Many thanks for this. A brilliant explanation of a difficult subject. I only started astro-photography a few weeks ago and everyone told me to use the 500 rule but I was disappointed by the results and thought it was me, my technique and was ready to give up. I already have PhotoPills but didn't realise the solution was already there in my hands. I am looking forward to the next opportunities to give this a go.
Enjoy your videos immensely enjoy involved in photography for 50 years although I’m completely new to astrophotography. I shoot an APSC DSLR so what’s the focal length of the lens for the purpose of this equation using a 300 mm lens? Is it the focal length on the lens, 300 mm or using the APSC crop factor (Nikon camera) 450 mm. Thank you.
As usual, an interesting and informative video and you do speak fairly slowly and have really good diction that helps make the subject understandable. But a couple comments/suggestions: You should adjust the Rule of 500 or any similar rule to account for the "crop factor" for cameras with a smaller sensor. Many Canon and Nikon cameras are APS-C, which have a crop factor of 1.6 (1.5 for Nikon). That means your "Nifty 50" lens acts like an 80 mm lens, and thus the Rule of 500 should produce a max. exposure of 6.25 sec. rather than 10 sec. Also, as you mentioned, you can get a more conservative value from the Rule of 400, which produces 8 sec. for a full-frame or 5 sec. for an APS-C. Then there is the 4-crop rule: t = 100*(4-crop)/f or 100*(4-1.6)/50 = 4.8 sec. This is less unconservative than the 500 or 400 rules but more conservative than the simplified NPF. Of course, none of these simple rules account for the distance from the celestial equator as you mention and which Frédéric Michaud 's NPF or MFN rule incorporates. I wrote to Frédéric last year and he sent a link for an updated page that at the time (since changed) started with the 4-crop rule. Finally, the crop factor is even more important for smaller sensors. My Sony RX-10 has a crop factor of 2.73 while an iPhone 6 or 6s has a factor of 7.21. Of course, with proper pixel pitch data, the NPF rule will account for a small sensor.
Hi Nico, first of all congratulations to your video. You are very proficient in the subject and try to simplify things to be understood for all. Your explanation has a fair rhythm and it very instructive as well. Hats off.👏👏👏
Great video. Loved that you showed zoom results of your shots using different exposure times. I started using 500 rule and then switched to 400 rule but never got super sharp stars. Can't wait to try this rule to take future shots.
Very interesting video, Nico. The 500 Rule was a bust the first 3 or 4 times I tried to use it. I ended up experimenting with different times until the results were acceptable, but I couldn't predict a successful outcome. It appears NPF does that. Now, if only I could catch a clear night to test...
Thank John! I definitely recommend experimenting for yourself. I've been wanting to experiment with different rules, lenses, and cameras for awhile, and I thought I might as well make it into a video. Clear skies!!
Dude. This is soooo informative. I have had Photopills for years and never used the declination field in the NPF. Also, I had no clue sensor resolution affected star trailing, but it makes so much sense. Now I REALLY want the Sony A7S or A7SIII. Excellent video sir 👏👏👏👏
Hey, great video. I've subscribed. So I am a new to photography and I am going to attempt the capture the comet tonight. I have a Canon T2i and a 18-55mm f/3.6-5.5 lens. Best I have for now. Can I use the photo stacking technique in a attempt to get a better shot of the comet?
Yes! The Comet does move slightly faster than the stars, but over a short time span (20 minutes) it is fine to just register using the stars. If stacking over an hour of data, it's better to use deep sky stackers comet alignment mode
Great video, this makes a lot of sense and I always wondered what the NPF Rule was in the Photopills app. Now I know more. I will certainly take this into account when I go out to shoot. :)
this is an over simplification of the rule, I believe 500 /mm = is based on 35mm sensor size, so this needs to be factored in so for canon Full frame that's correct but it should be adjusted for APSC and APSH size Sensors so the corrected formula should be 500/ (mm * Crop Factor) so for an a canon APSC size the formula would be 500/(50*1.5) = 6.7 sec vs 10 sec with out the crop factor thats a big difference. I have found some texts that say not all 35mm "equivalent" are the same as Film 35mm and they should be factored to 1.1 or 1.2.
