Practicing The Craft: Stone sculptor take 2 ~ a 43 frame stack

[JBW]

You have seen these stones before. This time it is a forty-three frame focus stack. I set the camera to ISO 100, F/14, 1/6s shutter speed and multi segment zone focus. Using the focus magnifier I zoomed in on forty-three separate areas. Making sure that every area was sharply focused and overlapped with its neighbors.

Once back at the computer I down-loaded into Capture One Sony Pro. Some adjustments on all forty-three and export into Fiji. In Fiji a stack with just a touch of unsharpen mask.

Back into Capture One. A hint of yellow to enhance the bamboo. Individual layers for the grass, stones and background adjustments. Finally some overall adjustments to bring a little unity to the shot.

[JohnRostron]

Brian. What you have done is clearly effective. I cannot see any unsharp areas in your final image. My camera, a Sony A55 is very much like yours and I could do the same thing should I wish. I woud, however, have done the stacking in a different way. For my tabletop stacking macros I use lens-barrel focussing. I focus first on an artefact (typically a ruler) placed behind the subject and note the outer distance. I then do the same for the ruler in front of the object. I then take shots with my infra-red remote and adjust the focus each time till I reach the outer distance. Adjusting the lens barrel is fiddly, so I have made a couple of card disks which fit around the static and rotating part of the lens barrel. I can then change focus by rotating the one card against evenly-spaced markers on the other.

What do you, or others in CiC, think of the merits (or otherwise) of these two techniques.

John

[JBW]

Brian. What you have done is clearly effective. I cannot see any unsharp areas in your final image. My camera, a Sony A55 is very much like yours and I could do the same thing should I wish. I woud, however, have done the stacking in a different way. For my tabletop stacking macros I use lens-barrel focussing. I focus first on an artefact (typically a ruler) placed behind the subject and note the outer distance. I then do the same for the ruler in front of the object. I then take shots with my infra-red remote and adjust the focus each time till I reach the outer distance. Adjusting the lens barrel is fiddly, so I have made a couple of card disks which fit around the static and rotating part of the lens barrel. I can then change focus by rotating the one card against evenly-spaced markers on the other.

What do you, or others in CiC, think of the merits (or otherwise) of these two techniques.

John

I be curious as well. My first thought is it is a bit of apples and oranges. Your technique was developed for indoor tabletop macro and I'm working at a distance of two to three meters outdoors. I'm not even sure i could get a ruler to stay put on the stones

[Stagecoach]

What do you, or others in CiC, think of the merits (or otherwise) of these two techniques.

John

I be curious as well. My first thought is it is a bit of apples and oranges. Your technique was developed for indoor tabletop macro and I'm working at a distance of two to three meters outdoors. I'm not even sure i could get a ruler to stay put on the stones

Ok here's my thoughts ...........................

Firstly, Brian you have achieved a very good result with the method you used and as a practice of 'focus stacking' with 43 frames well done ! But, I believe you have put more effort into this than you may have needed and your method has added a certain amount of risk.

Your technique was developed for indoor tabletop macro and I'm working at a distance of two to three meters outdoors.

I would not agree with that statement Brian in the context you have used it. All focus stacking is the collection of a number of frames (slices) that have a % of overlap of the 'in focus' depth and this applies whether a small object close, your example or a landscape. For example, John's technique would have worked well here as would your technique (if you were lucky) on a small tabletop object.

The 'risk' I refer to Brian is that in selecting your 43 individual points to focus on there would have been no way of you ensuring these had the % in focus overlaps required and that you had not missed some out. The reason I suggest you achieved such a good result was because of the DoF at the parameters you used. For example, 90mm at f/14 at a subject distance of 3m gives a DoF of 620 mm and as your subject distance increases so does your DoF (at 4 m dist the DoF would be 1.1 m).

If you had used the focus barrel method you could have had your first focus point lets say 300mm (on the grass) in front of the rock and the last on the farthest shrub and divided this into the number of frames needed based on the overlap and known DoFs. The number of frames would have been significantly less and the result guaranteed.

When you get to practicing with closer subjects DoFs become much smaller and the discipline and procedure for ensuring you have adequate 'overlaps' becomes far more critical and it's very unlikely that you will get such good results using the method you have here.

