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Author Topic: Photography Tips  (Read 7538 times)

Mickman

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Photography Tips
« on: May 07, 2013, 04:51:56 PM »
This is my first post & so I have a few questions.

1.)  when shooting an object is it best to move the actual camera around the object or is it possible to place the object on a turntable and keep the camera stationary on a tripod ?     

2.) background noise:   What techniques are users employing  to eliminate  background ? 
     -  I was thinking since my objects are no larger than a shoe..  I could create an arm that extends from the camera to approx. 50cm beyond the target object & attach a white board to it.   Currently I have my friend walk slowly behind the object with a large white card.   its an ok technique but I'm sure my friend won't be this co-operative after 50 photo shoots  :)

3.) Masking backgrounds in Agisoft:   Is the only method of masking backgrounds manually ?  Is there a way to batch process this operation after masking one image ?      Masking 100 + images  by hand would take forever....

4.)  I followed the Agisoft PhotoScan tutorials ... but there's nothing related to "Chunks "  Are chunks an important aspect of the process ?   

5.)  Best camera ?    so for I've tested an iPhone 5  which worked quite well... & a Canon EOS 550D which in Raw image mode... which takes great pix but hogs loads of memory.     

6.)  Calibration software... is this required before I start the  Agisoft PhotoScan  ?

 


RalfH

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Re: Photography Tips
« Reply #1 on: May 07, 2013, 06:06:55 PM »
Hi Mickman,

a few short answers:

1.) Turntable is o.k. The only thing that's required is that the camera moves relative to the object, no matter which part is doing the actual moving.

2.+3.) Masking. Several options for this; either in Photoscan or creating a mask externally and importing it. Some hints by Alexey in this thread: http://www.agisoft.ru/forum/index.php?topic=1087.msg5396#msg5396, and probably also in others.

4.) The only reason for using chunks that I see (there may be others) is to split a really huge project (thousands of images) in smaller parts for processing.

5.) Anything goes; this really depends on your requirements. Images from many most consumer video cameras or cameras without mechanical shutter (including cell phones and GoPro) can be problematic.

6.) No pre-calibration needed. If you work with cameras in which parts of the lens move between images (autofocus, zoom, optical image stabilisation), changing camera calibration setting to separate instead of groups imroves 3D modelling quality.

7.) Have fun.

Alexey Pasumansky

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Re: Photography Tips
« Reply #2 on: May 08, 2013, 02:37:24 AM »
Hello Mickman,

I think that Ralf has already answered your questions, however, I have several comments:

1. Both ways are OK. But you should make sure that object geometry doesn't change during the capturing scenario, for example, when using a turn-table option for soft object type. Also please note that using turn-table always require background masking, but in this case you can use mask-from-background option (providing that camera position is fixed) - the requirement is to capture a single shot of the background without the object.

5. DSLR cameras a preferred. But if you are achieving acceptable results with current camera, there is no need to change anything unless you expect result improvement.

6. Since the image EXIF contain focal length and sensor size there is no need to pre-calibrate camera.
Best regards,
Alexey Pasumansky,
Agisoft LLC

David Cockey

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Re: Photography Tips
« Reply #3 on: May 08, 2013, 09:06:52 PM »
I have found a background with good texture can be beneficial during the align stage, particularly when the object of interest does not have a strong texture. The one requirement is the object of interest does not move relative to the background. Using the background during align.

The only time I have masked the background was when the object of interest moved relative to the background.

For build geometry I orient and set the "box" close the object so that little or no geometry is created from the background.

RalfH

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Re: Photography Tips
« Reply #4 on: May 09, 2013, 12:49:35 PM »
I agree with David that this can be very helpful for objects with poor texture (but not for the turntable setup). I sometimes find it a bit annoying to search for my object inbetween everything else though; then I mask the background.