Calibration Frames Explained
ฝัง
- เผยแพร่เมื่อ 23 มี.ค. 2020
- In this video I explain what calibration frames are, how to take them, and why they're so important for astrophotography. I demonstrate their importance by comparing identical images, one with calibration frames and one without. These images are so important and can really be the difference between an okay image and an amazing image!
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Full explanation on my website under the Tutorials section: www.astroexploring.com
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Watch next! How to stack images in DeepSkyStacker: th-cam.com/video/KPnCGsnyOsw/w-d-xo.html
Thank you. This is by far the best tutorial on the subject I've found. This is the first time I've heard someone actually explain which parts of the process are most important! As a beginner using a DSLR I will now try my first session by skipping dark frames and saving myself a whole lot of time and effort. :-)
Best explanation and illustration of correction frames out there! Thank you!
I'm currently doing my fyp on spectroscopic analysis and this video helps me to understand image reduction process. Thank you so much!
the best explanation about calibration frames i found, superb, cheers mate congrats
You’re too kind! 😃
Superb channel. Just got into AP and didn’t realise how steep the learning curve is. Thanks for all your videos mate really appreciated 👍👍
Thanks Gary! Glad you’re enjoying the content
yep, sold it to me.excellent vid, simple, right amount of detail and most importantly those examples. thanks
That was the BEST video I’ve seen on this topic...clear, concise and easy to follow! Great channel mate and keep up the good work! Waves from north of the border! 👍🏻
Thank you 🙂 glad you liked it!
Very informative and helpful. Thank you
thank you very much for your great tutorial...by watching it, it is the first time I have fully understood these kinde of frames and how to take them. I really excited to get my new skywatcher adventurer and try to follow your tutorials as much as I can. Thanks again for explaining difficult technical things in an easy way.....of course it is not easy...:)
No problem 🙂
Very useful - thanks!
Very very helpful video!! Thanks! 😁
Best explanation ever. Much appreciated
Thanks Perry, glad you liked it!
Very helpful, now i can improve my photos, thank yoou
You’re welcome!
Thank you, very well explained
Well done Nick!
Thanks Bas!
good explanation, however I have argued for years that there is no point in many flat frames or dark flat frames, one + some math is better than 500 of them. One doesn't have to record more than one flat frame and the dark flat frame can be omitted altogether. Just mathematically fit a low frequency 2d surface to the flat frame to get rid of all of the statistical noise, correcting just the low spatial frequency illumination inhomogeinities, including vignetting or sensor related optics. Done. ;-)
Going to desert tonight for some milky way shots. I’m shootings with my wide angle lens but wanted to learn how to take those calibration frames. This video helps!
this is realy fantastic info thank you verry much ) subscribed
Thank you!
excellent presentation
Thank you!
Thanks man
Just about to get started with this hobby and had been mystified about the details of calibration frames. This laid it all out quite nicely! One question, though. I didn't see any substantive difference between how to take flat darks vs. darks. What's the difference? Thanks!
Question: For dark flats, you mentioned the same settings as the flat frames. Now, seeing that I'm using AV mode for those, where the camera sets the shutter speed, am I correct in thinking that when I do dark flat frames I should put the lens cover on and then switch to manual and match the exposure settings the camera set in AV mode for the flats? OR, do i just leave it on AV mode, put the cap and go? I"m thinking this will result in 30'' exposures every time because the camera will not detect any light. Thanks, great video mate!
Hi Nick. Great explanation of calibration frames. Dare I say, I found your explanation better than A'backyard Trev's - definitely sold the idea to me! Time to find an old t-shirt now 👍
Thanks Russell! I’m considering purchasing a light panel to do my flats now but the t-shirt method has saved me well for a couple of years 👍🏻
I do wide field nightscape photography, but I like doing panos, I recently did panos, and even with 50%overlap, there were still stitch lines, I think it's because the lens was vignetted
We’re short tutorial on how to stack light frames dark frames etc
Hey Nick, can flats and bias be used with milky way images? Also when you do the t-shirt bit on AV, I assume you just keep the aperture the same as what it was for the light frames? I do a few cap on darks to put in sequator to help reduce noise during stacking, but not sure if the other techniques can be included let alone what I'm even doing lol
Hi Nick. Comment/Question, seems like there is no difference between a dark and dark-flat unless you do the dark-flats at the exact exposure and make sure you camera is stilll on the optical train. - Cheers Kurt
I'm using a Canon M50 mirrorless camera and a Sigma 16mm prime as this lens I find is best for my sky shooting needs. I don't have a scope attached as I'm not that deep into it yet. If I were just using this setup would you recommend the steps as you've outlined in the vid, bearing in mind that it's a mirrorless camera? I want to improve my shots by this type of method, but only if this method includes my kind of setup.
Very useful video, thanks and I've subscribed. Would any of this be useful for shorter exposures? I am new to the hobby and stacked 150 images of the moon last night, all taken with 600mm lens on my mirrorless canon camera. I added around 30 calibration dark frames just to get some practice but not sure if they made a difference or not. The final image was (in my opinion) pretty good but wondering if these calibration frames even make a difference for short exposure photos.