Hi Chris, In preparing for this video, I did come across a number of articles that suggested what you are saying here. I considered covering it, but thought it was too big a distraction. I don't think that with the cameras available today multiplying 500 by the crop factor make any sense if your goal is the longest exposure with round stars. What actually matters is image scale and to calculate image scale, you don't need to know the dimensions of the sensor, just the size (pitch) of the pixels. It's true that in the early days crop-sensor cameras almost always had smaller pixels than full frame so the concept of multiplying by a crop factor had some merit. Today, with very high resolution full frame sensors that boast 4 micron pixels, the crop factor addition to the rule is a distraction more than a help. Hopefully this makes sense. I tried to cover it a little bit in the video, but not sure if it was my best explanation ever: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RCkhpzM0e7o.html Cheers, Nico
An outstanding video, Nico. Thank you so much. Since retiring, I am revitalizing my adolescent-years’ interest in nature photography with all of the new technology. I’m beginning to get in to astrophotography as well. I recently acquired Lightroom/Photoshop, so I am very interested in watching your photo stacking video. Interesting to know that you are a librarian and are well positioned to share your knowledge and learned skills with all of us. You’re videos are always well thought out and presented in a very clear and concise manner. I thoroughly enjoy your channel. Clear Skies to you!
I'm just thankful for all the great information you give out for free on here. I think most people missed the fact that you used to have to pay a lot of money to get this kind of teaching. And I would definitely say the information you give is worth paying for. That being said man I wanted to let you know I just bought hey starshoot by Orion a small equatorial camera mount sort of like the ioptron. So I'm finally going to be able to take exposures longer than 30 seconds. Which is what I was limited to with my ALT Azimuth Mount do to field rotation. So I'll definitely be re-watching all your videos so I can process that data correctly.
Hey. Could you do a video on astrophotography with a film camera? I have a K1000, and I would like to see what could be done with that. I would try it myself, but I have a family issues that is demanding my time. That's also why my astrophotography setup is gonna be a star tracker and, at most, a small refractor. But likely just lens based. But I have a film camera that is 35mm and it takes great day pictures and I think it would be interesting to see how it works for astro pictures. Thanks in advance!
I used the rule of 500 when I started and discovered that it is too high. I quickly switched to 400. If you need the extra time, just get a star tracker for crying out loud. 😄
Thanks Giuseppe! I am currently trying to build a spectrophotometer to test astronomy filters. So hopefully there will be more of the scientific approach coming soon! Cheers, Nico
@@NebulaPhotos great, the reason why i am attracted by this kind of approach is because i am graduated in astronomy here in Italy! Good luck for this project! Keep all us updated!see u soon Nico!
For folk who don't have a remote set your exposure more than you need by say five seconds you can cover the lens hit the button..but don't bump it with the cover..and wait a few seconds remove it for your determined exposure time then put it back in front before your timer closes the shutter. Great video.
@@NebulaPhotos Why not, i consider this as a true master class channel, and this is the reason why i am here. I hope your videao with stacking for single exposures will be out soon. I want to learn how to preform beter quality pics, cause i really like astronomy.
You are right, the 500 rule comes from history. If you use a film (24mm by 36mm) and you accept a strartrail of 300µm in your 8" * 12" (200mm * 300mm) print, the startrail on your film is about 36µm long. So with this data from history you can calculate with a pixelsize of 36µm. If you calculate 13,7 * 36µm / 50mm = 9,864sec. The 500 rule said 500 / 50mm = 10sec. And 9,864 is nearly the same like 10sec.
I went out last night and tested NPF with my circa 2006 Nikon D40 and a prime 50 lens on Ursa Minor (Lat 40, ~45 above horizon). The tool says 32.8 second exposures, which is three times the 500 Rule! I was expecting shorter exposures, not longer ones. Shockingly, I was able to get dots (or as close to dots as my non-Live View-enabled camera would allow. Amazing! I am sold on NPF, and will more than likely be buying Photopills so that I can have access to NPF without having to drag my laptop along.
Yes, taking declination in to consideration will make a huge difference when shooting the the North Celestial Pole (Ursa Minor) or the South Celestial Pole (in the Southern Hemispher). Glad the rule was working. Clear skies, Nico
Sure! The NPF rule would be more precise, but a rule of 200 or 300 would work in a pinch and be a better starting place for round stars than 400 or 500
I feel that the complex NPF is something that we should rely on when using ultra wide lens. I have a Tokina 11-16mm lens and find that the stars on the edges are very "streaky".
Yes, I like how on the website he shows the NPF rule across different sections of the sensor. It is quite possible with a wide lens to have streaking on one side due to declination difference. I still haven't found an ultra-wide that doesn't have mis-shapen stars at the edge (due to optical design) even with tracking. I think it's very hard to get an ultra-wide lens to do that.
This 500÷f mm rule... Does it apply on 1.5x (Nikon/S0NY) ~ 1.6x (Canon) APC Cameras? Or is this a carry over from the bad old 35mm Film days? Where such a rule could only continue to make sence on the more expensive Full-frame Bodies?
