Final and detailed guide on X5 "lens calibration"
- Thread starter DrMrdalj
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I just had a brain wave. I don't think the enlarged image is supposed to be "as sharp as a tack" I think its the app using digital zoom, because the Zenmuse doesn't have optical zoom.
So, enlarging the “zoomed” area also enlarges the pixels and reduces the image resolution and the image quality.
I think you just get the zoomed in blurry subject to the not so blurry point, and that will mean the actual zoomed out image is as sharp as a tack. I might be wrong but I think Im right.
I don't know why DrMrdalj didn't mention this because I thought there was something wrong with my camera.
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Yes, you are right - Focus Assist does digital zoom. Please note that almost all video cameras when zoomed above 2x factor (what is HD cutout from 4K readout) have to do digital zoom as well. Therefore every camera (including my favorite Panasonic GH4) when live picture is magnified display digitaly zoomed part of frame. Despite it is zoomed digitaly, due to this magnification you can see more easily what happens to your pixels. Focus Assist zoomed picture, when magnified more then 2x, can not be "tack sharp" while zoomed on any camera, but using this method to judge focus makes your final result "tack sharp" as you can judge minimal degree of defocus more easily. (defocus depends on your lens and aperture as well)...
Regarding X5 and its Focus Assist zooms, after looking at several examples, it is my conclusion that digital video feed which streams from Inspire to your controller gets zoomed (as far as I can see it does not zoom on part of sensor readout, like Panasonic GH4 does it internaly, but it seems that it just makes digital zoom in GO App display). Theferofe, due to compression of video feed from Inspire to controller, this zoomed picture can look more blured then expected even all contrasty pixels are there for you to see...
Hope this clarifies...
Ok thanks DrMrdalj. Now I can calibrate my Zenmuse X5.
In your opinion what is better for video, manual focus to infinity (with what aperture, landscape settings ect) or auto focus.
And does calibrating the camera with manual focus have any effect on auto focus. Like if you stuff up calibration with MF will that effect AF.
In your opinion what is better for video, manual focus to infinity (with what aperture, landscape settings ect) or auto focus.
And does calibrating the camera with manual focus have any effect on auto focus. Like if you stuff up calibration with MF will that effect AF.
To my best knowledge, calibration does not effect auto focus in any way. As far as I learned and confirmed from several sources "calibration" only preprograms infinity button focus point.
Please note that further from some certain focus distance, called "hyperfocus distance", any focusing is irelevant. For wide lenses such distance is prety close, that you need to aditionaly focus just when filming subjects that are less then cca 10m close to camera, on DJI 15mm lens even closer... Fosus is more critical if you use Olympus 25mm and 45mm lenses on close subjects... I sugest that you research "hyperfocus" and "circle of confusuion" if interested in this phenomena...
Theferore, having in mind that I mostly use DJI 15mm lens and film subjects which are at least 5 to 10m away, I mostly rely on preprogramed infinity button. When filming close subjects, 2-4m from the camera, I use autofocus but then I switch to preprogramed (calibrated) infinity once I move away to greater distance...
So, if you calbrated your infinity button well, and if you are not close to your subject, I believe that autofocusing does not make practical sense...
I used f5.7 or something like that. wow, thanks DrMrdalj MF set to infinity after correct calibration is AMAZING. I don't think I'll be going back to AF.
I took note of what he said too but always used AF. It makes sense to use MF now. How did you calibrate your lens?
Just follow DrMrdalj step by step instructions. Get your Inspire in the air first then start the calibration process. Do it exactly as he says and it works. Just note when MF assist starts, (digital zoom on subject) the enlarged picture will be very low quality. Just get it as best as you can. Actually when you hit the sweet spot (with the thumb wheel) the focus assist will end and it will zoom back out to full screen by itself, that means its done.
www.hailstoneaerialfilms.co.nz
To my best knowledge focus assist will not end by itself when you hit the sweet spot - but it will end once you stop dialing that thumb wheel. So, if it happens that you stop dialing your focus in any position, your focus assit will end there on that position and zoom back to full screen, regardless of image sharpness... If you start focusing again by dialing the thumb wheel - focuss assist will engage again.
Thank you for a detailed and informative guide!
It finally made sense and I think I finally made the calibration successfully. Now I have to find sense in the pictureprofiles on this camera. Some say -3 -3 -3, some say that will ruin the image completely and even ADDS sharpness in camera because you will never be able to recover it. This image is taken with the SOFT preset. (-1, 0, 0)
Does it look as sharp as it gets to you?
