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Author Topic: Question about source image blur and corner softness.  (Read 2974 times)

Jenovation

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Question about source image blur and corner softness.
« on: August 17, 2016, 08:07:02 PM »
So we know perfect sharp pictures lead to the best scans and textures, however I am wondering about corner blur or softness (or DOF).

I am currently shooting pretty flat surfaces with an A7RII and 35mm lens, images are very sharp but there is still a slight noticable softness difference between image corners and image center.

So I am wondering, does PS prioritize information in the frame center for mesh building and texture processing over image corners? How likely is it that softer corners will cause imperfections in the scan or texture blur, and should the images perhaps be cropped a little to get rid of this problem?

Any information would be helpful!


Thanks.

MeHoo

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Re: Question about source image blur and corner softness.
« Reply #1 on: August 18, 2016, 03:21:51 AM »
Are you using the Sony 16-35mm lens?  I have also noticed quite a bit of softness in the corners with this identical setup.  My scans seem to come out just fine in the end though.  One thing you should try to avoid is taking "glancing angle" shots.    As that seems to produce a lot of pixels that are "sharp enough" compared to typical megapixel cameras. You can see this after you generate and look at the tie points.  Some that are not great are pinned.  I have no information, however, if these are just used to help alignment as a "lesser" quality (worst-case if no other exists), kinda like the "estimate image quality" stage estimates things.. I'd hope so.

Still trying to figure some of these inner details, myself.

Jenovation

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Re: Question about source image blur and corner softness.
« Reply #2 on: August 18, 2016, 03:31:56 AM »
Thanks for the response. What do you mean exactly with 'glancing angle' shots?

And yes, using the 16-35mm. I think the 35 prime lens would be the better option but dropping 1,5k is not an option right now. I am actually currently using the in camera crop (which emulates a crop sensor I guess) and there is little to no softness, but ofcourse pics are lower res and more need to be taken... kind of beats the purpose of using an 8k camera.

Glad to hear your scans turn out fine though, have you noticed any blur patches in your textures?

MeHoo

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Re: Question about source image blur and corner softness.
« Reply #3 on: August 18, 2016, 03:35:59 AM »
Yep.. Textures are the Bain of my existence.. Trying to figure out how the dense cloud can look amazing, but the resulting textures are soft.. I tried even disabling all but the best shot for that area.. Terrible results.

It's not THAT frequent, but the results are really upsetting.

Go into Mari, paint it manually,I guess.. Frustrating.

Glancing, meaning.. Not perpendicular... Photoscan seems to still use these..

Jenovation

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Re: Question about source image blur and corner softness.
« Reply #4 on: August 18, 2016, 03:41:56 AM »
So I guess you are scanning objects? With surfaces it's pretty easy to have the camera perpendicular and it seems you dont need angled shots for good scans, which reduces the corner issues (you're probably getting corner softness with added DOF?)

Just finished a test with the cropped textures and they look great so far (shot at 50 ISO f11) but  I will inspect them closer to see if there are blurry patches.

It'd be great if Agisoft could assume the center of the photo is the sharpest and never use corner information for texture building, however it still doesnt address the soft corners causing inaccuracies in the scan..
« Last Edit: August 18, 2016, 03:44:52 AM by Jenovation »

MeHoo

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Re: Question about source image blur and corner softness.
« Reply #5 on: August 18, 2016, 03:49:14 AM »
It just might.. I am unsure. 

The model is sharp as hell, but when it gets to the texture it gets soft.. I don't get how the data can create a sharp model, but the texture gets soft.. makes me wonder where the disconnect is.

I am not using the crop, but I am contemplating it because of the slowness of the internal memory on this camera.  I can't continually shoot one-frame at a time for more than 20 or so photos before the internal memory just dies on me.. so frustrating because this sensor is AMAZING.

glancing angles are usually from other angles for detail in certain areas (I shoot a lot of urban decay with crumbled bits I get real close to, which means at f/14 or so, the background is still being aligned using those photos.  I would KILL for a depth sensor like a light field camera, and just auto-mask those points.  I am unsure, but I am hoping Photoscan is doing that internally for the mesh generation, but the texture.. obviously not. 

All I know is.. I've seen some REALLY weird results that just don't add up.

And yeah.. Sony glass is stupid expensive.  Coming from Canon, owning 400mm lenses, etc.. I am pretty upset at the lack of quality for the price.  That is another debate.  I picked up the Metabones adapter, and I want to see if Photoscan handles it well without a grid being shot.  I still have my 5DMIII's 24-105.  I will do a test soon.

stihl

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Re: Question about source image blur and corner softness.
« Reply #6 on: August 18, 2016, 09:54:00 AM »
What kind of texture size and count are you guys using for the texture generation?

MeHoo

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Re: Question about source image blur and corner softness.
« Reply #7 on: August 18, 2016, 03:07:45 PM »
I am using 250ish 42mp images.  Tiff, 16bit, uncompressed.  He said he's using the crop in the camera, so that's different.