Hi Paul. For moon photography you don’t really need calibration frames
I just bought a Bahtinov mask and a UV filter for my 70-200 lens. Should I keep the filter on the lens when shooting planets/nebulae, etc or will the UV filter affect the image (reduce certain colors)? PS is there a mask that will fit a Tamron 150-600? I thought an adjustable one (3.5-6.5") would fit, but the person I chatted with at the major photography retailer said there isn't one that will fit my lens. I can't wait to start shooting at anything besides the moon (as long as it's not to cold :))
At 8:56, you said "If you're taking bias frames you don't need to take flat dark frames and vice versa." Please explain why. Thanks.
Great video for us beginners. How many flats do I take? I didn’t hear you mention a number
Thanks! I take 30 flats
Great information for us new guys
Can i ask if you use any sort of filter
should it be left in position for calibration frames?
For taking flats, leaving the filter and keeping the focus the same is very important as you’re isolating dust spots in your imaging train. Not necessary for darks and bias as they’re capturing other types of noise
@@AstroExploring cheers for that Im using a 5nm Astrodon Ha filter tried today but with mixed results will keep on trying thanks for advice
Hi Chris, I think you mentioned in a previous video not to bother with the darks now ?
My name’s Nick 🙂 that’s right, I don’t use darks anymore. I don’t find they help with my DSLR
I'm guessing I don't need dark frames if I'm shooting around 10-20 seconds lights?
Also, do I really need a t-shirt if I'm taking my flats using a tablet screen?
Awesome video! Is it possible to reuse darks? If so for how long?
Darks can’t be reused if using a DSLR. This is due to the temperature of the sensor being variable every time you take an image. It’s actually recommended not to use darks for DSLRs. If you’re using a cooled camera however then I don’t see an issue with reusing them
@@AstroExploring Thanks for the info! I have a DSLR so I probably don’t need them then
For darks and flats are you supposed to keep the light pollution filter in?
Yes you leave the filter in 👍🏻
I’m guilty of not bothering with calibration frames as it has been too confusing to date. That’s great, I think I understand it now. Is there a proper ratio to light/flat frames you recommend (using a DSLR)? Or does it vary according to targets? I’ve tried it at 60/30 with the Iris Nebula and feel it reverses the vignetting way too much. I’m at this exciting hobby almost a year and still very much a newbie!!
I tend to use 50 bias frames and 30 flat frames. That seems to work for me. You want to take a good amount to get a good pattern for your master calibration frame when stacking but there is a point of diminishing returns, i.e. taking 200 flat frames isn’t going to produce better results than taking 50. Hope that helps
@@AstroExploring thanks for your time😊
With flat/dark frames, do they have to be the same exposure as the flat frames? Thank you for all the great information.
Flat darks should be the same exposure as flats yes. They’re essentially the same but with the cap on instead
@@AstroExploring thank you
I don't understand why normal dark frames don't also include the noise that bias frames are designed to eliminate?
Thanks Nick! Much appreciated. Please clarify if you can, which calibration frames reduce dead pixels? I'm guessing it is the bias frames but I'm not sure. What I've been calling dead pixels might be what you are calling "read noise".
Dead pixels can be reduced using dark frames. As they’re pure noise frames, they will subtract this from your lights. However, the better way to remove dead pixels is to dither between frames. I don’t use dark frames anymore when imaging with my DSLR 🙂
Which DSLR do you have?
Canon 650D
When you say "frames", do you mean pictures or videoframes?
Pictures
Can you explain please. You say the Darks need be same exposure length as Lights. Yet if lights will be subs of say for argument 1 minute x 60 of these will be 1 hr. total exposure. But if you're going to save generically 20-40 darks..how can that match the 60 minute Light exposure? I'd imagine you'd want to go 1 for 1. That is, 60 minutes of noise introduction would need balanced by 60 minutes of noise subtraction? I probably understand what you're saying (1 minute subs so take 20-40 one minute Darks, but this makes no sense to me). Embarrassed to say I've been trying at this for over 2 decades and even have a well known astrophotog friend, but I've never picked his brain. Most of the issue is my NYC environment severely limiting my number of attempts and images. Thanks in advance.
Dark frames need to be the same length as a single exposure light frame. So if taking 60 second exposures them for your lights then darks need to be 60 seconds to match, but they don’t need to be the same overall exposure time. So using 20-30 darks is completely fine
AstroExploring I've been anxiously awaiting your response. An astro buff since childhood, I've been actively pursuing this since college and with all imaging tech since film including high end gear for it's time. So sad my brain fogs over on the details. In defense, all my locations prevent views of Polaris and even the hemispheres for proper drift alignment and by the time I setup/takedown in NYC best I get are 30 sec exposures and an hour before my target moves behind obstruction. So all my attempts have been feeble little stabs at it unable to figure out my failures. This should help though. Thank you. Excellent video btw.
AstroExploring One more question please. I'd like to make a library of master calibrations. So if I take say 40 x 1 minute dark frames at say ISO 800, 10 degrees C and stack them (is "stack" correct?) then I would consider it/label it as perhaps MasterDark_60sec_800_10C, even though I took 40 minutes worth?
@@derekec absolutely correct :)
AstroExploring 😌. Oh and I subscribed. Thanks.
I have strange flat frame results, about 30% to the left, is completely black
Timestamp Terry?
Do I need Calibration Frames if I'm taking pictures of the Milky Way with some foreground?
Hi Richmond, yes you should take calibration frames to image the Milky Way with a foreground
That music.... urgh
Haha apologies. The TH-cam audio library isn’t great.