It finally made sense and I think I finally made the calibration successfully. Now I have to find sense in the pictureprofiles on this camera. Some say -3 -3 -3, some say that will ruin the image completely and even ADDS sharpness in camera because you will never be able to recover it. This image is taken with the SOFT preset. (-1, 0, 0)
Does it look as sharp as it gets to you?
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It's pretty good, very good if no processing has been done, but could go sharper with the correct processing. You can only judge sharpness at the point of focus and only you know where that is.
I would like to clarify the opening statement re Hyperfocal point on a drone.
Hyperfocal point is made by calculating the point where average focus is achieved between two points at a given aperture, unless the lens has these points marked on the lens and you manually set focus by hand to correlate with your chosen aperture to cannot get a true hyperfocal setting, you cannot do it the air, it is not possible unless you are going to refer to a chart coupled with a laser measuring device on the drone.
Having said all of that hyperfocal focussing is for street photography, when taking shots that cannot be focused fast enough, Hyperfocal focussing with auto focus cameras is not needed and is a huge compromise in sharpness, the target is normally soft due to the true point of focus being a foot or so off of the target, further it shows up to be more out of focus due to digitals greater requirement on accurate focusing. Film had a latitude, good digital does not.
The pro way of focusing for still photography is to focus on the critical point of focus and let aperture cover the rest. (there I have given you the secret to sharp shots).
The key point here is that with most drone photography the point of focus is at infinity, you then have to consider how much in front and how much behind do you want in focus i.e. covered by the depth of field, true focus will only be at infinity covering quite a few feet but no more, so the rest is of lower sharpness.
Note that the usual rule is at any given aperture, 1/3 in front to 2/3rds behind for depth of field sharpness.
It is critical with the stock lens to get infinity nailed sharp in setup.
Hyperfocal point is made by calculating the point where average focus is achieved between two points at a given aperture, unless the lens has these points marked on the lens and you manually set focus by hand to correlate with your chosen aperture to cannot get a true hyperfocal setting, you cannot do it the air, it is not possible unless you are going to refer to a chart coupled with a laser measuring device on the drone.
Having said all of that hyperfocal focussing is for street photography, when taking shots that cannot be focused fast enough, Hyperfocal focussing with auto focus cameras is not needed and is a huge compromise in sharpness, the target is normally soft due to the true point of focus being a foot or so off of the target, further it shows up to be more out of focus due to digitals greater requirement on accurate focusing. Film had a latitude, good digital does not.
The pro way of focusing for still photography is to focus on the critical point of focus and let aperture cover the rest. (there I have given you the secret to sharp shots).
The key point here is that with most drone photography the point of focus is at infinity, you then have to consider how much in front and how much behind do you want in focus i.e. covered by the depth of field, true focus will only be at infinity covering quite a few feet but no more, so the rest is of lower sharpness.
Note that the usual rule is at any given aperture, 1/3 in front to 2/3rds behind for depth of field sharpness.
It is critical with the stock lens to get infinity nailed sharp in setup.
Please note that (due sensor size, physical pixel size/density) strict focusing at infinity will give you smaller depth of field (less of foreground in focus) then focusing on some hyperfocal-distant but not "infinitely distant" object. Next to that, please consider that atmospheric phenomena will not allow you to have full sharpness of "inifitely distant" objects with most of your lenses... Therefore DJI sugests calibraring your app's inifity button to an object that is 50m away and that sugestion goes for lenses of all focal distances.
Please note that by "calibration" they just make preset focusing point which you recall by pressing button in the app - therefore you have to "calibrate" each instance of Go app (on all of your devices).
My personal finding for stock 15mm lens was that making infinity button presset at 20m got more of foreground in focus, while distant objects retained their full sharpness as well. For Olympus 12mm lens i was succesefull with less then 15m distance from reference object, while Olympus 45mm was the only lens I preseted at least at 50m... So, yes, there are obvious hyperfocal benefits for wider lenses...
Wide angle lenses always give greater depth of field as do small sensors (MFT) hence f5.6 is equivalent to f11 approx.
Not sure why you want to go to all of this hassle, I calibrate at 50m approx and switch to AF, then tap on the critical focus point and the lens focuses there. You can't get any sharper than that @ f5.6 the lens is at optimum resolution too. simple.
Hyperfocal focussing will not give you critical sharpness as I said previously. it is at best just a best guess, used when you cannot get critical focus.
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I very often fly my camera in single operator setup, while I get pretty close, less than 2m away, to scenery (such as trees, houses, cars, boats...). Beside that I offten shoot in dawn or sunset where F2.0 is neccesity due to poor ISO performance of the camera... As my distance from objects in frame vary greatly and changes in flight I would need to pull focus by constantly acquiring "critical autofocus" so therefore as single operator I set "optimal" fosus as my "infinity button"...
