ISO ?? - DPChallenge Forums

03/07/2005 05:55:50 PM · #1

Right now I dont even know what it stands for but I guess I understand its got something to do with sensitivity. Could someone elaborate please?

What I wanna know it why is there graininess at higher ISO settings and why is it not on lower? Also why do we need to use higher ISO? In what conditions?

Thanks

soup

Canon EF 17-40mm f/4.0L USM

03/07/2005 06:07:28 PM · #2

it has to do with the sensitvity of the film/sensor to light. the higher the ISO/ASA setting, the more sensitive the film/sensor is to light, but at the cost of quality of the image. grain/noise is more likely with a high ISO setting. one step up in the ISO is the same as a one stop wider aperture, or a one stop faster shutter speed.

in general the better the film quality, or the camera quality the less susceptible the image will be to grain/noise.

adjust the aperture and shutter speed first, and if you still can't get a good meter reading, try upping the ISO.

Message edited by author 2005-03-07 18:08:04.

sabphoto

Samsung Galaxy S8/S8+

03/07/2005 06:09:47 PM · #3

quick and dirty....ISO is the film speed in traditional film cameras.

here: //photography.about.com/library/weekly/aa122203d.htm
Sensitivity
Often referred to simply as ISO, this relates the sensitivity of the CCD or other sensor in the camera to film speeds. Most digital cameras work in the range from ISO 50 (slow film) to ISO 400 (fast film) with some going up as high as ISO 6400 equivalent. You will get best quality at the lower speeds. As you increase the sensitivity of the device, it picks up more random noise and the pictures get noticeably less sharp and pick up uneven patterns in tone and colour, especially noticeable in flat areas such as a blue sky.

Higher sensitivity does let you work in darker conditions without flash, and the results on the best digital cameras at ISO 1000 or 1600 can beat film hands down. Those I get at 6400 are more impressionistic than photographic.

Zap228

Canon EOS-300D Rebel

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

03/07/2005 06:19:45 PM · #4

On most dslr's and some other digital cameras it is adjustable, and usually the lower the ISO, the higher the quality or sharpness of the picture. Theres usually noise in pictures with a high ISO.

Natator

Canon EOS-5D

Canon EF 24-105mm f/4.0L IS

03/07/2005 06:29:07 PM · #5

I always shoot at the lowest ISO I can, which is typically 100 in daylight or studio controlled conditions.

I know in the old days you avoided ISO 400 35mm film for instance unless you specifically needed it for dark shots as the grain was quite obvious. I believe though that the film have got a lot better since then and it has become a more usuable ISO.

However .....

On the 20D I can't ever spot any noise at 400, even 800 usually.

So, is there realistically any advantage to shooting at ISO 100 over 400 I wonder now? If I can shoot at 400 with no loss of quality, then in effect I have (I think) made all my lenses the equivalent of 2 stops faster ...... someone please correct me if that logic is flawed.

03/07/2005 06:30:42 PM · #6

Thats another thing I noticed. Whenever I shoot at higher ISO I get a grainy image. So hows that good? I mean shouldnt we shoot at lower ISO all the time to avoid that grainy image?

I understand the dSLR's may be good at removing that noise? Am I correct? What about post processing? Is it possible to remove that noise there?

03/07/2005 06:34:57 PM · #7

Faster? ok here;s another doubt I have had for some time but never asked thinking maybe its too dumb. Doesent faster mean slower? I mean you can use a shutter speed slower due to high sensitivity (of ISO) ?

What does slower or faster mean?

Sorry again for the dumb q's

soup

Canon EF 17-40mm f/4.0L USM

03/07/2005 06:37:42 PM · #8

i would say that's correct.
but not so much as there is no loss of quality.

and film performs better at high ISO these days.

Originally posted by Natator:

So, is there realistically any advantage to shooting at ISO 100 over 400 I wonder now? If I can shoot at 400 with no loss of quality, then in effect I have (I think) made all my lenses the equivalent of 2 stops faster ...... someone please correct me if that logic is flawed.

Plexxoid

Canon EF 70-200mm f/2.8L IS USM

03/07/2005 06:39:17 PM · #9

Faster can mean higher ISO, fast shutter, or wider aperture. When you raise the ISO or widen the aperture, you are able to use a FASTER shutter speed.

Nikon AF-S NIKKOR 200-500mm f/5.6E ED VR

03/07/2005 06:47:33 PM · #10

Right, thanks

Now one more question, widen the aperture or decrease shutter speed? Which is preferred in case of adjusting the exposure for a shot? I mean which value one must adjust first and then compensate using the other? Cause and effect??

RulerZigzag

Nikon D750

03/07/2005 06:58:04 PM · #11

ISO is film speed.. Try to raise the ISO if you want to capture something constantly moving, such as a fish in an aquarium. Boost the ISO in low lighting conditions also.

The Shutter speed should be lowered if you want to blur a moving object or bring out light in dark conditions. You need a tripod when slowing down your shutter, unless you have a surgeon's steady hand.

Aperture is the amount of light being let into the camera. The higher the number the narrower the aperture.

Bran-O-Rama

Canon EOS-5D

Canon EF 24-70mm f/2.8L USM

03/07/2005 07:05:33 PM · #12

Since no one answered the original question (what it stands for), it's International Standards Organization.

Regarding the difference in adjusting the aperture or shutter speed, that depends on the intent of the shot. For action/sports, you'll want a fast shutter so most likely you'll be shooting Shutter Priority (Tv) and letting the camera adjust the aperture for you.

Aperture also affects the DOF (depth of field). 90% of the time, I shoot in Av (Aperture priority). Generally when shooting landscapes, you want a small aperture for an immense DOF to have everything in focus. Sometimes you'll need to open up the aperture a little if you are handholding to allow more light. You'll have to decide which is less detrimental to the photo: slight DOF blur, or blur from handholding a slow shutter.

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

03/07/2005 07:05:56 PM · #13

ISO = International Standards Organization. It's a film-based designation that's been adopted by the digital world to give a sense of relative sensitivity to light.

The higher the ISO, the greater the sensitivity to light. At a low ISO you need a wider aperture or a slower shutter speed to deliver the same relative exposure to the film plane. In film, the higher the ISO the grainier the film. This is because high-speed films use emulsions composed of larger grains of silver halides.

In the digital world it's not that simple, because the construction of sensors can be different from camera to camera. But in any given camera, as a rule of thumb, the "faster" the speed (the higher the ISO) the more noise the image will display, especially in the dark areas.

In general, higher ISO = coarser sampling.

Robt.

Message edited by author 2005-03-07 19:06:58.

jazzmik

Nikon D300

Tamron SP AF 28-75mm f/2.8 XR Di for Nikon

03/07/2005 07:30:16 PM · #14

Originally posted by bear_music:

ISO = International Standards Organization...

actually it's "International Organization for Standardization." Rather than using IOS, the organization derived its name from the Greek isos, meaning equal.

soup