Understanding Lumix G9 Starlight AF

[GrayCard]

Panasonic's documentation in any available G9 manuals is scant and uninformative, at best, when it comes to the Starlight AF function. I have done considerable experimentation to develop a reliable procedure to get Starlight AF to work, and to understand not only the "how", but the "why", as well. It starts with understanding how this function works. I found an article on Panasonic Australia's blog site that was quite enlightening.

From: https://blogs.panasonic.com.au/consumer/top-tips-for-astrophotography-with-lumix/.

Starlight AF

Focusing on low-light subjects can be extremely tricky in any scenario. Astrophotography is no exception, with a photo of the night sky that is even slightly out of focus likely to lose its dramatic appeal. For decades, manual focusing was the only technique to focus a camera when shooting astro, leading to the misconception that manual focus always delivered the sharpest results. Starlight AF challenges this belief, delivering real world results to back up its capability. Equipped in LUMIX cameras such as the S5, GH6, GH5M2 and G9, Starlight AF temporarily ramps-up the ISO to create a brighter scene giving the AF system more information to be able to successfully lock focus and ensure your stars are pin-point sharp.

Here's how to invoke the process:

Engaging Panasonic Starlight AF:

1. The camera should (optionally) be mounted on a tripod for stability in long exposures with image stabilization turned OFF when using a tripod.
2. Set AF to AFS, AFF or AFC.
3. Place the AF box in the center of the viewfinder or monitor.
4. Visible stars need to be located within the AF box.
5. Half-press and hold the shutter release (or cable release) to activate the LOW indicator ~2 seconds after the shutter button has been half-pressed and held, presuming that one is in a low-light situation.
6. Once the LOW indicator is showing in the viewfinder or monitor, continue half-pressing the shutter release (or cable release) to activate Starlight AF if a detectable star is inside the elevated ISO sensor area.
7. If there is no star subject matter visible inside the elevated ISO sensor area, four box corners delineating the elevated ISO sensing area (approximately half the area of the viewfinder or monitor) should appear in the viewfinder or monitor 4-10 seconds after the shutter button has been half-pressed and held, depending on the focal length of the lens in use. The box corners will be red indicating that focus is not achieved.
8. When the camera finds star subject matter within the sensing area, the four red box corners will turn green indicating that focus has been achieved, and the STAR indicator will be visible.
9. Once the desired subject is within the green box corners and the STAR indicator has activated in the viewfinder or monitor indicating that is is in focus, fully press the shutter button.

Look for these indicators (Courtesy of Panasonic Customer Service):

• Red blinking exposure values > proper exposure is not achieved
• Red square/blinking green dot > focus is not achieved
• Green square/solid green dot > focus is achieved

Notes:

1. Half-press does not work from the Lumix Sync app.
2. Half-press has been mentioned above, but Back Button Focus, AF ON: Far Shift and AF ON: Near Shift will work as well, and must be fully pressed and held down until STAR appears.
3. Note that the lens focal length may affect the length of time to see the green box corners as it increases, but in any case, maintain the shutter half-press until the green box corners appear, and continue the half-press until STAR appears.

 

[jrsforums]

Nice piece of work. good information. Thanks

 

[tpani]

Two nights ago I tried using Starlight AF, unsuccessfully.

Questions:

1. You write about "AF box". Does this imply a specific AF mode, or will any AF mode do?
2. IBIS being off is not required to trigger Startlight AF, or is it?

My G9 shows the green ball and "Low", but would not show "Star". On most attempts it would not confirm focus to anything, but a couple of times a small green rectangle would appear, and the shutter would be activated. But this was not due to Startlight AF, I presume.

 

[GrayCard]

Thank you!

 

[GrayCard]

1. I've been using the 1-Area mode, and I vary the size and placement of the AF box according to the subject matter to make it as tight as possible to give the software the best possible chance of getting it right. Other AF modes will work, but only in the area of the reduced-size central box (roughly half the size of the viewfinder or monitor). Panasonic is very clear that Starlight AF will not work in the edge area of the framed shot.

2. Since I'm always using a tripod for this kind of work, I make sure that IBIS is off to prevent it conflicting with the stability of the tripod. As for shooting astro hand-held, forget about it. Light is very scarce in this instance, and the camera is working very hard to find a subject and focus on it. I'll be the first to admit that I can't hold the camera steady enough in low light to guarantee a well-focused shot. To answer your question, IBIS is NOT required to activate Starlight AF.

 

[loafer]

I just went through this exercise and experience in a nice dark sky area

The Panasonic 9mm did not work. It never showed 4 green corners, they remained red. So I resorted to manual focus - which has reliably been where the far focus mark is on the display and this is also where the camera gets set at when you use the lens release switch.

The 20 mm lens did a nice job focussing when it reach the low focus - but no stars were lit up.

There were no planets easily visible from my location. But the Big Dipper stars are pretty bright so you would think they would activate the star function.



There was a minimal aurora the night with the 9 mm. Big Dipper in lower field - so a mostly N view (9mm).





A couple nights later, view of Milky Way in the SW (20 mm)







I am actually happy with the 20 mm shot. The 9 mm lens is very weak wide open on the left - which represents the black foreground in the first shot.

 

[GrayCard]

I'd suggest that Starlight AF was overcome by the relatively strong light from the sunset on your first photo. I've had the same issue when encountering light pollution from a nearby city. Another thing I noticed was that you're getting star trailing to a minor extent. I'd suggest that you use the NPF tables as a reference, and possibly drop your shutter speed to 8-10 seconds to eliminate the trailing, and up your ISO to compensate, but not over 3200 or you'll get noticeable noise.

 

[loafer]

I read your post a couple weeks ago in the other thread. Every was set up appropriately to the best of my ability on my G9. The rear screen was in night mode so I could maintain my night vision. The 9 mm never was able to get to 'LOW' with 4 green corners. It stopped with 4 red corners. Maybe if there was a planet or one of the very bright stars it would work - but then they should call it 'planet light' not 'starlight' focus.

The other shot was a very dim aurora, neither light pollution nor sunset. In all directions the 9 mm Lumix would not confirm focus in the dark. This was manual focus. Here is the west view

 

[GrayCard]

In night mode, it is very difficult to see the green corners. Best to watch the focus indicator. If it's solid, it's focused OK; if it's blinking, it is not focusing. That said, look back at your first photo. Remember the positions of the red box corners. The camera does not see (for the purpose of Starlight AF) anything outside of the delineated box. There are stars present, but the brighter ones are outside the box. On top of that, there is the sunset adding perhaps too much light for Starlight AF to work. I'm still experimenting with Starlight AF here, and the weather has been most uncooperative for the last six weeks or so. Tonight is going to be another overcast one, but Wednesday through Friday are predicted to be clear. I'll believe it when I see it...