[JeffJS]

Right I need ISO explaining in a simpleton way. I understand 100 iso is good on sunny days but what about 200,400 etc. Sorry if this is a dumb question guys.

So would it be a good idea to try and use between 100 and 400 as a rule?

Set your camera to Sv mode (pg 89 in your manual), dial it around on a given scene and see which is the most acceptable for you. In general, the lower the better.

I suggest you find a book explaining exposure because until you understand that, you won't fully understand any of it's components (ISO, Shutter Speed, Aperture). Here is a website that gets pretty deep into it.

The nutshell of it is this (when you want to change the ISO)..

You've taken a photo at ISO100, f5.6, 1/100 sec that you're happy with except you think the shutter speed was too slow. You want to double it for some reason but keep the same exposure. You can accomplish that in one of two ways. First set your shutter speed to 1/200 then set your ISO to 200 -OR- set your aperture to f4. As far as lighting is concerned, your exposure will be the same. Now here's the rub. Let's say you're using the Kit (18-55) lens at 55mm which wide open, is f5.6. At 55mm you cannot Go to f4 so you must adjust the ISO to achieve your goal of a faster shutter speed and keep the same exposure.

Let's put a faster lens on your camera. One of my personal favorites, the Pentax M 50mm f1.7. You've taken a photo of junior, wifey, hubby (whatever the case may be) at f1.7, ISO 800, 1/100s. You nailed the focus on the eyes and you're happy with your focus and lighting, you don't want to use a flash, but the result is too noisy (or grainy) looking for your taste. You want to reduce the ISO in this case. Set it to 400 which cuts your exposure in half. Your lens is already at f1.7 so you cannot open the lens any further to compensate for the change in ISO with aperture. Now to get your exposure back, we would cut the shutter speed in half to 1/50.

One universal truth about photography is this. It requires light. I don't care if you're using a phone camera or the most expensive dSLR money can buy. Where ISO noise is really going to become an issue is in shadows and dark areas of your photo. You can process some of it away but that comes at a cost of lost detail. What most noise reduction programs do is blur the noise so it cannot be seen as easily (simply stated). If you have enough light, you can go all the way to ISO 1600 in your K200d with little trouble. If you are trying to take a photo of a black dog, in a dark room, and try to push the ISO, you will likely end up with an unusable photo. I mentioned post processing because one of the ways of recovering a photo is to change the exposure, adding fill light, etc. What will happen if you've underexposed too much is that you will not be able to retrieve a photo, with enough detail, to call it a decent photo. The lower your ISO, the longer your exposure times will be required in a given scenario (at a fixed aperture, for example).

One of the best ways to learn is by doing. I would encourage you to put a static object on a table, with room lighting, and play with the information above to see the effects of changing the different exposure parameters.

Clear as mud, Right?

[cats_five]

www.dpreview.com did an in-depth of the K200D and this page and the next one show the results in their standard way. it shows most graphically how noise increases with ISO.

Pentax K200D Review: 15. Photographic tests (Noise): Digital Photography Review

[Ira]

We sometimes forget how what we consider a simple concept really isn't.

Four, a higher ISO lets you use a faster shutter speed (which lets in less light than a slower shutter speed), OR allows you to use a smaller F stop (which lets in less light than a larger F stop).

Or both.

You have to decide first:

1) "Wow! Plenty of sun today! I'm gonna keep the camera on 200 ISO for the least noise and best image quality!" (200 needs more light than 400, but you don't care. It's sunny, remember?)

2) "Look at this gorgeous flower! And gee, I love automatic mode! I'm in Av mode, I have my F stop set for F8, and the camera is giving me a shutter speed of 1/125! That shutter speed is plenty fast for me to handhold the camera, and that flower isn't doing much moving! Click! I got a great shot here!"

3) "Uh oh! Where did all those clouds come from? What happened to the sun? Damn! I still want to take more shots of that flower! But now it's giving me a shutter speed of 1/30, which is too slow for me to handhold since my hernia operation! Plus, the wind is moving the flower a little and 1/30 won't freeze it for a sharp picture! DAMN YOU NATURE! I want to stay at F8 for the better depth of field, but wait--all I have to do is change my ISO higher and see what I got. Let me try 400. HOORAY! It worked! The higher ISO allowed me to stay at F8, and is ALSO giving me a shutter speed of 125! GOD BLESS YOU PENTAX!"

