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800 ISO - Effects what?
I had my Canon 400D set to 800 ISO while using my 50mm 1.4 portrait lens. I took some great portaits today and want to print them. They look impeccable. Crisp everywhere they should be and great bokeh. What role does this 800 ISO play? I normally leave it at 100 or 200..

Many thanks!!..

Comments (7)

As you go up in iso from 100-200-400800-1600-3200, the more sensative to light the sensor becomes. it lets you shoot a higher shutter speed than you normally would or higher fstop. if you have a situation that at 200iso you have 1/60sec(and 1/60 will not stop the action) at f8.0 and you cannot change the fstop because you donot want any less dof. then the answer is to up the iso to say iso 800. with the above situation the shutter speed is now 1/250sec and you can stop your action just fine..

Or you are shooting in a dim hall and you have iso 200 and 1/15sec and f2.8(wideopen lens). the shot would blur. up the iso to 800 or 1600, and your shutter speed becomes 1/125 and 1/250 respectively..

I hope this answers your question...

Comment #1

The above reply explains how ISO changes the exposure, ie there are three things that you can adjust on the camera: Shutter speed, apature and ISO..

Is that what you wanted to know or did you want to know more about what's happening when you up the ISO and the downsides to shooting at high ISOs?A member of the rabble in good standing...

Comment #2

BobbieWithCamera wrote:.

I had my Canon 400D set to 800 ISO while using my 50mm 1.4 portraitlens. I took some great portaits today and want to print them. Theylook impeccable. Crisp everywhere they should be and great bokeh.What role does this 800 ISO play? I normally leave it at 100 or 200..

It has been my experience that at ISO 800 you may loose some color when shooting outdoors in low light with no supplemental lighting (Like a flash, street light, etc..). With supplemental lighting in low light situations I have found ISO 800 to work very well..

FINE PRINT: I reserve the right to be wrong. Should you prove me wrong, I reserve the right to change my mind...

Comment #3

The downsides to shooting at such a high ISO is where I was going with it. Thats what I need to know. I didn't intentionally shoot at 800. Thanks to all who replied. Some was a little hard to follow but I'll slowly get it.  .

LM1 wrote:.

The above reply explains how ISO changes the exposure, ie there arethree things that you can adjust on the camera: Shutter speed,apature and ISO.Is that what you wanted to know or did you want to know more aboutwhat's happening when you up the ISO and the downsides to shooting athigh ISOs?A member of the rabble in good standing...

Comment #4

When you increase the ISO you are increasing the gain (amplification) applied to the signal from the sensor. if you are shooting in low light, obviously not much light hits the sensor, so the electrical signal it generates is small. To get it up to 'normal' levels you simply have to multiply it up. So a sensor at ISO800, correctly exposed, will have only one-eighth as much light hitting it as the same sensor at ISO100, so the output needs to be multiplied by 8 - which affects the signal and the random noise equally..

The good thing about this is that you can take pictures in light that is much weaker. the down side is that amplifying a weak signal introduces noise. Imagine taking a small radio and turning the volume up full; you'll get a loud sound but a lot of hiss too. The small radio wit hthe volume turned up to 10 might produce the same volume as a bigger and better radio turned up to 3, but the quality of the sound will be poorer..

The result in a camera is an increase in noise, which manifests irself in a speckly appearance when you look closely. Areas of the picture that should look exactly the same (e.g. adjacent pixels on a blue sky) will not be exactly the same because the random noise has been amplified along with the signal..

If you expand your pictures at ISO800 on the computer screen up to 100% (or more), and look at the pixels in shadow areas, you will see a lot more speckle than you would at ISO 100. of course at ISO 100 you would have needed a shutter speed eight times longer which means you might not have got the shot in the first place..

So there is a tradeoff: high ISO allows you to take pictures in low light without a flash BUT the image quality starts to suffer. I use ISO 800 regularly on my Pentax K100D and the results look fine printed at 10 x 8. ISO 1600 looks considerably worse and I would use this only for emergenices or if I didn't intend to print the picture bigger than 6 x 4. I think this is about the state of the art at the moment: on most DSLRs I have read reviews of, ISO 800 looks fine but 1600 is a big step down in image quality. In general use the lowest ISO setting you need to get a shutter speed short enough to prevent camera shake - then you will gat a picture that is both sharp and has minimal noise..

Best wishesMike..

Comment #5

BobbieWithCamera wrote:.

The downsides to shooting at such a high ISO is where I was goingwith it. Thats what I need to know. I didn't intentionally shoot at800. Thanks to all who replied. Some was a little hard to followbut I'll slowly get it.  .

Well, the noise issue has been discussed..

As well when you up the ISO you get a decrease in Dynamic Range. Thus the difference between the brightest and darkest areas of the picture have to be closer together (exposure wise) or one or the other (or both) will be clipped. (Clipped is when the value in any given pixel has hit the limit, either 0 or 255) For most portraits this is not a problem but with outdoor photography on reasonably bright days it can be a real issue..

As well when you up the ISO you decrease the total number of electrons in the well (pixel well). For instance at ISO 100 when the well is full to saturation from a bright area of the picture it will be at a value of 255. When you run the ISO up to 200 the well is declared saturated (255) when it's only half full of electrons. At ISO 400 it's only 1/4th full. So at ISO 800 it's only 1/8th full. (This is amplification.).

So at ISO 800 you are compressing all your tone values into a very small space and start to get errors. This shows up as a kind of blotchy look to some smooth areas..

Different cameras handle these physical issues differently in software so the effects are different in amount and quality but will jump up and bite you when you least expect it..

I make a point of reseting the camera to ISO 100 before shutting it down after a shoot. Many cameras have a menu item that will reset to predertimed defaults, use it if you have it.A member of the rabble in good standing...

Comment #6

BobbieWithCamera wrote:.

I had my Canon 400D set to 800 ISO while using my 50mm 1.4 portraitlens. I took some great portaits today and want to print them. Theylook impeccable. Crisp everywhere they should be and great bokeh.What role does this 800 ISO play? I normally leave it at 100 or 200..

Many thanks!!.

As most have noted, the thing that happens as you increase ISO is that the picture quality decreases. What saves you is that on your Canon, it's barely noticeable. What probably happened is that your lens stayed reasonably wide open, like f/2.8 or something, and your shutter speed went way up to keep the exposure correct..

So what you might be liking is the freedom from motion blur you got from the high shutter speed..

Leonard Migliore..

Comment #7

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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