Sunday, January 2, 2011

Base ISO vs. Sync Speed

I decided to get a Nikon D70, one of the few DSLRs that has a sync speed of 1/500 (point and shoots meanwhile don't have much to worry about sync speed, allowing sync at theoretically any shutter speed).

What's so important about sync speed?
As I was choosing the D70, I was reminded that the base ISO was 200.  Did having a 200 ISO (as opposed to 100 ISO) limit erase the ultra-high 1/500 sync speed advantage?  Actually, no it does not.

Here's Neil van Niekerk's explanation of the issue:

Put another way, at 200 ISO, your flash has 1 stop more range or can shoot at a 1-stop narrower aperture relative to 100 ISO, so that even though you may need to shoot at a narrower aperture at 200 ISO (as opposed to 100 ISO), the relative power of your flash (compared to ambient) won't diminish.

If you're looking for a camera with a very high sync speed, the ones I'm aware of with 1/500 sync speed are:
  • Nikon D70 - has a built-in flash commander for one group.
  • Nikon D70s - has a larger 2-inch LCD screen than the D70.
  • Nikon D50 -  sensor has less noise than the D70 or D70S, but is an entry-level Nikon with no rear dial, no commander mode, and no built-in focus motor.
  • Nikon D40 - also an entry-level Nikon; has an even better (lower noise) sensor than that of the D50.
Some Nikons have a flash mode that can sync at 1/320 (1/3 stop higher than their native 1/250 sync speed) while being more efficient than high speed sync:
Nikon D300, D300S, D7000, D700
Note: I don't know how this higher sync speed works nor do I know what the power loss is.


  1. Trying to contribute to your blog again.
    The faster (1/320 vs. 1/250) sync speed of FP shutter is possible because the curtain travels faster in those higher models. When you think about it, the fast shutter speed that you can obtain without the two curtains traveling together (i.e., x-speed) is the time it takes for the first curtain to clear the sensor. The x-sync speed cannot exceed that speed. For a faster shutter speed, the second curtain must start traveling before the first curtain completely clears the sensor. With a better, improved mechanical shutter, the curtains will travel faster and result in higher x-sync speed.

    1. Thanks! If it's due to the mechanical speed of the shutter, why isn't the 1/320 speed the sync speed? And why is it that there is a reduction between the 1/250 natural sync speed and 1/320 non-HSS speed? (I've since learned that the power loss is a little less than 1 stop, still better than the more than 2 stop loss from switching to HSS.)

      Best regards,


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