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Photogrammetric, Oblique Image Stitching, Pets Dressed in Clothes Photos… this is a place to chat and share stories with your fellow Photosynthers. Not all topics have to be about photography, this is a place to relax and chat about whatever you fancy.


Topic: Aperture and Resolution Test

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PGRic (Over 1 year ago)
Aperture, Size test.

I carried out a little non-scientific experiment the other day trying to determine whether aperture and resolution impacted on point cloud density. Having previously read about images being converted to1.5MP (aaprox) the resolution trial was a knowingly pointless addition…but it was thrown in anyway.

First, a subject with oodles of variance in visible texture (hopefully, this explains the cushion and frog) was set up. Because the test was being conducted indoors, a tripod was used to minimise the effect of ISO setting (400) and shutter speeds needed for the extremes of aperture. An image was taken with each of the 4 settings below, before the tripod and camera was moved to the next position: 

Setting 1:	Res: 3008 x 2000	Ap: F22	shutter 0.8-1.6sec
Setting 2:	Res: 3008 x 2000	Ap: F3.5	shutter 1/30-60sec
Setting 3: 	Res: 1504 x 1000 	Ap: F22	shutter 0.8-1.6sec 
Setting 4: 	Res: 1504 x 1000 	Ap: F3.5  	shutter 1/30-60sec

cont below
PGRic (Over 1 year ago)
My equally non scientific observations from this test were:

Images taken at F22 (setting 1&3) do appear to have a slightly denser point cloud centrally, but it’s almost negligible. However, the outer edges of the F3.5 synths have significantly more visible points. 

As anticipated, resolution doesn’t make any difference apart from the ability to zoom. 

No difference in point cloud density between the 250 & 100 dpi synths
Pierrot21 (Over 1 year ago)
I would write it different:

Photosynth is very, very good to balance light and colours; I would like my usual softwares for panoramic view could work the same (photostitch, autostitch and other); So, don't care about aperture und use an automatic program; just change the ISO if you are working inside and have no tripod.

I just made a test because I was disapointed by a point cloud: that is:
outside (garden, architecture, monuments) my pics are 1600 x 1200 (2 MPixels) and before synthing I divide them by 4 (that is 50% on each side) to 800 x 600 (1 minute for a 100 pics with PhotoshopElements); that's enough for a nice visit, or for the view on a computer screen; and I have no more memory-problem and it's so much FASTER for merging the pics and for uploading them ...

So now have look on my CITYGIRL (search this tag) and view the difference: not so much in the normal view but a much better cloud.
Pierrot21 (Over 1 year ago)
...
The resolution (100 or 250 dpi) is impoetant for printing; on a screen just look for the number of pixels (or dots, or points ; I'm not sure about the english word)
PGRic (Over 1 year ago)
Hi Pierrot, you’d have to keep an eye on exposure times indoors…anything below 1/60 might impact on image sharpness. I suppose the next question is; does image sharpness alter the outcome of a point cloud density? ….sounds like another test

Yes the point cloud is definitely improved on the hi-res version. 

Love the dragon synth, looks like he’s flown off on the point cloud :)
PGRic (Over 1 year ago)
oooppps forgot to add, you might be right abou the light, the F22 images are obviously brighter and being able to see the object may account for a few extra points.
Pierrot21 (Over 1 year ago)
I just finished a new experiment with a crazy dragon (tag 'reddragon' in one word). I had never seen such as reddragon-1 , 100% synthy but awful. I then took the background away and it's working much better in 2 parts and 2 nice clouds (reddragon-2); we know this problem: the program is working good on the long sides of an object, but not on small sides like the head or the bottom in this case. OK
What is now interessant: I resized all the pictures close to the dragon, so they all are different in dimensions; and it's working the same (not better, but not worse). Another good point for Photosynth!
Do you agree happy dragon-killers? ;-))
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