4) "What's that!? They're robbing the BANK!!! And here I am with my camera! But those clouds are still here!!! And those guys are running FAST!!! I just need the shot! What to do!? What to do!? Wait--I remember what Ira told me! Let me set it for the highest ISO I have! Let me go to F4 to let in more light to be even safer. I don't care about noise in this image or even a little less depth of field, because I just want the shot to sell to the newspaper! CLICK! I did it! Perfectly exposed! I'm famous!

"But Ira deserves all the credit!"

[cats_five]

Here is a camera simulator that lets you see what happens when you change ISO, f-stop, and shutter speed.

Aperture, shutter and ISO value | SLR Camera Simulator

Tim

That is rathe good - the only thing it doesn't show is depth of field, but I know a website that does:

Online Depth of Field Calculator

[slip]

the best way I know how to explain ISO is this. picture looking at the photo on your camera's sensor. now imagine putting a magnifying between you and the sensor. the more magnifed it is (which equals to more ISO), the more light that hits the sensor but the more the sensors pixels are magnified. with a sensor the increased size of the pixels change to unwanted colors and or grain when the ISO is gets higher to make up for the lack of light in the scene you are capturing.
this isn't the way it works but the only way I can give you a visual representation of what ISO low to high is

hope this makes sense

randy

[cjbroadwell]

This thread has helped me to understand much more the relationships of iso, shutterspeed and fstop values..... Thank you!

[Mike Cash]

It's sort of like a see-saw....but with three ends instead of two. Imagine a three-pronged object such as you would get if you took a Mercedes-Benz logo and cut the circle off of it. Now, imagine that one is shutter speed, one is aperture, and one is ISO.

If you grip any of those three prongs tightly in your fist and then rotate it, the other two will move up and down in direct relation to each other. So if you grip the shutter speed prong (holding it steady) then adjusting aperture up means ISO goes down. Adjusting ISO up means aperture goes down. If you grip the ISO prong, then as shutter speed goes up aperture goes down (and vice versa). If you grip the aperture prong, then it is shutter speed and ISO which will move in relation to each other...one goes up as the other goes down.

Fortunately, all of these values (shutter speed, aperture, ISO) are designed to move in intervals of doubles and halves, which makes it very easy to work out the relation between them. A movement of one whole "notch" up on one is a doubling and a whole notch down is a halving. Just like in a real playground see-saw the ends always move by the same amount and in opposite directions. To maintain the same exposure you can adjust any of the three prongs in any direction you want....but you must adjust either one of the other two prongs an equal amount in the opposite direction.

So if you want a faster shutter speed (lets in less light with the shutter), then you need either a wider aperture (lets in more light) or a higher ISO (increases the sensor's sensitivity to light). If you want a slower shutter speed, then you need either a more narrow aperture or a lower ISO.

The ISO values are easy to understand: 100, 200, 400, 800, 1600, etc. Anyone can see that each is double the value in one direction and half the value in the other direction.

Shutter speeds are also easy: 1/15, 1/30, 1/60 etc. The same double/half relation applies.

It is aperture values that can be confusing, yet the same double/half relation applies here as well: f1.4, f2, f2.8, f4, f5.6 etc. The numbers look odd because they are a ratio of the size of the aperture opening in relation to the focal length of the lens. There's a good reason for expressing apertures in ratios rather than in the actual mm size of the opening, but it's not important right now.

What you basically want to do creatively with your SLR camera is to choose your shutter speed and/or aperture based on what you want to do with your picture. Do you want to stop motion? Or do you want it blurred? That affects which shutter speed you choose. Do you want as much as possible in focus? Or do you want to isolate your subject and have the foreground/background out of focus? That affects which aperture you choose.

So long as you are able to use the shutter speed or aperture that suits your purposes, the ISO should be kept as low as possible in order to minimize noise (unless you want noise). In lower light you might find that you can't get the shutter speed or aperture that you want. That is when you will need to increase your ISO.

Just keep in mind the three-pronged see-saw and remember that while any prong is held in position the other two move in relation to each other. And remember that "up" and "down" mean "brighter" and "darker" for our purposes here. Slower shutter speeds are brighter, while faster ones are darker. Large apertures (small numbers) are brighter, while smaller apertures (larger numbers) are darker. High ISOs are brighter, while lower ISOs are darker.

[newarts]

It's sort of like a see-saw....but with three ends instead of two. Imagine a three-pronged object such as you would get if you took a Mercedes-Benz logo and cut the circle off of it. Now, imagine that one is shutter speed, one is aperture, and one is ISO.......

Nice analogy Mike!

[Mike Cash]

Nice analogy Mike!

Thanks. It can be furthered by saying that the position of the center point represents a correct exposure. So long as you hold one prong steady and move the other two as mentioned above the position of the center point doesn't change. Now imagine that you hold two of the prongs in position and move the other one. The center must either go up or down, representing an overexposure or underexposure.

