Author Topic: Playing with my new 20mm f/1.8S lens for the Z-mount  (Read 4885 times)

Macro_Cosmos

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Re: Playing with my new 20mm f/1.8S lens for the Z-mount
« Reply #30 on: June 21, 2020, 20:15:31 »
Ok.....I will look at the youtubes.......
Just a quick question. If you stack many pictures to reduce noise and you expose each 15-20 sec then stars "moves" a bit from frame to frame.
Is the stacking software able to align all these images so stars appears as single stars?   
I can see that from your images but just if I have understood it correct that if you have 16 images in the stack then the eposure of last image is about 16 x 20 sec. later.....or so.....?

My setup is a medium size carbon Gitzo tripod (old one) with only baseplate (center column removed) and head is a Foba Super Miniball (I agreed with myself that this was the most heavy I wanted to carry in the field).
I have a large Graf Studioball but it requires a tripod with larger baseplate. Both heads are with Arca Swiss mount.  The Graf ball-head is about 2 kg alone.....so not so transportable. Probably the reason they call it a Studioball. Don't know if the brand exist anymore.....but it is good quality.....so it may be used in the future but I will try first with the Foba setup. My only real wide angle lens for DX is the old Nikkor 12-24 DX zoom. My camera is a Z50.
Yeah they will move, hence you must tick auto-align.
Usually, PS does a good job in aligning. Sometimes it fails, which you have to do yourself. It's actually really easy and with experience, you'd be able to manually align many frames in minutes.
The images used will all have the same settings. It's not that important but it's more consistent.
Stacking won't transform into increased exposure time. Stacking 15 frames of 20sec exposures doesn't make it one frame of 300 seconds. If that's the case, trackers will be kind of pointless for astrolandscapes. Stacking lowers the ISO. The amount depends on the sensor and the such, so there is no formula. Stacking 20 frames of 15 seconds gives an ISO of... I'd say 500 on my Z6. Noise is all gone of course.

Longer exposures give you more stars as the sensor is able to pick up fainter ones. Yields higher image quality, you can use lower ISO, but you will see more hot pixels which is why dark frame stacking to subtract the hot pixels is important.
Here's what 3 minutes looks like:

Photo by a mate in SA: https://www.flickr.com/photos/130286344@N07/46341760424/in/dateposted/
Way more stars and detail.

I've never actually seen someone with the foba mini-superball before, it's expensive and looks pretty nice. It should work out nicely. Z50 with the 12-25mm would work out very nicely. You will be able to do 15-20 seconds. The Z50 lacks a shutter release input, but you can always use that bluetooth button or exposure delay mode which is what I do, can't be bothered to scuff around in the dark and expose my camera's port to humidity (it's winter here).

You can get PS at like $10 a month, it's bundled with lightroom. There's some very good astro freeware that does arguably a better job, I've yet to try out any though.
Photomicrography gallery: Instagram
Blog: Diatoms Australia
Andor Zyla 5.5 sCMOS | Hamamatsu ORCA-Flash V2 | Nikon Z6 | Olympus Microscope

MEPER

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Re: Playing with my new 20mm f/1.8S lens for the Z-mount
« Reply #31 on: June 21, 2020, 21:26:18 »
Thank you very much for the explanation. I will try it out using Z50 with either 12-24/4 or the 16-50 kit lens. It is 3.5 at 16mm. Kit lens is very light weight and should be well corrected wide open so this will be a good test of the lens.

The Foba Super mini is probably too expensive. I got it at a reasonable price many years ago. It works well with medium weight lenses and it can also support my old AF 300/2.8.

Erik Lund

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Re: Playing with my new 20mm f/1.8S lens for the Z-mount
« Reply #32 on: June 22, 2020, 10:50:55 »
The lone tree images works very nice! Thanks for sharing ;)
Erik Lund

Macro_Cosmos

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Re: Playing with my new 20mm f/1.8S lens for the Z-mount
« Reply #33 on: June 22, 2020, 17:45:33 »
The lone tree images works very nice! Thanks for sharing ;)
Thanks! I also fixed the gravestone one where there was obvious banding due to panorama stitching.
I noticed that the pic was no longer there, so fixed that too.
PS' vignetting correction doesn't seem to do a good job. For anyone using this lens wide open, +2 vignetting in capture one fixes the dark corners, LR has a similar feature.
Photomicrography gallery: Instagram
Blog: Diatoms Australia
Andor Zyla 5.5 sCMOS | Hamamatsu ORCA-Flash V2 | Nikon Z6 | Olympus Microscope