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Final and detailed guide on X5 "lens calibration"

Discussion in 'Zenmuse X5' started by DrMrdalj, Jan 18, 2016.

  1. DrMrdalj

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    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.
     
    #1 DrMrdalj, Jan 18, 2016
    Last edited: Jan 23, 2016
  2. Mark C

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    Thanks Dr for your work on this, clarifies some points for me.
     
  3. DrMrdalj

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    I just have updated this guide with some result of today test - there is a way to use MF Focus Assistant while setting calibrated focus.
    Hope this helps.
     
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  4. zoltanh

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    Thank you for your information. I will re-focus my lens today and let you know how it goes.
     
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  5. zoltanh

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    I sometimes use a dual operator setup on my Inspire 1 PRO and was wondering whether to focus using the Pilot's App or the Camera Operator's app?
     
  6. DrMrdalj

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    You can use both apps, but you should note that they do not "cooperate" seemlesly in real time - "master controller" does not reliably update app on "slave controller" and vice versa... So what you do in one app will not always reflect in other app display (when changing focus point and similar) but it will be visible in realtime in your video feed... Do not get confused when you do see changes in focus in your video feed, but do not see manual focus stripe moving in one app while your change focus in the other - each app refresh displayed parameters on its own, while showing same video feed from Inspire, so you can get in a confusion while apps overlap their controll over camera... Avoid overlaping, but it is quite straightforward to use alternatively both apps, one at the time for controlling the camera in different shots...
     
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  7. Phil-RCGeeks

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    Thanks very much for sharing this information.
    I'll be testing it out tonight!
     
  8. JMac

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    Thanks for the information. My pro came this week and I am hoping go get it setup this weekend.
     
  9. ajohnsonlaird

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    I've sent a Conversation message to you DrMrDalj. But thank you so much for taking the time to create this posting.

    Andy.
     
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  10. ajohnsonlaird

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    I'm glad it turned out to be a quiet day for me, DrMrdalj -- it allowed me to help a fellow Inspire 1 pilot on the other side of the planet!

    Andy.
     
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  11. takean

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    Im having a terrible time getting it to focus. I have tried just about everything I can think of and it still doesn't want to calibrate correctly. :(
     
  12. gruvpix

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    You should make a quick video of you attempting to calibrate the lens so we can see if you are missing a step or doing something wrong. Sounds to me like there might be a problem with your camera but I know it's also easy to miss a step when doing this
     
  13. zoltanh

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    I sometimes use dual operator mode, which controller should i focus my lens in? Pilot or Camera Operator's app?
     
  14. gruvpix

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    I don't think it matters as you are both getting the same feed and have the same control over settings.
     
  15. DrMrdalj

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    As far as I experianced - you should calibrate lens in each GO App on every device you use for focusing. When making any shot you should decide which person will do focusing during that shot - pilot or cameraman or some third crew member... Once decided, that person will use its controller (master contr. if pilot pulls focus, slave contr. if camera operator pulls focus, finger on slave cont. next to cameraman if third person pulls)... It is important that during the shot just one controller is used for focus pulling, any of them but just one for complete shot, as controllers poorly synchronize current focus position from the aircraft - so when you touch the other one (not the controller used up to the moment) it will skip focus to its current position - try it out and you will understand quickly... So, as controllers do not cooperate, any controller (including DJI Follow Focus accessory) can be used, but just one at the time.
     
  16. takean

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    I wont be able to at this moment due to weather. But Here is what I have done. Started off deleting cache, and data files, and then removing the app entirely. Once done, I download the app again to start fresh. Once drone is synced...outside I go. I have a neighbors house that is about 150 meters away...may be slightly less but not by much. I turn the camera into manual mode, and adjust the focus slider to infinite...and its usually blurry...but no big deal...I'm about to calibrate it. So I calibrate the lens...selecting a white corner wall to focus on with a dark green tree backdrop behind the house. Once it is done calibrating, I select infinite..and it appears to focus past the "focus" of the house and blurs up again.

    Now I read once person stating that it took them about 20 trys to get it to hold. I have not had this luck. And If I put it to auto...and click to focus and then shoot...it isn't that clear. It is...but the details aren't that great. Doing manual...well, again, its not calibrating correctly so trying to manually do a streaming 720p image on a smartphone in hopes of getting a 16mp camera still is difficult.

    I do find though, for some strange reason, infinite works fine for video shoots. I get clearer images sometimes with the video that I do with stills. Maybe I'm not doing something correctly...but I'm out of ideas. I love this drone too much to go downgrade to a point and shoot camera. But I don't like to do a lot of post-processing either...especially with the sharpening.

    As a side note..I remember when I first got the drone that it had other features, such as adding in more sharpening to the images before shooting, as well as peak focusing settings. What happened to these? I hear that Apple uses still have them but android users are out of luck?
     
  17. DrMrdalj

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    I did not experiance such calibration inconsistencies. From what you wrote it is obvious that your calibration did not went good - blured image in "infinity focus" shows that lens is focused way past real infinity focus point, while you need it to be at real infinity or slightly closer. Keep in mind that if stock15mm lens at f1.8 is focused at 10m then everything from 5m to infinity should be in focus as well. When focused on 20m then everything from 6m to infinity should be in focus. I strongly reccomend learning about "circle of confusion" and "hyperfocal distance"...
    So, I would reccomend you to calibrate using target which is not so far away, for the stock lens 50m to the target is max, while you can use target at 20m as well... Similar applies even for Olympus 25mm at 1.8 where you can use target at 30m or 40m - just for calibration of Olympus 45mm at 1.8 target should be at 80m or so...
    Natturaly, if you miss some steps in calibration proces results could be confusing. Same is for manual focusing, as you can allways (even when properly calibrated) manualy push focus past infinity without noticing (ther is no any other way to see that happened but from picture itself)...
     
  18. DrMrdalj

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    I use Apple iPad Air2, where Focus Peaking was in General Settings. Now it is gone, I can not find it anymore...
     
  19. Quadpilot

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    Try deleting the app, then loading it again from the App Store.
     
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  20. Hailstone Aerial Films

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    DrMrdalj, I followed all these instructions, step by step. When I got to the "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, and the left thumbwheel to focus precisely on the distant object." It all worked, but I cannot get the subject in focus. It goes from blurry in one direction of the thumb wheel, to not so blurry, but still blurry, when I move the wheel the other way, and then to even more blurry. Never does the enlarged picture get anywhere near sharp. Yes, I have the latest firmware, the Inspire is brand new and the auto focus works fine. The manual focus also works but when the focus assist zooms in on the subject I can't get it to focus. Its just blurry. The app is the most current version as well. There is no software or firmware issues.
    Thanks