Long exposures with Canon SL1

[hefy_jefy]

having just sorted out the polar alignment on my mount I am venturing into some long (20min) exposures with the Canon SL1 (Rebel).  I was wondering about the length of time it takes actually get the image from the camera and download it.  I have not measured it accurately but it seems to take almost as long to transfer the image as it does to make the exposure.  The display shows "busy" for ages - what's actually going on during this period?  Its there a way speed things up?

Is this a function of the camera or my (rather old) PC?

Geoff

 

[hefy_jefy]

OK - yes dug down into the options and came across LENR - it was set to Auto - so its now OFF.  That would explain why it was taking twice a long, although I must say the photo that it produced was not bad!

Now I also found an option called "High ISO speed noise reduction" - that was set to High, options are Low, Standard, High and OFF.  Since I was using ISO 200 for my 20 min exposure I suppose this won't matter too much but might slow things down?

Thanks for this, having now looked back at the manual (duh!), I see that these items are mentioned - I just never realized exactly what the impact would be!

Geoff

[admin]

Download only takes a few seconds, then the image is sent to a background process for a few operations such as reading the exif data... that usually takes about 10 to 20 seconds depending on your computer.

 

Do you have LENR turned on in your camera by any chance?

 

Regards,

[s3igell]

Remember that LENR (Long Exposure Noise Reduction) is Canon's "In-Camera Dark Frame Processing" Feature.  

Immediately after closing the Shutter on the Requested Exposure, the Camera automatically starts a Dark Exposure of the same Duration.  Then it performs an In-Camera Dark Frame Subtraction before writing the result as the Output Image File.

Only then will BYE receive notification of the Download of the Image File, after which BYE can finally start its 10-20 sec Background EXIF Processing.

 

The Canon SDK gives BYE no access to this LENR Setting, so it is the User who needs to ensure this Setting is OFF.