Why does my ISO only go down to 100?
Discussion
Bit of a random one but bear with me 
I *think* I am correct in saying that ISO100 is the minimum on most modern DSLRs.
But wouldn't it be useful to be able to 'turn down' the sensor to (say) 50 or even 10 if you wanted a long exposure - no crapping around with ND filters or Big Stoppers and the like, no colour cast, no need to attach filter holders etc, it would be great! We seem to have higher and higher ISOs available but why not lower ?
Just a thought
I *think* I am correct in saying that ISO100 is the minimum on most modern DSLRs.
But wouldn't it be useful to be able to 'turn down' the sensor to (say) 50 or even 10 if you wanted a long exposure - no crapping around with ND filters or Big Stoppers and the like, no colour cast, no need to attach filter holders etc, it would be great! We seem to have higher and higher ISOs available but why not lower ?
Just a thought
Only the 5D and 1D's (I think) have ISO 50. non of the crop ones do.
Its not a real ISO 50 either, but more like H1 H2 etc where it will over expose and cut the exposure back in processing, and you will loose some dynamic range for it.
As to why, its something to do with the physical photo sites/ADC's etc, and remember ISO is a moving target somewhat, according to DXOmark ISO 100 is usually 120-160
I dont know why we dont have lcd ND filters built into SLR's as yet, its in some P&S (though thats more to combat poor high shutter speeds than anything else..)
Its not a real ISO 50 either, but more like H1 H2 etc where it will over expose and cut the exposure back in processing, and you will loose some dynamic range for it.
As to why, its something to do with the physical photo sites/ADC's etc, and remember ISO is a moving target somewhat, according to DXOmark ISO 100 is usually 120-160
I dont know why we dont have lcd ND filters built into SLR's as yet, its in some P&S (though thats more to combat poor high shutter speeds than anything else..)
I would be interested to kn ow if there was any fundamental difference between shooting at the 'fake' ISO 50 and shooting at ISO 100 and overexposing a stop then pulling back in post.
Wonder if ISO 50 would hold any more detail in the hilites? I dont see why it would but there may be more to it than purely manipulation of the sensor data (ala h1/h2).
Wonder if ISO 50 would hold any more detail in the hilites? I dont see why it would but there may be more to it than purely manipulation of the sensor data (ala h1/h2).
This :
Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user "ISO" setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes. Because the 1998 version of ISO 12232 did not permit measurement of camera output that had lossy compression, it was not possible to correctly apply any of those measurements to cameras that did not produce sRGB files in an uncompressed format such as TIFF. Following the publication of CIPA DC-004 in 2006, Japanese manufacturers of digital still cameras are required to specify whether a sensitivity rating is REI or SOS.[citation needed]
from http://en.wikipedia.org/wiki/Film_speed#Digital_ca...
Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user "ISO" setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes. Because the 1998 version of ISO 12232 did not permit measurement of camera output that had lossy compression, it was not possible to correctly apply any of those measurements to cameras that did not produce sRGB files in an uncompressed format such as TIFF. Following the publication of CIPA DC-004 in 2006, Japanese manufacturers of digital still cameras are required to specify whether a sensitivity rating is REI or SOS.[citation needed]
from http://en.wikipedia.org/wiki/Film_speed#Digital_ca...
jarvie said:
I don't know what Canon's are like (s
te 
) but on my Nikon ISO 50 is down as low 1, I don't kow why, it just is :S
Because it's not actually ISO 50. It's ISO 100, but the sensor overexposes by one stop then reduces the brightness of the resulting image by one stop. The result is that you get something similar to ISO 50, but with reduced headroom to avoid blowing the highlights.te ) but on my Nikon ISO 50 is down as low 1, I don't kow why, it just is :SGassing Station | Photography & Video | Top of Page | What's New | My Stuff