[JBW]

Ok here's my thoughts ...........................

Firstly, Brian you have achieved a very good result with the method you used and as a practice of 'focus stacking' with 43 frames well done ! But, I believe you have put more effort into this than you may have needed and your method has added a certain amount of risk.



I would not agree with that statement Brian in the context you have used it. All focus stacking is the collection of a number of frames (slices) that have a % of overlap of the 'in focus' depth and this applies whether a small object close, your example or a landscape. For example, John's technique would have worked well here as would your technique (if you were lucky) on a small tabletop object.

The 'risk' I refer to Brian is that in selecting your 43 individual points to focus on there would have been no way of you ensuring these had the % in focus overlaps required and that you had not missed some out. The reason I suggest you achieved such a good result was because of the DoF at the parameters you used. For example, 90mm at f/14 at a subject distance of 3m gives a DoF of 620 mm and as your subject distance increases so does your DoF (at 4 m dist the DoF would be 1.1 m).

If you had used the focus barrel method you could have had your first focus point lets say 300mm (on the grass) in front of the rock and the last on the farthest shrub and divided this into the number of frames needed based on the overlap and known DoFs. The number of frames would have been significantly less and the result guaranteed.

When you get to practicing with closer subjects DoFs become much smaller and the discipline and procedure for ensuring you have adequate 'overlaps' becomes far more critical and it's very unlikely that you will get such good results using the method you have here.

Okay Grahame. Reality clicks in. If I am going to use a focus barrel method I will need some way to accurately measure how much I move the barrel?

My handyman skills were never much and are now non existent. This to me means I would need either geared head of some kind or a focus rail?

Once I do the math and set the first shot. it is simply a question of snapping and moving the rail or geared head the proper amount?

This is easier and safer because I don't more my focal point as I now do but rather my focal plain?

Have I got a basic understanding of your explanation?
Brian

[Manfred M]

Brian - focus point(s) is just one of the ways that your camera determines where the focus plane is for a particular shot. The focus plane is the only part of what you are focusing on that is truly in focus. If you are focus stacking, you want a number of focus planes along with areas that are in "good enough" focus (as defined by the dept of field) to build an image.

In this shot, while I understand you are trying to practice focus stacking skills, I would strongly suspect that you can achieve a good, sharp shot by relying purely on DoF.

While I don't do focus stacking, I do shoot panos, which is also a technique where we use multiple images to build up a composite. I have found that "less is more" when doing panos as more data than is absolutely necessary can "confuse" the algorithm and can result in an inferior image than one that uses fewer frames. I suspect that focus stacking might show similar properties. As Grahame points out, more frames also increase the risk of error.

[JBW]

Brian - focus point(s) is just one of the ways that your camera determines where the focus plane is for a particular shot. The focus plane is the only part of what you are focusing on that is truly in focus. If you are focus stacking, you want a number of focus planes along with areas that are in "good enough" focus (as defined by the dept of field) to build an image.

In this shot, while I understand you are trying to practice focus stacking skills, I would strongly suspect that you can achieve a good, sharp shot by relying purely on DoF.

While I don't do focus stacking, I do shoot panos, which is also a technique where we use multiple images to build up a composite. I have found that "less is more" when doing panos as more data than is absolutely necessary can "confuse" the algorithm and can result in an inferior image than one that uses fewer frames. I suspect that focus stacking might show similar properties. As Grahame points out, more frames also increase the risk of error.

Absolutely. Each separate shot showed good sharpness throughout. It was a good training exercise. And I really was curious how solid my new tripod really is. Not moving things while pushing buttons and adjusting focus for 40+ shots indicates to me that it is solid.

[Stagecoach]

Okay Grahame. Reality clicks in. If I am going to use a focus barrel method I will need some way to accurately measure how much I move the barrel?

Ok, let's take this one further and remain with your above rocks exercise, and not get TOO accurate

Let's say the front of the rock is 3 m from the camera and the rear shrubs are 6 m from the camera. That gives you a total depth of 3 m that you want to be all in sharp focus in your finished image.

