Photogrammetry Prime Lenses vs "default" zoom lenses...? EXAMPLES of scans?

Jonathan85

Hello

I was wondering, i have heard that prime lenses (=fixed focal lenght= you cannot "zoom" - for example just 50mm) have superior visual quality in comparison to "zoom lenses" (lenses that have variable focal length, for example from 18mm to 55mm) and probably even more superior visual quality of the final photos in comparison with the DEFAULT KIT ZOOM lenses you get with most cameras (for example i got the kit lens 18-55mm that came "default" with my Nikon D3200 camera).

Questions:

1) Is that true?
2) Have anybody did comparison "studies" Prime ("fixed") lens (for example 50mm)  vs kit zoom lens (18-55mm for example and set to 50mm)... Have anyone tested this? Took two series of photos with both lenses and then made the whole process of photogrammetry and get a resulting final Mesh with texture...? How did it compare...? Do you have pictures...?

I would love to see picture of these comparison - how much better the model really is if u use prime lenses... How much more detail it has, how much realistic it is, how much "sharper" (and not "blobby") the final mesh is...? Have anybody dont such test and wrote an article or would share such pictures please...?

Jonathan85

Noone :-)...?

gnoop

I never did an exact comparison  but my guess  you would be perfectly fine with  your default  zoom lens once you   are not actually using zoom within a single photo series.         Any time I tried to use  varying focal distance photos   it always ended  in artifacts or interruptions in point cloud generated .    Reality capture would be matching  few initial pictures of same focal distance and then just ignore all the  next photos after a first one with different zoom factor.     Or even if they are still included   you get  shifted  stepped surface sometimes ripped in parts  .     

it's just much  safer  to shoot with same  zoom.   You may shoot another series with other zoom.

As of getting sharper geometry details it totally depends on how sharp your pictures are.   including in corners.   Prime lenses sometimes  but not necessarily  provide you with slightly better sharpness.  Let you squeeze out a tiny bit more.  But you wouldn't beat 50mpix camera anyway 

Still the most decisive factor on sharpness would be lighting conditions and how short exposure time you could do with half closed diaphragm .  Like 1/350 sec with f8  or even f11 aperture  without too much of an  image noise.   Considering you would  want to shoot at  dim cloudy days mostly.  

gnoop

Those blur lab tests I found at imagine-resource  shows that while $1k prime lens (right)  demonstrates amazing sharpness at f4   when it comes to f16, the  actual aperture you would use for photogrammetry  series.  it's kind of other way around and zoom lens have a slight edge over prime one.

https://www.imaging-resource.com/lenses/nikon/24mm-f1.4g-ed-af-s-nikkor/review/

Jonathan85

gnoop said:

Those blur lab tests I found at imagine-resource  shows that while $1k prime lens (right)  demonstrates amazing sharpness at f4   when it comes to f16, the  actual aperture you would use for photogrammetry  series.  it's kind of other way around and zoom lens have a slight edge over prime one.

https://www.imaging-resource.com/lenses/nikon/24mm-f1.4g-ed-af-s-nikkor/review/

LOl thanks... thats quite unexpected... a lot of people spout out (talk nonsense without thinking of testing it themselves) that prime lenses are better even for photogrammetry...

LOL... who knew its not the case...? :-)

Could your example be just one of? Like that it applies only to the specific lenes listed...?

gnoop

Jonathan85 said:

Could your example be just one of? Like that it applies only to the specific lenes listed...?

I have not that much of personal experience with different lenses.   But I find info  published by the site quite credible  as well as   their test image comparison.    . You could check it yourself .

Just keep in mind that  what you see in test pictures done of tripod in studio lighting  is not what would you get of hands in a field.

I myself  bought Sigma foveon matrix camera few years ago  based on this comparison:  

https://www.dpreview.com/reviews/image-comparison/fullscreen?attr18=daylight&attr13_0=sigma_dp2q&attr13_1=apple_iphonex&attr13_2=canon_eos6dmkii&attr13_3=sony_a5100&attr15_0=jpeg&attr15_1=jpeg&attr15_2=raw&attr15_3=jpeg&attr16_0=100&attr16_1=32&attr16_2=100&attr16_3=100&normalization=full&widget=1&x=-0.6429520051460113&y=0.30085844710796533

it  does  this super sharp things only with ideal lighting and 100 iso.    0nce it's dim enough to avoid harsh contrast shadows it's  getting  terrible  starting from 400 iso .   And camera buffer is so shallow you have to wait two minutes after each  8-9 shots, it's getting to hot after 30 shot and drains its battery like a hog.

A company I worked for used  a Canon prime lens   for a while.      It had same traits :    amazing sharpens with half-open aperture.

   It does help you to squeeze  out some extra from  flattish subjects :   ground surface, walls  etc   where deep DOF  is not that necessary  because   anything in focus in  5 cm depth is  basically ok.   

  But once u need to do some really 3d subject you have to close your aperture and  tinier the hole is  softer it becomes.   Not because of light diffraction only  but just because it starts to suffer from a lack of light and high iso numbers.    After f8 it's hardly any difference kit lens or not.

 

I mean a prime lens still has some virtues for certain subjects.