Gigapan pro and AF - need advice.

[henrikfoto]

I just bought a Gigapan Pro and have started testing.
I know the most normal is to set the focus manually
in case the cameras af can't find enough contrast in some of the
pictures and then don't make a picture.

But I am trying to find a way to use af in all the pictures.
I have been testing with a Nikon D800e and a micro-nikkor 200.
In about 10% of the pics the camera coudn't fire.

Do anybody have a good idea what lenses have a better af
and might be able to hit every pic?

Or maybe Canon have better af for this?

Henrik

[michael]

Henrick,

It's seems that you are chasing an impossible goal.

Imagine a landscape shot with sky. What will the camera focus on? Blank sky (assuming no clouds for the moment) is impossible for an AF system to handle.

Michael

[henrikfoto]

Henrick,

It's seems that you are chasing an impossible goal.

Imagine a landscape shot with sky. What will the camera focus on? Blank sky (assuming no clouds for the moment) is impossible for an AF system to handle.

Michael

Maybe, Michael. But in many cases there is some contrast in the sky. And what lenses/systems are best
at finding the small contrast and making the shot?

Or it possible to program a camera so that if the af don't find contrast it will go to infinity and make the shot?

[Bart_van_der_Wolf]

But I am trying to find a way to use af in all the pictures.

Hi Henrik,

Why would you want to do that?

Cheers,
Bart

[henrikfoto]

Hi Henrik,

Why would you want to do that?

Cheers,
Bart

Because I am trying to get all in focus. Both all levels of the foreground and the background.
Just experimenting😊 Nobody have an idea ?

[kencameron]

I have had some success using autofocus where there is detail and contrast and pausing the gigapan to switch to manual focus when there is isn't - and then switching back again. Not what you want, but I don't really see how you could get any closer. Autofocus surely needs something to focus on.

[henrikfoto]

Ok, thats a good idea!
I will try that tomorrow.

What camera and lenses do you use?

[kencameron]

I have the entry level gigapan which I use with an old  12mp micro 4/3 camera - olympus e-pm1 - which lives on the gigapan, and a 45mm (90 equivalent) lens or occasionally a 40-150 zoom.

[robdickinson]

shoot 2 sets, foreground and background , and merge the results. Or pause and change - of you do this and change the scheme to rows starting at the bottom (or top) you can change it once possibly.

[henrikfoto]

shoot 2 sets, foreground and background , and merge the results. Or pause and change - of you do this and change the scheme to rows starting at the bottom (or top) you can change it once possibly.

Thank you!
That is a good idea.

[Bart_van_der_Wolf]

Because I am trying to get all in focus. Both all levels of the foreground and the background.
Just experimenting😊 Nobody have an idea ?

How about focus stacking?

Cheers,
Bart

[henrikfoto]

How about focus stacking?

Cheers,
Bart

I guess that would be possible, but if a large panorame contains 100 shots of each 100 mb I think my Mac
will start crying

[hjulenissen]

If you are constrained on raw stitching, perhaps you could make some pre-processing script (perhaps looking at only jpegs) that would eliminate raw files that are deemed to be redundant (i.e. not sufficiently different from images shot at neighbour focusing distances). Don't know if such a thing could be worthwhile.

If you are constrained on recording time, things are a bit harder. You want to step the focus at some number of steps between some close and far focus limit based on image data (for each part of the scene). Sounds like a really advanced CDAF/PDAF<->focus bracketing algorithm. Did you check out what the MagicLantern guys are doing to Canon DSLRs?

If you are in the neighbourhood of 100 positions, and need the accuracy of 100 focus points, perhaps it would be worthwhile to do some manual testing. Tilt your camera towards the significant object that seems closest and check the (manual/auto) focus value. Do the same to the significant object that is farthest away. Consult DOF data/lens data for the chosen aperture to calculate the number of points needed in-between. Then do the whole scene using those focus points (might still cause redundant data, though).

