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NPF Rule instead of the 600 Rules

Posted: 07 May 2015, 15:30
by djoubert
Hi,
Good idea to have a rule about slowest shuter speed to avoid star trail.
Nevertheless the 600 rule is a very old rule and I think that it's not the more relevant rule nowdays.
You added a "Real Slowest shutter" which takes into account the pixel size, I dont think it's the most relevant rule
I personnaly use the " simplified NPF rule" which takes into account the aperture, the pixel size, the focal lenght, and possibly the star declinaison
( for this last parameter, actually I set to the worth case : Declinaison = 0 )
have a look to this site ( sorry in french ...)
http://www.sahavre.fr/tutoriels/astroph ... -d-etoiles
Actually this rule applies for a oneshot picture,
In my case when shooting mainly for timelapse I correct the value applying a 1.5 factor
( for video you can manage with a short trail )
For instance , with a full frame and a 14mm focal lengh, pixel size 6,55 ( canon 6D) aperture 2.8
- 600 rule gives 43s / real gives 6,5s/ simplified NPF rule gives 12s / with my 1.5 factor : 18s
I got quite good results until 20s / but never with 42s and Realshutter speed results is too short from my point of view
So I would suggest to replace the 600 rule by such a simplified NPF rule with the ability for the tick if it's for one shot or timelapse
Thank you
Dominique

Re: NPF Rule instead of the 600 Rules

Posted: 20 May 2015, 12:22
by aaronpriest
Agreed!

Re: NPF Rule instead of the 600 Rules

Posted: 20 May 2015, 13:14
by hubaiz
I can add that, but if I calculate from your example I get a different value:
width: 5472
sensor width: 36mm
pixel size: 36 / 5472 = 0,0065 mm = 6,5 micron
aperture: 2.8
focal length: 14mm

shutter = ( 35 * 2,8 + 30 * 6,5 ) / 14 = (98 + 195) / 14 = 20,98

Re: NPF Rule instead of the 600 Rules

Posted: 20 May 2015, 13:57
by aaronpriest
20.98 seconds sounds correct for a 6D and 14mm. I get 17.45 on my 36MP D810 for a 14mm. The Rule 600 calculator in DslrDashboard says 42.86 for the "Rule 600" and 4.80 for the "real slowest shutter" however. Most folks I know use a Rule 500, but I subtract 5 to 10 seconds from that, or use the NPF and round to the nearest interval if I'm not in bulb mode.

Re: NPF Rule instead of the 600 Rules

Posted: 20 May 2015, 14:04
by hubaiz
Will see to add for the next version, I only need to add the aperture field so it is not a problem.

Re: NPF Rule instead of the 600 Rules

Posted: 12 Jun 2015, 19:40
by hubaiz
Next version will have it
npf_shutter.jpg
npf_shutter.jpg (95.84 KiB) Viewed 11508 times

Re: NPF Rule instead of the 600 Rules

Posted: 12 Jun 2015, 22:00
by aaronpriest
Very nice, thanks!!! What is the "real slowest shutter"? How is that calculated?

Re: NPF Rule instead of the 600 Rules

Posted: 13 Jun 2015, 04:54
by hubaiz

Re: NPF Rule instead of the 600 Rules

Posted: 14 Jun 2015, 08:59
by djoubert
Hi,
Thank you very much,
what you propose to implement in the next release meets my expectations.
Any idea about when is scheduled this next release ?
Best Regards
Dominique

Re: NPF Rule instead of the 600 Rules

Posted: 25 Jun 2015, 21:25
by hubaiz
Please check the V0.3 beta, last one is beta4L https://drive.google.com/file/d/0BxMZ8X ... sp=sharing

Will try to make a build for other platforms tomorrow.