Continuous Autofocus for Canon


#1

I originally emailed this, but the autoresponse indicated that the correct way to submit a feature request was through the forum. Apologies if this has already been posted, but perhaps with more expressed interest…

My interest in Astro is widefield imaging. I use modified canon cameras and conventional camera lenses. I shoot with 300f2.8isII, 70-200, 24-70… all at f2.8. This is a curse AND a blessing. I am able to collect a lot of data in relatively short amount of time but the focus is not very forgiving at f2.8. Despite putting my gear out hours before shooting to acclimate to ambient temp I still get focus drift throughout a session. At first I refocus every 20 min, then this frequency drops and after a couple hours I rarely need to refocus. I’m currently using BYEOS which itself is feature rich and very easy to implement, and it offers manual focus adjustment in software. Seeing that I am using lenses and not 10:1 focusers this feature is essential to dial in the focus.

One thing about SGP that catches my attention is that you implement a very capable focusing algorithm that works with autofocusers to keep everything in focus despite the will of temperature changes to pull images out of focus. What a dream this would be for Canon AF lenses! Is this a feature that you are hoping to implement in a future version of SGP? If so, I do have another suggestion on how to implement this. I’m not sure if your current algorithm assesses an entire image for focus or if you can select specific stars or regions of the frame, but for me the latter would be essential. As you know, with lenses our fields are not flat, and interestingly, I am finding that with my f2.8 lenses I need to achieve focus at specific spots within the image circle to achieve a balance focus. (with my 300mm I need to focus in between the center and the left edge of the frame). When I do this, I get equal distortion across the entire frame. If I focus at the center I have OOF stars on the left and tack sharp to the right. I originally thought my lens was out of collimation but after rigorous testing with Canon CPS I found this was not the case. All my f2.8 lenses behave like this. Whether it is the lens or the sensor I do not know, but each lens has it’s sweet focus spot. Anyway, if you were to implement a continuous AF feature for Canon Lenses, I think it would
need to allow the user to manually select the sweet spot for critical focus.

Anyway, love the feature set you offer and thank you for your time. If you do implement a continuous AF that works with Canon and the AF lenses this single feature would be a HUGE selling point for your
software and would really pull many of us who currently use other methods to dive in with both feet.


#2

If you couple an electronic focuser to your Canon lens with a belt, SGP can make AF for you…
There are several examples of such setups on the web, for instance here : http://www.astronome.fr/produit-moteurs-de-mise-au-point-robofocus-653.html (see “kit Mandel”)


#3

Pulsar, I think he’s talk about using the lens motors to focus the camera. BYEOS and several other camera programs (qDSLRDashboard being one of them) can do it as well. It’s included in the SDKs for both Nikon and Canon.

I too would like to see this feature added.


#4

This is exactly what I’m hoping for. I use a variety of canon AF lenses and don’t want to have a “rigged” solution. It would be great to be able to utilize the lens motors to perform this task.


#5

Closing as duplicates:


#6

www.mainsequencesoftware.com