[newarts]

Thanks. It can be furthered by saying that the position of the center point represents a correct exposure. So long as you hold one prong steady and move the other two as mentioned above the position of the center point doesn't change. Now imagine that you hold two of the prongs in position and move the other one. The center must either go up or down, representing an overexposure or underexposure.

The three legs of the triple see-saw balance exposure in the middle. Increasing time on one leg raises exposure in the middle; one or both the other legs must be adjusted to compensate.

But there is more to it: the three legs of exposure have important photographic effects:

Speed <-> freezes motion/dims photo
F-Stop <-> increases depth/dims photo
ISO <-> brightens photo/adds noise

The three adjustments, "Shutter Speed", "F-Stop", and "ISO" could just as well be renamed "Motion Freeze", "Scene Depth", and "Photo Brightness".

With these new labels in mind the consequences of the photographer's choices are clearer.

An upward click of the depth control dims the photo by a click; compensation requires an upward click of the brightness control or a downward click of the shutter speed control, etc.

[JeffJS]

It also may be worth noting (to confuse things a little more) that with our in camera controls, each of these see-saw seats can be adjusted in 1/3 stops. Also worth clarifying that Mike's Double/Half is movement of a Full stop. Most lenses with aperture rings will adjust (with the aperture ring) in either full or Half Stops. That is, on some lenses there is a stop between say f5.6 and f8 that is f6.3 (but is not marked on the aperture ring).. Just to confuse things a little more . The rules still apply though. Movement of either of the three, requires an opposite movement of one of the others of the same amount.

[fourfivesix]

Some great advice guys thanks think its sinking in

[Ira]

It also may be worth noting (to confuse things a little more) that with our in camera controls, each of these see-saw seats can be adjusted in 1/3 stops. Also worth clarifying that Mike's Double/Half is movement of a Full stop. Most lenses with aperture rings will adjust (with the aperture ring) in either full or Half Stops. That is, on some lenses there is a stop between say f5.6 and f8 that is f6.3 (but is not marked on the aperture ring).. Just to confuse things a little more . The rules still apply though. Movement of either of the three, requires an opposite movement of one of the others of the same amount.

Good point. And to further confuse the OP, your ISO selections can be chopped to less than increments of 100% based on your Ev settings.

OP--forget I said that. You have enough to think about, but depending on your intital camaera settings, you can select 100, 125, 150, etc. ISOs also. It doesn't have to be 100, 200, 400, etc.

[Ira]

Nice analogy Mike!

I thought my bank robbery analogy was better.

[Mike Cash]

I didn't bother mentioning the 1/2 and 1/3 incremental settings because I was mostly interested in getting across the notion of the three settings' rigid link to each other and how they move in relation to each other. Once that principle is grasped the rest comes easy.

I am reminded of Dr. Milton Simmons, professor of Psychology, who contrary to popular practice would never tell students what questions would be on an upcoming test. He told us, "I teach principles. If you learn the principles, you don't have to worry what the questions are; you'll be able to answer them."

I thought my bank robbery analogy was better.

That's not an analogy; it's a scenario.

Let's look at it, though. Clouds are at most going to eat up three stops of light compared to a sunny sky and often only two stops, so Sunny 16 tells us that is going to be somewhere around f5.6 or f8....you're going on the safe side with f4. "Highest ISO" is going to vary according to camera, but let's say it is 3200.

You're adjusting for the dimmer light with opening up the aperture, so our Sunny 16 shutter value of 1/3200 remains constant for shooting at f5.6 if the clouds are eating up three stops of light. Opening up to f4 means we have to adjust our shutter speed to 1/6400....nice if you have a K5, but nothing else from Pentax shoots that fast. If the clouds are only eating two stops of light we'll need 1/12800, which not even the K5 is going to cover.

Similar situation even if we stipulate ISO1600. At f4 you'll get either 1/3200 on three stop clouds or 1/6400 on two stop clouds. Most newer cameras will handle the former, only the K5 will handle the latter.

Of course, the situation is different again if we're talking earlier in the morning or towards evening (irrelevant for banking hours....maybe useful for a gas station holdup), and also depends again on the time of the year. This sort of thing is why I don't like answers to questions about "What shutter/aperture/ISO setting should I use for situation xxxx?" which contain specific numbers. It is better for the person to learn the principles involved. That way when they spot the bank robbers coming out on a cloudy day, throw the camera to their eye and see what sort of shutter speed they're getting, they won't have to pause to think what to adjust and in which direction.