Garnett, this should be required viewing for everyone who is thinking about doing DSLR astrophotography. The histogram is one of the least understood tools to the beginner. You're did a fantastic job explaining it at the fundamental / basic level!
Thank you and that means a lot coming from a guy as technically savvy as yourself. I’ll admit it took me a while to figure out the best way I could convey the message.
Echoing what Allen Mitchell said, I just learned more in 8 minutes than I have in six months of fumbling around watching other Astrophotographers on RU-vid capture and process their data. I actually had one of my photos open and was looking at the histogram during the video, thinking "but what about this, I haven't seen an example of this...OMG there it is, he just drew it now I know what this means!" Thank you!
Thank you. Your feedback means a lot to me. I have an unorthodox approach but I value information way more than entertainment. I absolutely love this community and I do my best to fill in the gaps where needed. Thank you for watching and taking the time to comment. I’m considering making a video about “over processing”. A bad trend is being set lately. Most astrophotographers obviously weren’t professional photographers before they started. A video about an image that takes thirty adjustment layers to fix is far less useful than a short video about measuring the quality of good data acquisition. Happy new year. Clear skies.
I'm fairly new to astronomy but just started learning astrophotography, and regular photography. This explains so much in a simple way, most tutorials just show histograms and don't actually explain how they work. Thank you.
This should be mandatory of all astrophotographers to learn and understand. This is by far the most important and relevant information I learned on astro-processing.
The video as a whole was great, but the section on stretching, especially on when it's been stretched too far, were extremely helpful. Thank you very much for creating this.
THANK YOU for this. This just made everything make sense to me now. Post processing is for me the hardest part of astrophotography and you have just help me greatly. 🙏🏼🙏🏼
Thank you. I appreciate you. I have unorthodox methods but they seem effective. I’ll be active soon. In the middle of gear acquisition during this shipping delay situation
Thank you for watching. My goal was exactly that. Demystify the topic and waste zero time. It’s easy to turn histogram into a 500 page book. I didn’t enjoy reading those either. Clear skies.
Great info! I'm learning and was doing multiple exposure lengths and ISO setting as i was experimenting and stacked them all together and the result for 53m is from what other say it's very impressive with a lot of signal and said wish they could do them that good so early in the hobby and I put it down to the variety of data sets as most just do say 5m exposures at low ISO/gain and there is no extra data from other ISO or exposure types they may fill in some gaps. It was a fluke through experimentation but clearly it works and your video just reinforced that for me so thank you! I've shared this to multiple astrophotography pages too cheers.
Thank you so much for the feedback. I only publish things I try myself. I do a lot of testing. Nothing against the community but there is a definite trend going around where people just pass off what they believe to be true. I think the same is true about overcomplicating things. This hobby has way too many pitfalls to be stuck philosophizing over complex formulas. Ultimately it’s passion and the experience. Both of those things are hugely different for each and every one of us. Clear skies.
This is superb tutorial. I learnt so much. Maybe you can bring examples to trach us more, different types eg. solar images in white light, Ha fillters, light pollution filters and effect on histogram. Milky way with landscape. Isolated star scapes eg milky way at zenith, constellations without horizon or other artifacts and how to optimise the photo via histogram application to adjust framing and ISO, aperture and exposure duration.
Thank you for this...I am just starting out, and I am capturing Orion, learning how to adjust is difficult. This explains some of the mistakes I am making.
Good video, do not be afraid to narrate your videos, this will bring/hold more viewers, even if you dont speak good english. But i have an issue with statement "stacking does not reduce noise" and then contradicting yourself right away by explaining with "rather increases signal to noise ratio" - that means, it reduces noise and increases signal - so stacking does reduce noise :) Maybe what you thought was, that it doesnt generate new signal/information. But it definitely reduces noise.