Rest assured that further from certain hyperfocal distance (which is longer when aperture is greater / f-stop smaller) critical focus is of exactly same sharpnes as hyperfocus
so when filming close to objects I manualy aquire critical autofocus at aprox 5m point (and get cca 3m-10m field sharp) and then midflight I recall my "optimal" focus which covers cca 7m to infinity... that is easiest way to pull focus when flying single operator...My exeprience was that with stock 15mm lens focusing at 15m and 50m and 100m just changes foreground depth of field while background sharpness stays almost the same... So I decided to preset 20m... For wide angle Oly 12mm I could set optimal focus even closer at 8m and get everything in focus from 3m to infinity even at f2... Just Oly 45mm mid-tele-lens recquired more than 50m to get calibrate realy sharp infinity
Please note that I strictly write about video shots, while for photo shoting it could be done differently.
So, there is why and how I do, but anyone can have its own preferred procedure...
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I believe that on its narrow end, at 42mm where widest aperture is 5.6, hyperfocal distance is aprox 30m, while at 14mm f3.5 hyperfocal is aprox. 5m away - as this is a zoom lens I would reccomend you to calibrate your infinity button at target that is more than 30m away, to be at the safe side I would opt for aprox 50m...
In common with many Inspire 1 pilots, I have been confused for a long time by the idea of lens calibration. I didn’t have a clue what it meant, why I needed to do it, and how to do it reliably. So I decided to investigate and test – and here is what I found….
Firstly, a “lens calibration” is a misnomer. What you are actually doing is telling the GO app what position the lens should be to have an image in focus when you tap on the Infinity mark on the focusing strip.
Specifically, what you actually want to do is have the lens at its hyperfocal distance – that’s the distance from which everything at that distance to infinity is in focus. Check out Hyperfocal distance - Wikipedia, the free encyclopedia to understand more detail, as well as Circle of confusion - Wikipedia, the free encyclopedia if you’re confused by the circle of confusion
There is no fixed “infinity” focusing position on the X5’s standard lens – and that’s why you need to tell it the GO app what distance is the correct setting for “infinity.” You just tell the app where it should move the lens to have things you want to be in focus.
But you can be sneaky and actually just set the lens to be at the optimal distance for your aerial photography – and not necessarily actually focused at infinity! You can then recall this “optimal focus” distance by tapping on the infinity setting in the app.
Of course, you need to do this lens calibration for all the devices on which you run the GO app.
Just to repeat: Calibrate the GO app on each device and, unless you have a good reason not to, set the lens to the hyperfocal distance – and be sure to do the calibration at the largest aperture the lens has available.
For the DJI 15mm on a Micro 4/3 (MFT) camera, optical theory says that if you set it to its largest aperture of f1.7 and focus to 15 meters (49 feet) then everything from 7 meters (22 feet) to infinity will be in focus (remember my comment about the circle of confusion above).
So here is how to calibrate the GO app for the lens’ hyperfocal distance:
1. Find some fairly large object with contrasting patterns (a building with windows and brick work, for example) which is fairly far away – certainly not less than 50 meters (164 feet) – you’ll still be OK if it’s a bit closer than that.
2. The GO App will force you to calibrate the lens in Video mode with Autofocus (AF) but there is a way to calibrate in Photo mode with manual focus. And this gives you better focus assist and peaking – and that’s the method I’m going to describe, so select Photo Mode before you proceed.
3. Then you need to turn on MF Focus Assistant (it’s under the Menu > Settings (wrench). When you turn on Focus Assistant, you’ll see a zoomed in portion of the frame that makes it easier to see whether the image is properly focused. If you want to use Peaking, set it to 90% (its under General Settings at the top right hard corner of the app.). Under the Menu > Video tab choose Color and select None (do not use D-Log or D-Cinelike as the image is very low contrast and its much harder to see when the image is in focus). Select Style: Landscape (this use +1 sharpening and contrast – which also makes it easier to see when an image is in focus). I’m not really sure whether the Color: None, and Style: Landscape are critical, but they worked best for me.
4. In the Camera parameters (button with sliders, below the record an play buttons) chose Manual Exposure (M) or Aperture Priority (A) and dial in the largest aperture of your lens (the smallest f-number like 1.7 is the largest aperture. Check out Aperture - Wikipedia, the free encyclopedia if you need to understand this in more detail). As I mentioned, using the largest aperture is better for getting the most accurate calibration.
