Help With Focus Stacking

ianbarber

ianbarber

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Ian
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Im trying to do some focus stacking to extend the depth of Field but I need to advice.

I understand that you need to take several shots, each time moving the focus point to a new position without moving the camera or zoom on the lens.

The issue i am having is that on my Nikon D3s the focus point does not extend all the way to the bottom.

Am I doing something wrong?
 
It sounds like you've got the basic concept a little confused Ian....or at least very different to my approach (I'm assuming macro here and not landscape).

Focus on the nearest point of your subject and then don't refocus until you've completed all the shots for the stack.
Once you've got the first shot then move the camera forwards slightly and take the next shot....and so on and so on until you have enough coverage of the subject. The forward moves should be along the optical axis.

Bob
 
ianbarber said:
So in fact I am actually moving the camera forward slightly and re focusing until I have covered the entire subject.

Have I got this right?

Ian
Click to expand...

No Ian, not quite.

Focus only once....at the nearest point of your subject. Moving the camera forwards will then move the subject plane forwards and a new part of the subject will be in focus. Keep moving and shooting until you reach the end of the subject.
Don't change the focus after making the first shot....just move the camera.

Bob

Edit....an example in a parallel universe

A golfer lines up 10 golfballs and intends to practice driving. If he was "focus stacking", he would make the same swing each time but shuffle forwards a distance equal to the spacing between the balls....that's what you want to do.
 
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are you sure?

I thought you just focused on wherever you wanted the focus to start on the subject, then leaving the camera in place, move the focus dial a little each shot. This moves the focal point further across the subject. Surely thats what the distance markings on the focus dial mean, each time you move it, the point at which the lens is focused moves in and out of the scene.
 
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essexash said:
are you sure?

I thought you just focused on wherever you wanted the focus to start on the subject, then leaving the camera in place, move the focus dial a little each shot. This moves the focal point further across the subject. Surely thats what the distance markings on the focus dial mean, each time you move it, the point at which the lens is focused moves in and out of the scene.
Click to expand...

This assumes there's no focus breathing on the lens (this is where the magnification changes slightly at the same focal length but different focus). Very few lenses have no focus breathing at all, and focus stacking will highlight even a tiny bit.
 
Makes sense. But if you have you camera on a tripod, how do you ensure a) you move it all in the same plane each shot and b) you have to move all that a few mm at a time?
 
essexash said:
are you sure?

I thought you just focused on wherever you wanted the focus to start on the subject, then leaving the camera in place, move the focus dial a little each shot. This moves the focal point further across the subject. Surely thats what the distance markings on the focus dial mean, each time you move it, the point at which the lens is focused moves in and out of the scene.
Click to expand...
Most modern macro lenses utilise internal focus and the focal length will reduce as you focus closer to the subject. Canon's 100mm macro is only 78mm at MFD. Using your suggested method would also change the FoV of the lens and distortion would start to occur....more so if there was a larger distance between the close focus point and the far focus point.

Bob
 
essexash said:
Makes sense. But if you have you camera on a tripod, how do you ensure a) you move it all in the same plane each shot and b) you have to move all that a few mm at a time?
Click to expand...
That's where the focus rail comes into play.....just crank the whole lot forwards in steps and along the optical axis (as mentioned earlier)

Bob
 
An example.

Focus on the nose and then without refocusing move the camera forward 5 times so that the last shot has the rear wing tip sharp (or as far as you want to go). This gives a 5 shot stack which when processed looks like this.

 
Is the processing of the 5 shots manual or is it automated with a plug-in or something?
 
When you move the camera forward leaving the focus where it was, doesn't the subject get closer and therefore bigger in the frame? Auberge the software compensates for that?
 
that must of been a very patient fly :) i might try and price up one of these rail things.
 
Southdowns said:
When you move the camera forward leaving the focus where it was, doesn't the subject get closer and therefore bigger in the frame? Auberge the software compensates for that?
Click to expand...

If you don't refocus then the magnification doesn't change. A different part of the image will now be in focus with the same magnification as the focussed part of the previous shot. The stacking software will pick the "sharp" parts of each image and combine them.

Bob
 
Mike, that is a fantastic shot, especially as it was done handheld. I'm thinking of getting a cheap focus rail to see if I get on with it and then getting a better one if I enjoy shooting with it. I wouldn't even dream of doing it hand held though.

I usually shoot at between f8 and f11 on my 100 L macro and get some reasonable DOF, but I've been thinking of stacking for a while.
 
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