Thursday, January 6, 2011

Nikon D70 sync speed tests

I got the Nikon D70 that I bought from ebay. Fortunately it looks to be in decent condition, albeit missing the rubber eyecup and LCD protector, and my lens mounts much less smoothly than in any of my previous cameras.

My purpose for the second body was to avoid having to switch lenses.  However, I also found the sync speed capabilities of the D70 intriguing.  I wasted no time in testing the sync speed. I'm happy enough with the native 1/500 limit but I was curious about the higher sync speeds made possible by the D70's hybrid shutter.

ABOUT THE HYBRID SHUTTER
DSLRs use a mechanical shutter.  Above the sync speed, the front and rear curtain form a slit that never exposes the sensor fully at any given time.  The result is that if flash is used, the front or rear curtain will partially block the flash.

On the other hand, point and shoot cameras have no mechanical shutter.  Instead, when you set the shutter speed, the sensor becomes active for that duration.  With this design, the camera theoretically has no sync speed limit (instead, flash duration becomes the limiting factor).  

The D70 is a DSLR with a hybrid shutter.  It has a mechanical shutter like other DSLRs but above the D70's mechanical shutter speed limit, the sensor acts like a point and shoot sensor and emulates higher shutter speeds by taking shorter samples from the sensor.  The issue with hybrid shutters is that the sensor is physically exposed for a longer duration than the shutter speed you choose.  If there is a very bright light source, that light will continue to shine on the sensor and overload it, causing "sensor blooming."  The shot below is an extreme example of sensor blooming (it was an SB-800 firing at point-blank range at the side of our bed).  Note that in addition to the bloom visible on the bottom right side of the frame, the wood floor now looks green.

Notwithstanding the sensor blooming issue, the very high sync speed of hybrid shutters can be very useful.  It's why the D70S (the updated version of the D70) was David Hobby's primary camera at least for a time.  On to the tests...

RESULTS OF SYNC SPEED TESTS:
  • TTL flash (SB-800) on-camera: 1/500 (no HSS / Auto FP sync)
  • TTL flash triggered via CLS: 1/500 (no HSS / Auto FP sync)
  • Manual flash (YN-560) on-camera: 1/8000
  • Manual flash (YN-560) off-camera, triggered wirelessly via Meike MK-RC7 radio trigger: 1/800. Note: At higher shutter speeds, no flash at all is recorded.  It appears that the RC7's radio trigger electronics are not fast enough to transmit the trigger signal above this speed.
  • Manual flash (YN-560) off-camera, connected via PC cord via Meike MK-RC7 transmitter: 1/8000
  • Two manual flashes - YN-560 on-camera and SB-800 triggered optically via SU-4 slave mode: 1/8000.  However, the shot has strange artifacts on the camera's LCD.  Upon import into Lightroom, the image looks normal.
  • Two manual flashes - YN-560 off-camera via PC cord and SB-800 triggered optically via SU-4 slave mode: 1/8000  .  Same issue with the artifacts as above.
I'm curious to see how useful this ultra-high sync will be in the real world.  Looks like the YN560 will earn a place in the camera bag :).

OTHER OBSERVATIONS ABOUT THE D70
Coming from the D80 and D300, I had fairly low expectations for this 7-year old camera.  Here are some of the things that stuck out to me:
  • The controls for reviewing images (zooming in, moving to the next image, etc.) are very cumbersome and will take me a lot of getting used to.  Due to the poor controls and the small 1.8" screen, confirming focus takes a while.
  • The advanced wireless lighting is quite primitive.  It can control only one group and the popup cannot contribute to exposure.  Actually I was aware of that.  What I didn't know was that there was only one channel (channel 3).  Fortunately I've never seen anyone else use off-camera flash - even once.
  • The TTL flash metering accuracy is noticeably inferior to that of the D300.  One of my test shots with bounce flash was more than 2 stops underexposed.  With this camera, I will be watching the histogram much more carefully.
  • The menu has no option for reversing the dial direction and the light meter direction.  To avoid confusing myself, I have to change my D300 settings back to the direction being used in the D70.
  • On the positive side, the 1600 ISO was usable.  In fact even when pushed 2 stops over, the image is still usable (after noise reduction in Lightroom) and most of the noise is grain-like luminance noise not blotchy chroma noise.  I'm amazed about the ISO noise given that it's a 7-year old sensor.
  • Due to the relatively low 6.1 megapixel resolution, I won't have much room for cropping therefore I will pair this with my tele zoom (Sigma 50-150).  I'm pairing the D300 with my standard zoom (Tamron 17-50 VC).