It only makes sense on even the full-frame bodies if you are taking a single exposure, not stacking. With stacking the higher precision of digital bodies means we need a different rule as the stars will not be round with the 500 rule. I like NPF as shown in this video, but some will try to get away with a 400 or 300 rule. I argue (see video for more details) that those don't make sense anymore because they ignore pixel pitch. Today you can have full frame cameras with huge pixels (e.g. Sony A7S series) or small pixels. It's not sensor size that is the determining factor, it's focal length + pixel pitch, also called pixel scale or plate scale.
Your stating you won the OPT was not really valid. With that photo who is looking at the stars. No one. I was thinking pixel density would play a role. Just like a film would be dependent upon Crystal size, i.e. ASA. High ASA for astrophotography.
I think we are in agreement. 👍 The point I was trying to make was for Aurora and other nightscapes having streaked stars doesn't distract from the beauty of the image. In fact, the average person would never notice!
Too early to say. Most of the specs that matter to astrophotography have not been released. Some things that are important for astrophotography, we won't know till someone has it and tries doing ap with it. I am definitely interested though. If it comes in at around 3k, I would be tempted.
Depends on goals/ preferences and whether or not you will stack. Generally with that lens, I'd go f/4, 6 s for the cleaner stars, esp. if you plan to stack.
the pixel pitch speech was unnecessarily confusing. intuitively, its obvious higher resolution cameras will show more trail because it's showing more detail.
I've heard a lot of people say you need to apply crop factor to rule of 500, thinking that the size of the sensor rather than the size of the pixel pitch is the important factor, so I don't think its actually intuitive, but sorry my explanation was overly complex
NPF more conservative? Not really. If you use a longer focal length and look close to the North Star in the northern hemisphere, or to the Southern Cross in the southern hemisphere then NPF expo time may well be much longer than the 500 rule allowing the use of a lower ISO. So if you correctly use it, the NPF rule avoids star trails closer to the celestial equator and less noisy shots close to the celestial poles
True, it takes in to account declination (which I mention in the video), and close to either the NCP or SCP this can make a big difference. However for about 90%+ of the sky, the NPF rule will be a lot more conservative than the 500 rule, meaning shorter exposures and rounder stars.
As a novice, I did the 500 rule. Then I realized it is off. Even going wide angle I could see the slight trailing even leaving a decent picture. I just started removing 1-2 seconds and issue resolved. Found the 400 rule but went back to 500 rule subtracting 1-2 seconds which is fairly close to 400 but 500 is more comfortable for me for some reason.
you cleared my doubts , i heared about it before , but i have to use more and more iso(npf rule exp-8 sec )for my 17mm ,f/2.8 lens , 500 rule (30sec)- i can use lower iso , what should i do ?what do you recommend ?
Try these formula that I came up with. 360/fmm=ts for little egg stars with exposure times close to the simplified MFN formula. 360/fmm/2.2=ts for better stars with exposure times close to the full NPF formula. Regards, Jas. vk4fjgs Rockhampton Queensland Australia
The one thing that the 500 rule doesn’t take into account is the crop factor which will have different results from full frame sensor to crop sensor if you just go by the 500 rule without taking the crop factor into account
Doe's the NPF rule calculator take in to consideration if you are using a crop sensor camera (I think it does) or must I first calculate the lens size before entering that data in? Anyone else seeing may answer it would help this old man out
@@NebulaPhotos The maximum angular resolution in radians is about 1.2×wavelength/diameter of effective aperture. If you multiply this number with your focal length you get what I called the 'Heisenberg uncertainty'. If your pixels are significantly smaller than this the pixel size does not really matter any more. For most lenses effective aperture is equivalent to front element diameter. Of cause all of these effects can onely be observed if the atmospheric conditions are good enough. The phenomenon is caused by the wave like nature of quantum objects. If you would like to lern more about this you can Google 'single slit diffraction'.
Ummmm, no. That would just be the Rule of 166, which in many cases would be unnecessarily conservative since it doesn't take in to account pixel pitch or declination. Like I said NPF is a better rule if you plan to stack. If you don't plan to stack and are just doing single exposure milky way, use whatever gives you the results you are looking for be it rule of 509, 400, or 166. :)
Have you ever heard of exposure bracketing. Just take a shot at 3,4,5,6,7,8,9 and 10 seconds or a 55 second shot and one of them will be right. There is your rule to find the right exposure. Post processing will give you the best answer. We all know that 3 seconds will be better than 10 seconds. You just won't get as much light. With exposure bracketing, you can then make the proper trade off between light and star tracking for your picture.