At 3m using your 90 mm at f/14 there is a DoF of 0.62 m.
You require an overlap of in-focus depth (0.62m) of 20% which means you need steps of 0.49 m.
The total depth you require is 3 m so the number of steps is 3 divided by 0.49 = 6.1. We would round up to 7.

So you now know that 7 steps or a greater number of them is going to give you what you need to get all of the frames overlapping in focus area.

Now the problem comes as to how you physically achieve this, rotating and counting 'serrations'/markings or using a gizmo as John describes (which is simply a physical 'extension' to the serrations method). If I were you I would try this scene again, setting your focus firstly on the bit of rock closest to you and moving the barrel one serration at a time. If your lens does not have these serrations I will happily draw you up a band that you can tape around it with graduated markings that you can print on paper and cut out.

My handyman skills were never much and are now non existent. This to me means I would need either geared head of some kind or a focus rail?

No geared head is required or a focus rail. Besides it would be one heck of a large focus rail for the above scene

Once I do the math and set the first shot. it is simply a question of snapping and moving the rail or geared head the proper amount?

If you have that gear but you don't need it yet. You may recall that crab exoskeleton I posted a few months back, done by rotating the barrel by 1/2 serration increments.

Edit : I believe there will be no need to do any maths as you will eventually learn from experience you simply move by increments of 1/2. 1 or 2 serrations at a specific aperture whether it is for near or far subjects. The maths may come when when you get into micro stacking and are also used by the remote controllers.

This is easier and safer because I don't more my focal point as I now do but rather my focal plain?

I missed this one but Manfred caught it.

Have I got a basic understanding of your explanation?
Brian

I think we are getting there, and there is no need for too much complication.

Look at it practically, if you do a test tomorrow on the same scene, use 2 x serration intervals and after stacking find it was not enough, you go back and do it with 1 x serration intervals

And if you do too much maths it's going to tell you to rotate the barrel something like 2.367 deg after the first shot, then 2.389 after the second up to 7.636 before the last shot and you are going to say

[JBW]

Ok, let's take this one further and remain with your above rocks exercise, and not get TOO accurate

Let's say the front of the rock is 3 m from the camera and the rear shrubs are 6 m from the camera. That gives you a total depth of 3 m that you want to be all in sharp focus in your finished image.

At 3m using your 90 mm at f/14 there is a DoF of 0.62 m.
You require an overlap of in-focus depth (0.62m) of 20% which means you need steps of 0.49 m.
The total depth you require is 3 m so the number of steps is 3 divided by 0.49 = 6.1. We would round up to 7.

So you now know that 7 steps or a greater number of them is going to give you what you need to get all of the frames overlapping in focus area.

Now the problem comes as to how you physically achieve this, rotating and counting 'serrations'/markings or using a gizmo as John describes (which is simply a physical 'extension' to the serrations method). If I were you I would try this scene again, setting your focus firstly on the bit of rock closest to you and moving the barrel one serration at a time. If your lens does not have these serrations I will happily draw you up a band that you can tape around it with graduated markings that you can print on paper and cut out.




No geared head is required or a focus rail. Besides it would be one heck of a large focus rail for the above scene



If you have that gear but you don't need it yet. You may recall that crab exoskeleton I posted a few months back, done by rotating the barrel by 1/2 serration increments.

Edit : I believe there will be no need to do any maths as you will eventually learn from experience you simply move by increments of 1/2. 1 or 2 serrations at a specific aperture whether it is for near or far subjects. The maths may come when when you get into micro stacking and are also used by the remote controllers.



I missed this one but Manfred caught it.



I think we are getting there, and there is no need for too much complication.

Look at it practically, if you do a test tomorrow on the same scene, use 2 x serration intervals and after stacking find it was not enough, you go back and do it with 1 x serration intervals

And if you do too much maths it's going to tell you to rotate the barrel something like 2.367 deg after the first shot, then 2.389 after the second up to 7.636 before the last shot and you are going to say

two it is We've got enough in our lives with all the silliness in the Philippines right now.

[JBW]

Ok, let's take this one further and remain with your above rocks exercise, and not get TOO accurate

Let's say the front of the rock is 3 m from the camera and the rear shrubs are 6 m from the camera. That gives you a total depth of 3 m that you want to be all in sharp focus in your finished image.

