Thursday, December 11, 2014

ND Throttle Testing with the A6000

It has been just over a week since I acquired the Sony A6000 ‘system’. The camera is clearly a major departure from my normal gear, eg full frame vs cropped, SLR vs mirrorless, and large vs small! 

I’m stuck at home for a day or so to ‘recover’ from a molar extraction. So a chance to carry out some A6000 experiments.

One reason I was attracted to a mirrorless system, of any kind, was the chance to play around with a variable ND filter (2-1000) that works with a wide angle lens.I have ND filters for my 5DIII lenses, but not a variable ND, as these tend to fall over with wide angle lenses; giving you that horrible X effect in your image: which you can not take out in post. The Vizelex ND Throttle Lens Mount Adapter from Fotodiox Pro allows me to connect my EOS lenses to the Sony A6000 APS-C camera.

Having experimented with the set up today, I have settled on the following workflow (designed for long-exposure photography, ie the ND Throttle is also useful for ensuring a 180 degree shutter speed in videography) for the A6000 with my manual aperture Rokinon 14mm F/2.8:
  • First, ensure the Rokinon 14mm is set to the optimum hyperfocal distance, which, for a blur spot of 18 microns, accounting for the sensor and diffraction on the A6000 APS-C, is just under 6 feet at F/8: using TrueDOF-Pro. In other words, focus at 6 feet and your image will fall within your acceptable focus criteria from about 3 feet to infinity. 
  • Dial in the F/8 aperture on the lens (you will see F/00 in Lightroom as the lens is not electronically coupled to the camera: this missing EXIF data can be added back in later if required). 
  • Focus at 6 feet using the A6000 magnified LV focus screen and focus peaking. 
  • Compose.
  • Set the camera to manual mode and set the desired shutter speed (in this experiment I set the shutter to 15 seconds). 
  • Using LV with the histogram showing rotate the Throttle’s adjustment ring until the LV exposure looks OK, ie ETTR from the histogram and the ‘blinkies’. 
  • Trigger the shutter: I prefer to do this remotely and on this occasion did so through a cheap IR remote. 
  • In Lightroom correct the Rokinon 14mm’s barrel distortion: I use PTLens. 
  • Adjust for look, which in this occasion I didn’t bother doing. 
Here is the resultant 15s test image, ie the usual boring image of one of the rooms in our house.

Bottom line: if you wish to take long exposure images and use a wide angle lens, you really need to carry a set of ND filters with you, as variable ND filters, at the extreme setting, do not work very well (the dreaded X effect). By using DSLR lenses, in my case EOS EF lenses, on a mirrorless body, you are able to make use of the variable ND Throttle, which generates no X effect at wide angles.

No comments:

Post a Comment