Fuji XT4 and HDMI capture card

[c_future81]

Hello Everyone.

I just started using Sharpcap pro for a new way of capturing planetary images using my regular Fuji Xt-4 camera.

It was pretty good so far for deepsky images and long exposures using RAW / single photos.

But for planets its just so much better to use the ~6000 frames out of 3 minutes of video footage.
First I tried with internal SD card capturing which "only" delivers 4k in 30fPS with 4:2:0 10 bit color profile in h265 compression at 400mbits datarate at max.
That would still result in a 7.5gigabyte bit mov file after 3mins and 30secs of recording time. which is pretty good I have to say.


But if you attach a HDMI capture card to you notebook with usb 3.2 or thunderbolt and if you have a nvme drive built in, data will be recorded directly in sharpcap at a blistering speed of 1,5 gigabyte per 10 seconds uncompressed in AVI with YUY2 color profile ..but only in FULLHD (which brings me to my question on the bottom)

Opening this video file in autostakkert it shows that I have 16bit color profile active.

Previously I had to process the h265 mov via PIPP into a .ser file and got only 8 bit.
So in theory that should be a big boost in post-processing if i ever get a clear sky again these days

--------------

But my big question to the forum: did anybody else ever tried to capture raw video feed from a DSLR or DLSM via HDMI capture card?
I still have the problem that I can not enable 3840x2160 has the live feed screen will get blank for a second and come back with 1920x1080 saying that a connection to the camera in 3840x2160 can not be established.

is this a usb bandwidth problem maybe? In general this capture card ofc. supports 4k records. currently I just zoom / crop in on the fuji directly. I its a feature for focus control where it digitally zooms in 4 or 8 times.

As jupiter is anyhow not frame filling big, cropping in on the fuji directly and getting FullHD in sharpcap might be anyhow fine as 4k on the camera has a resolution of 8,3 Megapixels. so 4 times cropped would still result into a Fullhd sized output..


has anybody else experience with such a setup / workflow?
for me it would be amazing to do proper Planetary or Moon imaging that way without the need to get a separate camera

thanks!

[admin]

Hi,

that's an interesting approach that I haven't heard of before, so I am afraid I can't comment on the HDMI capture side of things.

I will point out that there is a very good reason that planetary imaging typically uses the camera in 8 bit mode - that's because we use high gain values when planetary imaging to allow short exposures that freeze the seeing. High gain means a noisy image, with pixel values changing dramatically from frame to frame due to the noise (individual frames look speckly). If you capture this sort of image at 10/12/14/16 bit depths, all you are doing is recording the noise in greater detail. It's like if you are measuring the weight of loaves of bread, there is no point in recording the weight down to the last milligram, since the variation from one load to the next will be several grams.

cheers,

Robin

[c_future81]

thanks for your reply!

I meanwhile figured out that it was a problem of the usb 3 - or correctly called: usb 3.1 Gen1 OR previously called usb 3.2
this only features 5GBits of data rate.

Sadly there is no HDMI / USB capture card on the market which uses the newer usb 3.1 gen2 standard which would provide 10 GBits per second bandwidth.
Why It just does not allow connecting to the 4K stream with less frame-rate, i dont know..

BUT

I tried out the AVerMedia Live Gamer BOLT (GC555)
This is the only thunderbolt 3 capture card I could find. Thunderbolt 3 in theory provides 40 GBits and with that one, I could capture 4k resolution in YUY2 with 8 FPS.

but anyhow. sadly also this solution is sadly not perfect.
for Lucky imaging the frame rate is to slow and the AVerMedia card costs around 300€. Cropping into Jupiter or Saturn to only capture those pixels and boots the FPS is also not possible because of no direct sensor access / support like with real astro cameras.

So over all it would be possible, it was a nice try and experiment but after all I will end up using a astro cam I think

But as I'm using around 2000mm focal length which I only can reduce and flatten down to 1780mm or so, I will search for some APS-C sensor again because of the pixel size..

[admin]

Hi,

thanks for reporting back - it's always a challenge when you are attempting things like that which are an 'unusual' approach to imaging, so just posting that you didn't manage to get it to work might be an important resource for someone else in the future who thinks of trying the same thing.

cheers,

Robin

[c_future81]

Hi.

thats why I did
I mean - it does work, but does it pay off?
The idea was to continue using this (in general) great camera for Deepsky (single RAW long time exposure images) and fast sensor readout of Video feed for lucky imaging for Moon and planets through its HDMI port where it delivers uncompressed video Data.

It would work maybe with a faster computer getting 4K footage out with more frames. Or you switch to full HD on the camera and crop into the image to digital zoom into jupiter.
But for the moon where you need the full sensor size, it would not be ideal if you just get 7 FPS.

But yes, it was a nice experiment. Maybe at some other day somebody else has the idea to take footage from a cameras HDMI port

[mathematics28]

Hi.

thats why I did
I mean - it does work, but does it pay off?
The idea was to continue using this (in general) great camera for Deepsky (single RAW long time exposure images) and fast sensor readout of Video feed for lucky imaging for Moon and planets through its HDMI port where it delivers uncompressed video Data.

It would work maybe with a faster computer getting 4K footage out with more frames. Or you switch to full HD on the camera and crop into the image to digital zoom into jupiter.
But for the moon where you need the full sensor size, it would not be ideal if you just get 7 FPS.

But yes, it was a nice experiment. Maybe at some other day somebody else has the idea to take footage from a cameras HDMI port

hi! did you ever figure this out? I had a thought this morning to use my XH-2 and get video out to my Atomos Ninja where I can get 4k60 at 12bit and then maybe use it with Sharpcap somehow or just try to capture the moon/sun without Sharpcap and use the video from the Atomos in autostakkert.

[c_future81]

Hi!

not really. getting uncompressed sensor footage would require the most expensive thunderbolt capture cards but in the end things like ROI for higher frame rates, like for planetary imaging would not be possible.

so i ended up switching to a dedicated APSc astro cam (Touptek) and i'm happy with it.