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Do not know what this denotes i.e. "Use ISO 100 whenever possible".
Making a quick guess does it have anything to do with Lense Aperture ?
Many thanks for the link....have added it to my Favorites for study.
The reason for using ISO 100 on digicams is to prevent noise (grain). Just about all digital cameras have problems with noise, more so compacts.
Interesting, cool article, made me chuckle.
ISO is the measure of 'Film' speed based on the emulsion
This measure has carried over Digi cameras.
Essentially the lower the number the finer the grain[noise] but lower speed[sensitivity- not so good in low light]
The higher the ISO number the more light sensitive, can see dimmer images but the trade off is a higher 'grain[Noise]
Grain meant in film days the size of the Silver crystals in the film emulsion that registered the light
the bigger they were the more light they captured- but showed up more in the finished result
and Lower fine grain -less capture ability therefore 'saw' less.
All Ditto the the sensitivity to to CCD's
The slower the speed of film the more detail that was available, especially useful when making big enlargements.
The faster the film speed the more the detail (in relative terms) that was lost; however, for many types of photography such as night work, sports etc the loss of detail was less important than getting the required shots.
It appears to me that Digicam makers quote high pixel rates in order to attract buyers.
However if the camera has a small sensor, then this increases the 'noise' at high ISO settings.
For detailed close-up shots then you would have to set at the lowest possible ISO setting. Otherwise you will have blurring at the edges.
I am no expert (as you have probably gathered) but this appears to be the general consensus on the various reviews I have read.
So basically if a camera has a high rated pixel count, it is meaningless unless it has a good sensor !
higher pixel counts means that a picture can be enlarged more. if you think about old film then they were given an aa or iso rating. most people who used colour film used either 100 or 20 asa/iso they gave good results. the higher the number the faster the film so you could use it in lower light conditions, the down side was the picture quality was degraded. to take a picture you need to get light into the lens if you look at a 35mm lens its is big lets lots of light in. now compare this with a compact digi you can see that the amount of light that lets in is greatly reduced. i have just got a new camera and i have gone for a canon a640 which isnt the smalest around but also not as large as a dslr it is a compromise, i now have a lot of manual control over the picture including iso but what i said before large iso more noise if in doors then use a flash.
A lot of compacts have F/2,8 aperture just the same as a lot 35mm or DSLRs, so the amount of "light" hitting the sensor is just the same, assuming the shutter speed is the same.
Your Canon A640 has an f/2.8 lens, so the amount of light reaching the sensor at any given shutter speed is equal to the amount of light hitting the sensor of my Canon 30d with it's "35mm" f/2.8 L lens at the same shutter speed.
Extract from the following link.
click here Apertures
To allow us to use compare lenses and exposures, the apertures are measured and calibrated in terms of relative apertures. Any lens set to the same relative aperture will let the same amount of light reach the film under the same conditions. Relative apertures (also called f numbers) follow a series related by the square root of two (1.41…..):
1 1.4 2.8 4 5.6 8 11 16 etc
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