Author Topic: Infinity focusing in the dark  (Read 73 times)

1022mm

  • Newbie
  • *
  • Posts: 7
    • View Profile
Infinity focusing in the dark
« on: March 15, 2019, 03:58:50 PM »
I'm a new Chronos user that will be doing some outdoor shoots this spring and summer.  Some at night (things like fireworks and hopefully some lightning strikes).   I'm using mainly Canon lenses with a EF-mount to C mount converter.

I've done a few trial runs at night, and I'm running into some difficulties with focusing.   Low-light scenes don't show up with enough clarity to focus using the Chronos LCD screen.   With my DSLR, I can get a nighttime infinity focus lock using things like distant streetlights and car lights, these are things that understandably won't show up at all on the Chronos LCD.  I have an external monitor on order, but I'm assuming it won't show much either.   I've tried getting a focus lock using my DSLR, then moving the lens over to the Chronos without any success.  I've also tried doing a daylight focus at infinity, then marking the focus ring on the lens for later.  The problem is that some of my lenses' focus rings are electronic without hard stops, meaning that marking the ring at a certain position doesn't guarantee that the internal focusing mechanism will actually be in the same position later.

Would it be possible to adjust the Chronos backfocus to exactly match my DSLR? That way I can focus a lens using the DSLR, then transfer it to the Chronos.   Right now that's my best idea, but wondering if anyone else had any other methods that have worked for you.
« Last Edit: March 15, 2019, 04:03:52 PM by 1022mm »

nik282000

  • Jr. Member
  • **
  • Posts: 70
    • View Profile
Re: Infinity focusing in the dark
« Reply #1 on: March 15, 2019, 04:17:52 PM »
If you set your Chronos to 30fps you can increase the exposure enough to let you focus. After you set the focus put the framerate back up to what you intend to record.

1022mm

  • Newbie
  • *
  • Posts: 7
    • View Profile
Re: Infinity focusing in the dark
« Reply #2 on: March 16, 2019, 02:52:52 PM »
Thank you very much, that is tremendously helpful!  I had to really crank up the exposure to get the distant lights to show up, but that definitely worked.   I'm sure it will be even easier with the external monitor. Thanks again!

Martin

  • Newbie
  • *
  • Posts: 22
    • View Profile
Re: Infinity focusing in the dark
« Reply #3 on: March 16, 2019, 07:29:04 PM »
Hi,

also, don't use fullframe DSLR lenses with simple mount adadpters :)

You'll lose A LOT of light that way. You'll just illuminate the area around your sensor.. ;)
I started like that as well, but, for example, speedboosting lenses more closely engineered to your sensors dimensions (iirc it's a ~2/3" sensor or ~8.5x6.5mm) like MF43, Nikon1, Pentax Q(?) OR using native C/CS-mount lenses will make things quite a bit brighter :)

You can get good, not too expensive, f/0.95 native lenses for CS-mount, I paid 190 Euros/~214 USD early last year for a Schneider Xenon 25mm. Image quality improved simply because of more light hitting the sensor!

Have fun!

1022mm

  • Newbie
  • *
  • Posts: 7
    • View Profile
Re: Infinity focusing in the dark
« Reply #4 on: March 16, 2019, 09:08:46 PM »
I bought the Computar (kit) lens with the camera, but have found it to be quite soft at the wide end.   I'll check out some of the C-mounts to see if there is a better wide-angle option than my 10-22mm, which so far seems to work OK with sharpness over the whole image.