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pauls314159

Questions re evaluating BYN and D810

Question

I'm evaluating BYN for use with my D810 and wanted to confirm answers to a couple of questions:

- I wanted to confirm that I CANNOT focus via software control (this is what I've seen in the forums, at least for older versions. Lens I am testing with is AFS 70-200mm II.) I'm actually seeing that it's easier to focus via Liveview using camera display as opposed to more conveniently angled laptop display because feedback to adjustments is quicker. Can anyone make any suggestions re BYN and/or camera settings to make feedback on laptop display quicker re focusing?

- I've been shooting with Delayed Exposure set to 2 seconds re mirror slap. Discussions on whether this is necessary for long exposures aside, when capturing an image sequence, audibly I believe I'm hearing a 2 second delay between mirror up and shutter open, but the exposure times I'm seeing recorded in the image files include the 2 second delay. Can  anyone provide any insight on what's going on here?

- Lastly, I believe this is wishful thinking, but for recording dark frames, I wanted to confirm I do physically need to cover the lens, correct? (ie camera interface does not provide a mechanism for recording frame with shutter closed to automate interleaving dark frame capture).

Thanks in advance for any answers!

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Focus via Software Control - NIKON does support it - Search of the BYN Forum finds uses of D800 and D500 and D7200 with success.  The higher-end NIKON DSLRs need to do several In-Camera changes such as selecting a "simpler Auto-Focus mode" than Face-Detection, etc.  And the Camera Body and Lens need to have AF=ON (not a problem for D810 and Newer Lenses) for Focusing, then AF=OFF /Manual Focus Switch before attempting an Exposure.

(There's decent detail deep in the BYN Forum)

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If you have an autofocus lens on the camera with the lens in AF mode, you should be able to drive lens in small increments from BYN. Then once critical focus has been achieved you need to tape the lens in place and switch it to Manual Focus so that the camera will not try to focus at the start of the exposure. At least this is how it works with my Canon. The advantage of using BYN, rather than the camera's LCD display for focusing, is that BYN measures the diameter of the stars and provides a numerical measure of how good your focus is (FWHM or HFD). LiveView frames are shown very quickly. I don't know how you could adjust any faster or better by using the small LCD display on the camera.

The 2 second delay in BYN's capture plan goes before the start of the first exposure in your capture plan. It is not a mirror up delay. BYN does not support Mirror up delay for any camera; at least according to the Camera Support Grid on this web site. I believe that the authors are working to try to support this feature. If you are doing long duration deep sky imaging then mirror lock is totally unnecessary anyway. Not sure where you are seeing exposure times that include the 2 second delay. Please explain.

The camera has no concept of a dark frame (except for Long Exposure Noise Reduction) and does not allow you to take dark frames by keeping the shutter closed. It is up to you to prevent light from reaching the sensor. This is usually accomplished by covering the lens, or removing the lens and replacing it with the body cap.

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Thanks for your response.

I haven't been able to get remote focusing working via BYN. I believe this is tied to a limitation of the Nikon specific drivers/functions exposed by the camera vs what Canon makes available. If a BYN user could confirm that would be helpful, but as I indicated, fully zoomed on a star @ 200mm, focusing via camera display in Liveview works well, particularly because the star's width on the camera display responds more quickly with adjustments to the lens' focus.

With respect to the 2 second delay, this is set on camera when setting up delayed exposure mode: with that set, when exposure is initiated (via shutter button or remote), camera lifts the mirror, waits the specified delay (two seconds in my case), and opens the shutter to begin exposure. When I do this via my Shutterboss, I'll set the shutterboss exposure duration for 2 seconds plus desired exposure length, and the exposure time recorded in the captured images EXIF data will show the desired exposure length. When I do this via BYN, it sounds like the camera raises the mirror, waits 2 seconds before raising the shutter, and then exposes the sensor. However, the exposure time recorded in the captured image EXIF data shows desired exposure length+2 seconds. 

I appreciate that mirror lock-up and exposure duration +/- 2 seconds are both somewhat academic wrt deep sky imaging, but I'm mostly trying to confirm I have a good handle on the interaction between BYN and the camera, plus I'm also trying to isolate an unknown source of movement in my rig.

The dark frame bit was wishful thinking...

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The lens buttons in BYN will only work for the Nikon Z6 and Z7 if my memory serves me right.  For all other models there is less than 10% it might work.

Out of the box, if you can't, it means that either your lens, or your camera body/model, or a combination of both, does not allow for it.  The motor is in the lens, so for it to work the lens must allow for external commands to move the focus motors, then the camera must allow a pass-thru of the commands, and finally the Nikon SDK must allow for it for your camera model.  It's a lot of "if" and for this reason it is very difficult to assess.

Regards,

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Thanks s3igell, properly setting focus area did it - I now have focus via software control on my D810 by setting focus area to S (single-point AF, Note it doesn't seem to matter whether focus mode is set for single-servo or continuous servo), camera body set to AF, and lens set to either A/M or M/A.

For what it's worth, I've also confirmed that BYN properly records exposure time when putting camera in Delayed Exposure Mode (and optionally Electronic Front Curtain Shutter) without having to add in the mirror up delay (ie setting exposure for 40 seconds and camera with 2 second delayed exposure after mirror up, BYN will send open shutter, camera will raise mirror and wait 2 seconds to open shutter, and then record a 40 second exposure). Note that I'm not posting this to trigger a discussion about whether one would want to worry about mirror lock-up.

Thanks for everyone's help.

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