D90 ISO settings

[bs0604]

I read that in reference to low ISO settings 0.3, 0.7 and 1.0 translate to values of about 160, 125 and 100. What is the relationship between the first set of numbers and the second set?

 

[Rephargotohp]

1/3rd of a stop (from ISO200)

 

[bs0604]

thanks. Why did Nikon use ISO numbers throughout the range but at the extreme hi and low ends switch to fraction of stops?

 

[cnutco]

Because the International Organization for Standardization testing did not qualify the camera at either the very low or high end of the ISO settings. Therefore Nikon can not use the standard ISO settings for these extreems, if you will.

 

[KmH]

Which is why those are called 'equivelent' ISO values

The LO and HI equivelent ISO values are accomplished using software algorithms after the A/D conversion process, and result in a significant loss of image dynamic range. The normal D90 base ISO range of ISO 200 to ISO 3200 is accomplished using amplifier circuits before the A/D conversion process, so there is no loss of dynamic range.

 

[cnutco]

Which is why those are called 'equivelent' ISO values

The LO and HI equivelent ISO values are accomplished using software algorithms after the A/D conversion process, and result in a significant loss of image dynamic range. The normal D90 base ISO range of ISO 200 to ISO 3200 is accomplished using amplifier circuits before the A/D conversion process, so there is no loss of dynamic range.

Well, that sounds a lot smarter!

 

[KmH]

It expands on what you mentioned, and lets the OP know that there is an image quality penalty for using any of the 'equivelent ISO' settings.

The International Organization for Standardization (ISO) doesn't actually 'qualify' any cameras, they just write the specifications for the standards.

Film speed - Wikipedia, the free encyclopedia
The ISO 12232:2006 standardThe ISO standard ISO 12232:2006[SUP][53][/SUP] gives digital still camera manufacturers a choice of five different techniques for determining the exposure index rating at each sensitivity setting provided by a particular camera model. Three of the techniques in ISO 12232:2006 are carried over from the 1998 version of the standard, while two new techniques allowing for measurement of JPEG output files are introduced from CIPA DC-004.[SUP][54][/SUP] Depending on the technique selected, the exposure index rating can depend on the sensor sensitivity, the sensor noise, and the appearance of the resulting image. The standard specifies the measurement of light sensitivity of the entire digital camera system and not of individual components such as digital sensors, although Kodak has reported[SUP][55][/SUP] using a variation to characterize the sensitivity of two of their sensors in 2001.
The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily. The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used.
The Standard Output Sensitivity (SOS) technique, also new in the 2006 version of the standard, effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when the exposure is controlled by an automatic exposure control system calibrated per ISO 2721 and set to the EI with no exposure compensation. Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically JPEG—and not to output files in raw image format. It is not applicable when multi-zone metering is used.
The CIPA DC-004 standard requires that Japanese manufacturers of digital still cameras use either the REI or SOS techniques, and DC-008[SUP][56][/SUP] updates the Exif specification to differentiate between these values. Consequently, the three EI techniques carried over from ISO 12232:1998 are not widely used in recent camera models (approximately 2007 and later). As those earlier techniques did not allow for measurement from images produced with lossy compression, they cannot be used at all on cameras that produce images only in JPEG format.
The saturation-based technique is closely related to the SOS technique, with the sRGB output level being measured at 100% white rather than 18% gray. The saturation-based value is effectively 0.704 times the SOS value.[SUP][57][/SUP] Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically TIFF—and not to output files in raw image format. It is not applicable when multi-zone metering is used.
The two noise-based techniques have rarely been used for consumer digital still cameras. These techniques specify the highest EI that can be used while still providing either an “excellent” picture or a “usable” picture depending on the technique chosen.

 

[Rephargotohp]

Which is why those are called 'equivelent' ISO values

The LO and HI equivelent ISO values are accomplished using software algorithms after the A/D conversion process, and result in a significant loss of image dynamic range. The normal D90 base ISO range of ISO 200 to ISO 3200 is accomplished using amplifier circuits before the A/D conversion process, so there is no loss of dynamic range.

While it occurs, Whether that loss is "Significant is debatable

Because noise rises with ISO, There is a Loss of Dynamic range even using nromal ISO's in the case of the D90 it drops from 12.5 EV to 9.5 EV as you go from 200 to 3200. I'm sure that's what you meant to say

But you use what ISO you need when you need it

 

[cnutco]

But you use what ISO you need when you need it

I shot in a bball game in a gym that was built in 1958 at ISO 1600 with my D90 last week and it was terrible! I will have to put some SB900's in the stands next time...

Wish I could afford that full frame now...