5. Set the camera’s exposure correctly for the scene you are using for calibration. If you prefer to use Manual Exposure, set the shutter speed and ISO rating to get a proper image in the app. If you use Aperture Priority, choose Auto ISO and an appropriate shutter speed, then use EV correction to adjust to the correct exposure.
6. Now choose Menu > Settings (wrench key) > Calibration > Calibrate Now and the Go app will switch to Video Mode and enable Autofocus (AF) mode. This is where you need to tap on the Video/Photo button and switch back to Photo Mode (leaving it in Autofocus).
7. Now look at the image shown on the app and select the distant object you want to use for calibration and tap on it in the image. You should see a green rectangle appear at the point where you tapped – that shows that the lens has focused on the object where you tapped. You can manually correct this focusing point by pressing the C1 button under the remote control and using the left thumbwheel on the remote control – the camera will then switch to Manual Focus mode by itself. Assuming you enabled the Focus Assistant then the app will zoom in on the part of the image where you tapped so you can now use the C1 button (underneath the remote controller on the left hand side as you hold it normally) and the left thumbwheel to focus precisely on the distant object. You may need to go back and forth a bit on the thumbwheel to find the point where the image is “tack sharp” (as photographers say).
When you do this calibration, I recommend that you start by bringing objects into focus that are slightly closer than the distant object you originally tapped on and then move the focus point back out to the original object. Avoid unnecessarily “back focusing” on objects beyond the distant object unless you really need to – remember that the goal is to have the distant object at as the hyperfocal point so that it and everything beyond it in focus. If you back focus on distant mountains, there is a good chance that the distant object you selected might no longer be in focus.
8. Then tap on OK to confirm Calibration and you are done!
9. Be sure to make several test images by tapping on the Infinity mark on the Manual Focus strip in the GO app. Also take some test shots after adjusting the focus point closer than the distant object. Make sure the actual “depth of focus” that you have set is appropriate for what you want to shoot. See Depth of focus - Wikipedia, the free encyclopedia for more details on depth of focus. Make sure that all the objects you need in focus really are in focus!
10. If you like what you see, you’re ready to go fly. Otherwise, simply start over from 1. above.
11. The focus calibration point you set will become the new “infinity” focus setting. You can recall this any time by tapping on the Infinity mark on the focus strip in the GO app. If you use Manual Focus you can either use the focus strip in the app or press the C1 button and the left thumbwheel to focus closer than the “Infinity” setting – you might want to do this for close-ups or to force the background to be out of focus and get some “bokeh” in the image to make the foreground stand out better. See Bokeh - Wikipedia, the free encyclopedia .
For most aerial shots your “Infinity focus” will be all you need.
Important note 1: When using the Manual focus strip, you can tap on the close focus button (the flower) and the lens will focus on its closest possible distance. You can move focus point manually further away using the C1 button and the left thumbwheel.
On the other hand, if you tap on the Infinity mark, the lens will focus on the previously set calibrated distance. You can use the C1 button and the thumbwheel to adjust the focus closer or further from that distance if you want.
But there is a catch: If you use the C1 button and thumbwheel to move beyond the “Infinity distance” you used for calibration and then tap on the Infinity mark on the focus strip the GO app will not refocus the lens back to the Infinity mark distance!! You have to press on the close focus “flower” and then press the Infinity mark again.
Important note 2: In earlier versions of the GO app, the Manual Focus strip had some specific distance marks, and you could read when you reach certain distances such as 5m, 20m and so on. I used version 2.5.1 of the GO app for my testing and it no longer has specific focus marks – so you really don’t know what the actual distances are on the focus strip. Personally, I think this is a shame.
Also, watch out – the close focus flower and the Infinity mark are (for me) at the wrong, and counter-intuitive ends of the focusing strip. The flower is at the top, and the Infinity is at the bottom – they really should be the other way around. The left thumbwheel also goes the wrong way for me. I know beta testers have reported this to DJI, but it is still wrong – my muscle memory and intuition want it them to be transposed.
That said, I really like the concept of the Inspire 1 Pro – it’s a great step forward for professional photography, videography when it comes to an integrated system, and an easy to use camera system. But I have to say that it is very expensive for me and it does not work completely reliably for me. I certainly hope that there are some serious firmware and software updates in the next few months that will improve the reliability.
If anyone at DJI has any comments or suggestions on the above I would be very glad to see them.
This post would not be as precise and clear as it is, if there was no sincere help from Andy Johnson-Laird - I am greatly thankful Andy!
And a final apology if this topic has been covered on another thread – I hope the moderator will move this post where it belongs.
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