It is very hard to judge star trailing when out in the field on a tiny dslr screen even zoomed all the way in. So it wouldn't matter that I can take a bunch of different test lengths with bracketing. The formula is much easier. This video is just long because I wanted to explain the formula and test it against other exposure rules.
@@NebulaPhotos Yes, I agree that the formula works to give you a ballpark starting point for your exposure. My point is that when it doubt, just exposure bracket your work. If the formula says 10 seconds then take an 8 second and 6 second exposure too. When you get back home to a larger monitor then make your best choice of your pictures for future work. My comment was to point out that an additional 14 seconds of time is meaningless in the total time taking pictures to get the best one. I also understand that if you are going to take 1,024 pictures then 14,336 seconds will make a huge difference and you better make the right guess the first time. That is when you need to experiment with your setup first to determine the best exposure time before hand. There really is no need to get too complex in the exact formula for exposure time. There is a big difference between theoretical and practical procedures. Sometimes close enough is good enough.
@@richardcommins4926 I agree there is often a difference between theoretical and practical. That was my motivation for making this video to see if the NPF formula holds up practically. with many different focal lengths. It did. I could see the bracket argument for single exposure milky way, but I think it would be overly complicated for a stacked deep sky workflow as you would end up spending more time sorting and deleting files you won't end up using. The formula is a bit complex, but it's built in to PhotoPills app, websites, etc. to make it easy.
Yeah, as you said in the summary it depends on what one wants/accepts. Also, with a shorter exposure we have to bump up the ISO hence more noise :( It's all about the balance.
For most camera models I've seen ISO 800 is a good compromise value. Canon models typically have way too much read noise at low ISO values 100, 200, even 400. So often ISO800 or 1600 is where the read noise starts leveling off to 2-3 electrons. Sony sensors (most modern Nikon bodies use Sony sensors too) are more ISO invariant meaning low read noise even at low ISO in which case it may be advantageous to use lower than ISO 800 for more dynamic range and possibly better star color, although it is rare to fully saturate the stars without a tracker
Hi, I have been told the 500 rule is only valid with full frame camera. For APS-C it is 400 or 350 dived by focal lens. But I didn’t know this new rule... Thank’s a lot. JM (from Nice in France).
Hi Jean-Marc, I think that makes some sense as APS-C sensors typically have a finer pixel pitch. Although as you can see in my testing in the video both the Rule of 500 and 400 resulted in trailing with my full frame DSLR. Clear skies, Nico
Claro q he aprendido bastante y quiero seguir aprendien , gran trabajo muy agradecido por el tiempo y la dedicacion Nebula Photos , saludos desde Lima Peru.
de ser asi tendria q tomar en cuenta el factor de recorte por ser aps-c ? y de ser asi estaria bien comprar el 50mm 1.8 u otro mas apropiado , te agradezco de antemano las respuestas.
the rule was originally established based on a set magnification for photographic film i’m guessing ... so it’s based on a set print size and viewing distance i assume
But if you do that with a digital sensor it doesn’t “work”. I can still see the stars are streamed on an 8x10 print. More noticeable as you increase focal length
depends on a lot of things - also not suitable for analogue when the film is higher resolution than 35mm etc etc ... the 'standard' was also likely meant to be compatible for halftone plates in book publishing
@@antigen4 Do you know if the rule was published anywhere pre-internet or was it just word-of-mouth? As I said in the video, I looked through many books (pre-1990) on astrophotography, and couldn't find it mentioned in any of them. Cheers, Nico
i really don't know sorry - i may have come across it a very long time ago but i'm unsure. There are equivalent 'rules' however for offset and digital printing - suggesting using 200 pixels per inch on printed materials to seem 'reasonably' sharp. However i'm more of a fan of images that can be critically sharp well beyond casual viewing distance - like aerial reconnaissance photos or plates from an astronomical schmidt camera etc etc (12 x 12 inches but contain enough detail to probably blow up to 4x4 feet or so)
I've found two android apps which seem to give roughly the same results as the photopills and the website of the NPF rule, they are "pin point stars" and "shutter speed calculator", and they are for free. In fact the last one lets you choose between the 500 rule and the NPF so you would be able to compare.
i have been saying this for 3 years now and people kept disagreeing with me i have been doing the 300 rule... cameras are soo much more advanced great job for bringing this up
Thanks for your comment Ben! How has the rule of 300 been working for you. From my quick calculations, it seems a rule of 300 would be closest to the simplified NPF rule. The complex NPF rule is typically more conservative than that. The exception being close to the celestial poles.
