Focus information in meta data

[guybunce2016]

Focus has always been a problem I have had since I got my new Canon 6D and Sigma 20mm f1.4.

 

Last night, I managed to get the best focus I have had yet.  I did it manually using live mode.  I was wondering if the exact focus I used was recorded in the meta data of the photos I took last night.  My thinking is that if I know where to look for this 'number' I can use it to get the same focus again in the future.

 

Thanks for your help in advance.

[astroman133]

You can look at the metadata that the camera, and optionally BYE, puts into each image. In either Imaging or Preview modes click on the button in the Image Center with the Rubik's Cube icon to see the metadata of the displayed image.

 

That said, I am not sure what value would apply, or how consistent it would be between sessions.

 

One of the issues with focusing through lenses, especially short focal length lenses, is that the stars are not usually bright enough or large enough to be visible in LiveView.

 

However, while in Frame & Focus mode you can take short Snap exposures (say 5-10 seconds). When the image is displayed you can move the Zoom box around the brightest star. This should give you a FWHM or HFD value. Then adjust the focus and take another short exposure and repeat until you are satisfied. Using this method is not as convenient as LiveView, but it is very similar to what is required when using an astro-CCD camera.

[admin]

 My thinking is that if I know where to look for this 'number' I can use it to get the same focus again in the future.

 

That would be useless actually.

 

You only have to get the lowest FWHM number possible at the time of focus.  The number will change due to seeing on a given night so looking for the same night after night is not appropriate.

 

Regards.