That’s arguable. Noise reduction by literal definition that is to say. I should elaborate further but certainly the point is clarity in integration time. I suppose for simplicity’s sake it can be perceived either way. It’s essentially still there you just have a higher ratio of good signal to bad signal. This is always a complicated topic and you’re sharp to see it the way you do. I’m hoping to illustrate it as the ratio of good to bad signal. Too many people think stacking software has a magic “erase noise” feature and that’s simply not what’s happening in an average, median, etc. A good example is the noise reduction tool in Lightroom. It’s attempt at smoothing an image also shows deterioration of image quality especially when pushed too high. It’s very destructive just much less so for well lit shots. Clear skies.
Hi, I have a question about the histograms I get. I take photos through my Newton 10/F4 and DSLR Canon 1100D. I am using Maxim DL to acquire the shots - usually 120s subs under a heavy light-polluted sky. Right after acquisition, the histogram of my photos (any photo) looks like it has two "sky peaks" separated by a sharp deep "rift". The value of the histogram in these bins between those two sky peaks is zero. The two separated peaks stay even after calibration, and color conversion. Is this something normal, or do I do something wrong?
Bimodal histograms are common in gloomy conditions. The approach I’d take is to try and center both peaks. There’s a limited amount of mid tones it seems. If I was you I would be VERY interested in seeing what kind of histogram I could produce in better conditions. What is the inverse such as a daytime shot with the same equipment? Likely it’s just representative of your bad skies. Lots of highlight and shadow data with very little mid tones due to a washed out sky. Consider a light pollution suppression filter. Get a cheap one just to see if it corrects the problem. I hope you figure it out. It sounds like an editing nightmare. Clear skies.
@@GarnettLeary Thank you for your answer. I don't think it's really "bimodal". To illustrate what I mean I made a compilation of histograms from typical uncalibrated frames (light, dark, bias, flat) www.dropbox.com/s/er50b799yxxe2fa/light_dark_bias_flat_histogram.jpg?dl=0 The strange histogram stays even after calibration, color conversion and 2x2 binning. I am using a LP filter - IDAS Nebula Filter LPS-D1- but it makes no difference when it comes to the bizarre look of the histograms.
I come from the days of film photography, and your part on ISO is totally opposite. You always shot with the lowest ISO you could get away with for a particular job. When digital cameras were introduced, I always wondered how they got ISO ratings so astronomically (pun intended) high.
Yeah it seems a bit backwards at first glance. My first film camera was a Yashica Lynx 4. I couldn’t agree more as anyone familiar with ASA would. The key to it is available light. Photons from distant galaxies and nebula are heavily influenced by distance and atmosphere. Additionally you contend with the Bayer Matrix, although good at determining neutral grey, is an enemy of photon collection. If anyone uses what would make sense as a “correct” exposure following conventional ideals they’ll quickly find their histogram piled up on the left. You’ll have a bunch of data that’s unusable. For years one could recommend ISO 800-1600 as a great starting point. That amount of amplification could draw out faint fuzzies. These days sensors are so amazing it’s not uncommon to see Milky Way shots composed of ISO 6400 singles. Occasionally you use conventional thinking. The Moon is a good example. The Great Orion Nebula, although extremely bright, must be shot with varying exposure settings due to its high dynamic range. Objects such as these can catch folks with their pants down that have no understanding of photography basics. I find it amazing that all astrophotography was once done on film. A guider was an actual person, sometimes riding inside a telescope. When I consider my Canon 6D I often shoot around 4000-6400. The noise is mitigated through stacking and calibration frames. Digital media has opened the doors to everyone. It would be interesting to see someone taking film on these days. Happy new year. Clear skies.
@@GarnettLeary Thanks for the reply. I'm just getting started in astrophotography. In fact I don't even have my telescope and mount yet. So, until it arrives, I'm doing lots of studying and found your video and reply enlightening. Thanks again.
I thought pausing and writing it down would be more effective than interpreting my deep south, clear eyes scientist, monotonous dialog. Sorry for the inconvenience. Lol @ self.
