Photography / Tips and Solutions

FocusEd: ISO Explained


In this week’s video, FocusEd discusses ISO. ISO is a measurement of a digital sensor’s (or films) sensitivity to light. This video goes into detail about when to use different ISO settings, as well as explaining native, standard, and boosted ISO for your digital camera.


ISO explained beautifully.  I am sending the link to my grandson who is just getting started in photography.  Kudos to B&H and Kelby for these presentations.  Keep up the good work, you guys are the best!

This was great. Excellent! It helped me to understand ISO very much.
Thank you!

vey well don. Thank you.

The presenter perpetuates a common myth; digital camera ISO is NOT a measure of sensitivity.  In the film days, ASA/ISO was a sensitivity metric, it described how sensitive the film was to light.  However, in todays digital cameras, ISO is a signal amplification metric, that is, it is applied to both signal and noise, it boosts the total signal PLUS noise.  The important distinction is the noise is also boosted along with the signal.  The signal is, "how much light" the camera is seeing, the noise is due to the dark current in the focal plane.   Thus when you boost the SNR you are ALSO boosting the dark current noise.  The bottom line, you are not getting something for nothing when you use higher ISOs.


I purchased a JVC LS300 camra from B & H and expect delivery 8/17/15. I am reading the manual and it is pretty overwhelming (might be easier with the camera in front of me). One feature it talks about is gain. I am assumimg this is like ISO. I think there is a setting on the camera that allows you to switched from gain to ISO (which I feel more comfortable with).  Also I read somewhere that the camera starts at ISO 400. What does this mean? What happened to 100 ISO?



Hi Vince -

The GAIN settings offered are from ISO400 to ISO25600.  These settings may also be displayed as dB:

For setting the gain value of each position on the

[GAIN] selection switch.

The setting is fixed at “AGC” in the Full Auto mode.

In addition, the sensitivity setting in Lolux is used.

[Gain] is set to “ISO”:

[Setting Values: AGC, ISO6400, ISO5000,

ISO4000, ISO3200, ISO2500, ISO2000,

ISO1600, ISO1250, ISO1000, ISO800, ISO640,

ISO500, ISO400]

(Default values GAIN L: ISO400, GAIN M:

ISO800, GAIN H: ISO1600

The JVC GY-LS300  Instruction Manual - Pages 98-99

Please contact us via e-mail if you have additional questions:

I read in one of Todd's articles a reference to "native ISO" and started to research it relative to a Nikon D5200.  While there was a lot of discussion of native vs standard ISO (mostly technobabble), I could not find any information as to the native ISO of specific cameras or groups of cameras (Nikon, Canon, etc.).  Since you can typically set ISO in increments of 1/3 stops, it seems it would be beneficial to know if your camera's native ISO is different from standard.