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Author Topic: 8mp iPhone results - Promising start but....  (Read 2655 times)

10kclockman

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8mp iPhone results - Promising start but....
« on: July 28, 2016, 09:56:13 AM »
Hi, I have built a turntable rig to scan hands and am working with an orthopedic surgeon. The results are getting better and better.  I have attached a screen shot for information.  I want to use iPhones as I want to create a usable system that works with easily available cameras.  Please look at the image and help me make it better. BTW, I am using a mask to remove the background which is very effective.  I am using a stage prop hand at the moment and am building a rig to keep a human hand stationary.  I suppose my real question is, is this as good as it gets or could I do more to get greater resolution.  To be honest, we think that this is almost there.  Finally, the model comes out tiny, we have to scale it in the 3d printing program to get the right size.  How can I ensure the final model is correctly sized.  Lots of questions but we really are very excited with the results.
« Last Edit: July 28, 2016, 10:41:22 AM by 10kclockman »

ekbmuts

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Re: 8mp iPhone results - Promising start but....
« Reply #1 on: July 31, 2016, 01:54:46 AM »
10kclockman,  I'd say that the higher your resolution, meaning, the more megapixels you have, the more detail you will get in your final model.  I would lean toward a professional camera, were I you.  I've never used an iPhone for this sort of thing but I wouldn't call it a pro camera.  It's nice, but it's not pro.  You want a camera that you can control in terms of shutter speed, ISO and aperture, not to mention white balance.  And you want to shoot RAW and then convert to TIFF before you go into Photoscan.  That way, you get the very highest quality that is available.

Now, you don't HAVE to have any of this.  Clearly, you can use an iPhone and get a decent result.  You've proven that.  But you asked about improving quality so that's my 2 pence.

Furthermore, the more you fill your frame with your subject (in your case, a human hand), the better your quality will be.  That is, get right up close to that guy.

As well, the stiller that hand stays the better.  A movement of 1/2" will ruin your model.  So that rig sounds interesting.  Just make sure you can remove it in the final model. 

As far as scale goes, print out a scale sheet.  I posted one on this forum recently that a student named Samantha Porter made.  Put that under your hand.  It has measurements written on it so when you get into Photoscan, just make some scale bars based on the sheet (it needs to be in your photos of course) and you're all set.  Search my posts on this forum to find it or Google Samantha Porter.  I can't remember what her website is.  But she's the only Samantha Porter out there doing photogrammetry, of that I'm pretty sure.

That's my input.  I'm fairly new to all of this but I have shot human faces and gotten admirable results.  So it's not like I'm just guessing.  There are many other people who could also comment that have far more experience and information than me.  But no one had piped up yet when I saw your post so I figured I would.

Jon

10kclockman

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Re: 8mp iPhone results - Promising start but....
« Reply #2 on: July 31, 2016, 01:22:48 PM »
Dear Jon

Thank you for your very informative response.  I will definitely follow up on the posts on the scale as I need to get accurate models.  Yes of course higher resolution cameras would be beneficial but I did start this work with a Nikon D750 full frame camera with a lovely lens.  I did get good results but I thought I would try with the iPhone because I am trying to get a system that will be available to clinicians without investing in $2000 + cameras.  I was pleasantly surprised with the outcome.  I also found an app that enables you to output from the iPhone as raw and fix the exposure and focus, so I am keen to keep working with the iPhone.  I really appreciate your response as I am sure you will agree, this is quite a lonely place to develop with such extremes in kit setup.  From massive cave systems with 100 dslrs to people scanning from drones.  Close up work is specialised and there is little out there to help.

Jonathan

ekbmuts

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Re: 8mp iPhone results - Promising start but....
« Reply #3 on: August 01, 2016, 12:51:59 AM »
Jonathan,  Yeah - brave are those who venture into photogrammetry...  And I admire your efforts to make this simple and inexpensive.  If it works, it works, right?  It really doesn't matter who says what.  If it passes the "does it work" test, then power to you.

But I did have one question: you said you'd built a turntable rig for hands.  How do you get the whole body to turn with the hand?  Or do you detach the hand from the unfortunate/unlucky patient, shoot it on your turntable and then reattach it when you're all done?   :)

Just curious...

Jon

10kclockman

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Re: 8mp iPhone results - Promising start but....
« Reply #4 on: August 01, 2016, 01:18:37 AM »
Hi Jon

No I do not intend to sever the hand to scan it!  The turntable allows the hand to be scanned whilst still attached to the body.  I mount the iPhone on the turntable (actually I have just built the mount to hold two iPhones) and rotate around the intact arm.  Picture below.

I am also including lighting but need to diffuse the light source as it is too intense.

Will post some developments as they occur.

Jonathan
« Last Edit: August 01, 2016, 01:25:16 AM by 10kclockman »

ekbmuts

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Re: 8mp iPhone results - Promising start but....
« Reply #5 on: August 01, 2016, 03:44:47 AM »
Pretty cool!

Good luck to you!

Jon