-h

[allegretto]

this will show how much I don't know, but

due to proportions, don't you almost always use a wider-angle lens for panos? If so, after about 4.0-5.6 just about everything IS in focus, no?

[D Fosse]

You don't use wide angle because the distortion would quickly become totally unmanageable.

In terms of geometry, a stitched pano made from, say, 85mm shots is perfectly equivalent to a single, say, 20 mm shot. You still need those stretched corners (in the final result) to maintain straight lines.

[kencameron]

How about focus stacking?

What would be the advantage of focus stacking, in a many-panelled high-resolution pano, over autofocus for the panels where it works and manual focus where it doesn't? I would be interested in trying it if I thought it would produce a better result.

[Bart_van_der_Wolf]

What would be the advantage of focus stacking, in a many-panelled high-resolution pano, over autofocus for the panels where it works and manual focus where it doesn't? I would be interested in trying it if I thought it would produce a better result.

Hi Ken,

With Auto Focus some of the tiles will be wrong (wrong subject/distance focused) or the tile can be missing (no focus acquired). With manual focus one can do several runs of the scene, while having consistent focus per run and more DOF than would be possible with a single run.

The downside is the huge number of files one will accumulate, and it may require some additional work getting the focus stacks prepared before stitching the pano.

Cheers,
Bart

[robdickinson]

this will show how much I don't know, but

due to proportions, don't you almost always use a wider-angle lens for panos? If so, after about 4.0-5.6 just about everything IS in focus, no?

Aye the point og a gigapan is to produce higeh resolution files using longer focal lengths which tend to be optically better.

Another point to watch is changing focus can affect field of view, probably not so much with a prime but may make stacking individual images trickier.

[kencameron]

Hi Ken,

With Auto Focus some of the tiles will be wrong (wrong subject/distance focused) or the tile can be missing (no focus acquired). With manual focus one can do several runs of the scene, while having consistent focus per run and more DOF than would be possible with a single run.

The downside is the huge number of files one will accumulate, and it may require some additional work getting the focus stacks prepared before stitching the pano.

Cheers,
Bart

Interesting. The other downside of doing several runs of a multi panel pano outdoors would be changes in the light and movement of shadows and clouds. This can already be a problem with single runs. I might give it a try indoors. Have you tried it yourself?

[Bart_van_der_Wolf]

Interesting. The other downside of doing several runs of a multi panel pano outdoors would be changes in the light and movement of shadows and clouds. This can already be a problem with single runs. I might give it a try indoors. Have you tried it yourself?

Hi,

Yes, changing light conditions will be an issue with large gigapixel scenes. The shooting order can be important, column by column or row by row, zigzag, or always left to right or right to left (depending e.g. on the movement of clouds and windspeed). Other than using cameras with lots of pixels per shot (which will reduce the number of tiles needed), I therefore usually prefer to take multiple bracketed shots per tile (usually exposure brackets for HDR scenes), instead of multiple scenes. Doing focus bracketing will require different tools, and I'm not familiar enough with the Gigapan software to know if it supports that. It also depends on the camera model if focus can be controlled easily and accurately enough for bracketing.

To avoid such issues, I may use tilt and shift lenses, but I'm currently limited to 90mm focal length. For some scenes, the tilt will allow deep DOF, but not all pano stitchers can deal with images that were optically decentered. That will amount to a lot of manual post-processing intervention on huge projects.

I'm currently not doing Gigapixel projects (I do more resolution enhanced shots of normal to slightly wide scenes/objects), but if the need arises I'll have to take the specific shooting conditions as leading me to an approach. There is no universal solution. Some scenes are 'easy' with lots of detail to (auto)focus on, others have foreground and background detail (may require manual focus brackets), others have occlusions (causing issues with fuzzy edges where DOF allows to see the background partly through solid objects in the foreground), others have featureless areas.

Cheers,
Bart