Tutorial:
Canon 6D / Nikon D800 data transfer

Contents:

1. Introduction, data transfer speed
2. Test with different USB cables
3. Test with INDI DSLR settings
4. To be continued

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

1, Introduction, data transfer speed:

I have used my Canon 6D camera for astrophotography many years. The camera was controlled from a Windows PC in the beginning and later from a Linux server and the Raspberry computer. Whatever system I have used the data transfer time has always been long, 8 to 10 seconds for a 24MB raw image. In that case the camera doesn't store the file on its internal SD memory, transfer the image file direct from an internal camera RAM buffer.

Update:
Nikon D800 data transfer speed added at page 2 and Canon at USB3.

A similar situation is when it stores the images on its internal SD memory. The first 17 raw images is fast because the camera use its internal memory buffer (in multi burst mode). After that it's very slow, about 9 seconds for each image.

I has since many years accepted that I have a very slow camera. Instead of taking photos it spend a long time to transfer files. When doing auto focus with many short exposures it's very time consuming. To get a correct focus the software needs the camera to take at least 15 images. Even when doing plate solving it take a long time.

The camera has a USB 2.0 mini port, its general speed is 480 Mb/sec or 60 MB/sec. A 24 Mbyte image should be downloaded in less than a second. My camera download images with 3 MB/sec.

But now I wonder, does it really has to be that slow ? I found a thread at a forum were they discuss this.

• https://support.usa. canon.com/ kb/ index?page= content&id= ART136995 (How to connect the camera to a computer using a USB cable, Canon EOS 6D)
• https://www.cloudynights.com/ topic/ 598211-canon-6d-slow-write-speed/ (Canon 6D slow write speed, Cloudy Nights)
• https://www.imaging-resource.com/ PRODS/ canon-6d/ canon-6dA6.HTM (Canon 6D Performance, Imaging Resource)
• https://tethertools.com/blog/canon-eos-6d-tethering-cable/ (Canon EOS 6D Tethering Cable, Tehter Tools)

It was about how long time it take to down load the image on the cameras SD memory. Some says it took at least 3 seconds but there were also people that says it only takes 1 second. Reading through and it depends on the SD card's write speed. The write speed is very slow compare to the read speed. In my case the SD card has a read speed of 45 MB/s, but the write speed is only 10MB/s, a 24MB file will then take almost 3 seconds.

For me it doesn't matter because I normally doesn't store the images on the cameras SD memory, if I want I only have to buy a faster SD card. But after reading this I thought, maybe there is a similar problem with the transfer speed. I asked the question on the Cloudy Nights forum. Some says it can transfer the files from the camera in just three second, much faster than my 9 seconds. In this case it doesn't have anything to do with the SD card, but the USB cables can be a problem.

My todays astrophotography rig, the Canon lens is today replaced by a Pentax 645 300 mm f4 ED lens. Controlled by a Raspberry computer.