Edit: With K-x I would try to stay under ISO 800. But personal preference plays a role - some people want zero noise, some people don't mind it much. You can take some test photos and compare them at full resolution to see the noise

[C_Jones]

Lowest ISO possible is the key to avoiding the presence of noise (fragmentation) in your images. Try to stay near 100 or 200 ISO if possible. The range for a shoot in which you want to retain detail would most likely be 100-800 ISO. Staying stationary for non-action shots like static (basically still) landscape using a tripod will let you take advantage of a low shutter speed (long exposure) that enables you to also use a low ISO like 100 for your shots. When doing action you can use the required shutter speed and F Stop (aperture) and try to make due by adjusting the ISO within the 100-800 range if you can. The TAV mode may be handy for you when you are on the go without a tripod. Using that mode you can adjust the shutter and F Stop (aperture) and the camera will automatically yield the proper ISO for those settings most of the time unless you have for instance a lot of glare on the subject that it cannot evaluate easily. In situations where you have time, Manual mode will be the most effective/valuable, and the metering display in that mode will tell you how your settings are dealing with the available light. Manual mode when using studio lights/flashes is valuable because you have complete control of the type image you want per the lighting you are using.

Those are examples of basic guidelines. Using methods during shooting will show you what works best and the trial/error that may go along with it will teach you. Reading my manual and using different methods during shooting has shown me how to actually apply different methods in different situations that are effective. You can also review images to see what settings were used and when for the results you get and see what is working best for you.

Good luck and happy shooting.

[clackers]

I'm very happy in good light outside to go with ISO 200 when handheld, JHawk93, to increase the shutter speed for a sharper shot.

Doing landscapes on a tripod is the reverse - sacrifice shutter speed to get ISO 100.

[goatsNdonkey]

I have a K-x and just got a Sigma 18-250mm lens for a trip to Haiti. I plan to be taking many photos outdoors of people, scenery, etc. What is the optimal ISO setting to get full rich pictures?

As said, in bright lighting conditions, keeping ISO as low as possible is a great idea.

BUT -- if you want to get those rich pictures, at night, indoors, in shady settings, you will want to become adept at using higher ISOs when needed. It is that or leave a lot of pictures behind. It might be worth learning about the kind of noise your camera gets at high ISOs in low-light conditions. Some noise isn't as bad as other noise, as with grain in film. It could be that one of your most memorable pictures, pushing the camera to its extremes will be full of noise, but the image will be such that no one looking at it is going to complain about that. The picture will be taking their attention elsewhere.

[MrB1]

As others have commented, I keep the ISO as low as is practical for a suitable aperture and shutter speed. I don't know about the K-x but on my (more recent) Pentax DSLR in outdoor daylight conditions I always have D-Range Highlight Protection turned on, in which case the normal base ISO is then 200.

Cheers.
Philip

[Kerrowdown]

what is best ISO setting for outdoor use?

As already suggested... the lowest you get away with, while still achieving the result you want or need.