At 3m using your 90 mm at f/14 there is a DoF of 0.62 m.
You require an overlap of in-focus depth (0.62m) of 20% which means you need steps of 0.49 m.
The total depth you require is 3 m so the number of steps is 3 divided by 0.49 = 6.1. We would round up to 7.

So you now know that 7 steps or a greater number of them is going to give you what you need to get all of the frames overlapping in focus area.

Now the problem comes as to how you physically achieve this, rotating and counting 'serrations'/markings or using a gizmo as John describes (which is simply a physical 'extension' to the serrations method). If I were you I would try this scene again, setting your focus firstly on the bit of rock closest to you and moving the barrel one serration at a time. If your lens does not have these serrations I will happily draw you up a band that you can tape around it with graduated markings that you can print on paper and cut out.




No geared head is required or a focus rail. Besides it would be one heck of a large focus rail for the above scene



If you have that gear but you don't need it yet. You may recall that crab exoskeleton I posted a few months back, done by rotating the barrel by 1/2 serration increments.

Edit : I believe there will be no need to do any maths as you will eventually learn from experience you simply move by increments of 1/2. 1 or 2 serrations at a specific aperture whether it is for near or far subjects. The maths may come when when you get into micro stacking and are also used by the remote controllers.



I missed this one but Manfred caught it.



I think we are getting there, and there is no need for too much complication.

Look at it practically, if you do a test tomorrow on the same scene, use 2 x serration intervals and after stacking find it was not enough, you go back and do it with 1 x serration intervals

And if you do too much maths it's going to tell you to rotate the barrel something like 2.367 deg after the first shot, then 2.389 after the second up to 7.636 before the last shot and you are going to say

I did give it a go, twice. Didn't work. The first time I tried moving the barrel finger grip groove to finger tip grove on the focus ring. Three shots and I was totally out of focus. perhaps part of the problem is that I am near infinity with my 90?

The second time I tried moving my focus up the center, The outsides never came into focus.

I'll work on it.

[Stagecoach]

Brian, how far is your camera from that nearest rock?

[JBW]

Brian, how far is your camera from that nearest rock?

The shot in this thread was about 2 meters. Today it was a different angle and to get everything in I needed to be about 3.5 meters. Distance may have been the culprit.

[Stagecoach]

The shot in this thread was about 2 meters. Today it was a different angle and to get everything in I needed to be about 3.5 meters. Distance may have been the culprit.

Brian, from the picture of those rocks my estimation is that the depth between the front of the nearest rock and the farthest greenery is about 2 m.

At 3.5 m (camera distance to the nearest rock) the DoF will be 0.85 m at f/14.

You would only be turning the focus barrel a small amount before the entire scene was OOF.

I set up a test with my lens, 105 mm (near enough the same for this). I focused on a point 3 m and on turning the focus barrel 3 'notches'/'grooves' a point at 5 m from the camera (plus all in front of it) was OOF.

The answer here is that at these long distances you need very few shots/intervals over a small depth such as this because of the large DoF. You could use 1/2 divisions.

When you come to shooting things small and much closer you will be able to rotate the lens barrel far more to cover their depth.

I have a drawing I'll look out and post which may make things a bit clearer.

[Stagecoach]

Brian,

Here is the drawing I mentioned, it is specific to my Nikon 105mm but the same principle applies to your lens.

The drg shows the focus barrel serrations along with their rotation/no off to the marked focus distances on the X axis. The Y axis represents focus distance (camera to subject). You will see that the focus barrel angular/serrations travel is not linear with respect to focus distance, hence the curve.

This lens has a closest focusing distance of 0.314m (1:1) and I have scaled things just up to 3m focusing distance which is the last marking on the lens before infinity.

If we take a couple of examples at near and far subject distances we get ....................

Near : For a subject between 0.33m and 0.35m (20mm subject depth) from the camera we have 8 divisions and if we use 1/2 divisions it gives us 16 which at normal apertures is ample for stacking overlaps.

Far : For a subject between 1.0m and 1.5m (500mm subject depth) from the camera we have just 2.5 divisions and if we use 1/2 divisions it gives 5 which at normal apertures is ample for stacking overlaps.



