Proper "rule" for pinpoint stars with M43

boxerman wrote:

OutsideTheMatrix wrote:

Thanks, it sounds like 5 pixels is my "tipping point" for what I find unacceptable in star trailing. Would you have selected 10 sec rather than 8 sec at 14mm? I'll try again tonight and see what I come up with. For quick judgement of star trails, I'm magnifying the 3" LCD view to 7x first and then 14x.

For my 24 inch print (15 secs, 20 mm lens), I estimated that cutting my star trail down by a factor of 2 would have been fine. That cuts the trail down to 5 pixels! Seems like we're converging on the same tolerance. With a 14 mm lens, 16 mpx sensor, then 5 pixels would be 10 seconds. But, as I say, this is getting down to the psychology of various output sizes and media. On my laptop screen, it seems I don't object to 10 pixels.

I don't exactly recall, but I think 7x turns out to be 100% on my (E-M5) LCD. Sounds like the right magnification to look. 14x couldn't be worse.

13 sec seemed to make close stars blend together so that would be too high, but I could be convinced to go from 8 sec to 10 sec. I'm trying to achieve balance between capturing the most stars (highest possible shutter speed), less trailing (exposures under 13 sec at 14mm) and maintain the most star colors (means keeping the ISO under 3200).

Yes. Lots to juggle. I do hate to go about ISO 1600, though for milky way, you get pushed that far.

My take-away from this for me is 5 pixels seems good for my most optimistic presentation (big print, at close range viewing). This corresponds to 150/f for m4/3, 300/f if you use FF equivalent (i.e., "rule of 500" ... except 300). But, for casual purposes (web or laptop view), I can probably tolerate the full 500 (er, 250/f m4/3 focal length).

Now, camera makers, get the darn noise down...somehow!!

So I did a test run tonight and found that 10 sec is perfectly fine, even with the LCD 14x magnification. 13 sec is questionable; in some frames I could clearly see two separate stars, while in others it looked like a single streak. 15 sec and above at 14mm was definitely not acceptable on the E-PL6, by my eyes anyway.

The formula we acquired earlier to find the shutter speed equivalent to the E-520 was SQRT(1.6) I believe, which comes out to 1.265, so 15/1.265=11.86 sec. So my pinpoint 15 sec exposure at 14mm with the E-520 would be 11.86 sec on the E-PL6, in terms of star trail equivalency anyway. Sounds like the "eye test" of the tipping point being somewhere between 10 sec and 13 sec proved to be correct. How much of a star trail do you get with 13 sec exposure at 14mm? I think I'll keep it to 10 sec just to stay on the right side of tolerance.

I found the same 7x equivalent to my LCD for 100% viewing, but just to be safe, I also view at 14x; it seems like the 10 sec exposure holds well at either magnification.

Is ISO 1600 a bit too low for the Milky Way? Try ISO 2500, it keeps the star colors. ISO 3200 may limit the DR too much and stars go a bit pale. Are you using Auto White Balance?

150/fl is good! Based on the 11.86 sec we acquired earlier for 14mm on a 16mp m4/3 sensor, 150/fl is a really good approximation.

About noise, it seems like our sensors have leveled off since about 2012 or so, noise hasn't gone down much in the newer cameras versus the E-M5/E-PL5 generation.