So regarding the focus barrel rotation method we are able to use these equispaced serrations (angular movements) for both near and far subjects.

[JBW]

Brian, from the picture of those rocks my estimation is that the depth between the front of the nearest rock and the farthest greenery is about 2 m.

At 3.5 m (camera distance to the nearest rock) the DoF will be 0.85 m at f/14.

You would only be turning the focus barrel a small amount before the entire scene was OOF.

I set up a test with my lens, 105 mm (near enough the same for this). I focused on a point 3 m and on turning the focus barrel 3 'notches'/'grooves' a point at 5 m from the camera (plus all in front of it) was OOF.

The answer here is that at these long distances you need very few shots/intervals over a small depth such as this because of the large DoF. You could use 1/2 divisions.

When you come to shooting things small and much closer you will be able to rotate the lens barrel far more to cover their depth.

I have a drawing I'll look out and post which may make things a bit clearer.

I thought distance might be my enemy. Which means for ultimate sharpness i need to go over the entire sculpture with a proper overlap

[JBW]

Brian,

Here is the drawing I mentioned, it is specific to my Nikon 105mm but the same principle applies to your lens.

The drg shows the focus barrel serrations along with their rotation/no off to the marked focus distances on the X axis. The Y axis represents focus distance (camera to subject). You will see that the focus barrel angular/serrations travel is not linear with respect to focus distance, hence the curve.

This lens has a closest focusing distance of 0.314m (1:1) and I have scaled things just up to 3m focusing distance which is the last marking on the lens before infinity.

If we take a couple of examples at near and far subject distances we get ....................

Near : For a subject between 0.33m and 0.35m (20mm subject depth) from the camera we have 8 divisions and if we use 1/2 divisions it gives us 16 which at normal apertures is ample for stacking overlaps.

Far : For a subject between 1.0m and 1.5m (500mm subject depth) from the camera we have just 2.5 divisions and if we use 1/2 divisions it gives 5 which at normal apertures is ample for stacking overlaps.



So regarding the focus barrel rotation method we are able to use these equispaced serrations (angular movements) for both near and far subjects.

that does help.

[JohnRostron]

Thought that I would show you what my cardboard cut-out gizmo looked like:


The near ring, with the pointer, is fixed and the far ring, with the gradations, rotates with the focus barrel. This is fixed fairly firmly by an elastic band! I note the position on the dial of the near and far points and then interpolate, using one, two or three ticks on the outer dial, as appropriate.

John

[JBW]

Thought that I would show you what my cardboard cut-out gizmo looked like:


The near ring, with the pointer, is fixed and the far ring, with the gradations, rotates with the focus barrel. This is fixed fairly firmly by an elastic band! I note the position on the dial of the near and far points and then interpolate, using one, two or three ticks on the outer dial, as appropriate.

John

I like it.

[DanK]

I think Grahame's comments are spot on. Two or three images would have been sufficient, if you even needed more than one; the DOF calculator I used came up with a DOF of 0.9 m at a distance of 2.5m, using your camera.

I agree with him that you should focus manually, using the serrations on your focusing ring as an indicator of focus changes. Try the same shot with different amounts of change, and compare. Once you have done this a while with your equipment and a given distance range, it will become intuitite. I don't do stacking at a distance, but for table-top macro, I have done this so often that I don't even use the software I bought to control changes in focus. It's all intuitive now, and it will be in time for you as well.

Focusing using AF with points you select seems cumbersome and risky, since it requires that you either estimate distances accurately or take a huge number of superfluous photos.

[JBW]

I think Grahame's comments are spot on. Two or three images would have been sufficient, if you even needed more than one; the DOF calculator I used came up with a DOF of 0.9 m at a distance of 2.5m, using your camera.

I agree with him that you should focus manually, using the serrations on your focusing ring as an indicator of focus changes. Try the same shot with different amounts of change, and compare. Once you have done this a while with your equipment and a given distance range, it will become intuitite. I don't do stacking at a distance, but for table-top macro, I have done this so often that I don't even use the software I bought to control changes in focus. It's all intuitive now, and it will be in time for you as well.

That would be nice