cbtsam Loc: Monkton, MD

I posted this in Close-Up Photography, and only got one response, so I'm trying it again here, with some extra questions.

I have read about two different tactics for collecting exposures for focus stacking. (I) In the first, the camera stays in one position, and the lens is focused on a different point in the subject for each exposure. (II) In the second, the lens focus doesn't change, but the camera is moved slightly closer or further for each exposure, so that each exposure still features a different focus point.

I use an AF Micro Nikkor 105mm f/2.8 D lens. Like many (all?) Micro Nikkors, the focal length actually changes as focus changes, particularly as one approaches 1:1, so the perspective changes as the focus changes. Similarly, as one moves the camera closer to the subject, the perspective shifts a bit. I assume that the stacking software takes all of this into account.

My first question is: What reasons (if any) are there to prefer tactic (I), with the stationary camera, over tactic (II), with the moving camera, or to prefer tactic (II) over tactic (I)?

This has become a more interesting question with the appearance of the D850, which provides an automated feature for tactic (I), but not for tactic (II).

A second question concerns the number of exposures to use. In general, does the process work better if I take more exposures at different focus points very close together, or fewer further apart?

A third question concerns the results I've gotten using Photoshop CC to combine images. While I generally do get sharp focus from front to back, I also get some edges that are not well-formed. Is this the limitation of the Photoshop algorithms, or something rather common in focus stacking? (I've gotten these edge problems with single flowers, using a combination of some twenty odd images.)

Finally, a fourth question concerns education recommendations. Obviously, I need some more education in this area.

Thanks in advance for your input; I'm looking forward to it.

Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga

Pose this question in the "True Macro" forum for the best answers...

Rongnongno Loc: FL

I can address only this part...

If you move the camera forward or backward the perspective changes with the focusing plane. I would not do that.

Now if the camera is moved side ways on the same focus plan this would create a stitch-able panorama. This type of motion is used for reproducing large documents (or not so large depending on the intent) or parallel (walking) panoramas. Be aware of parallax errors when doing this.

This may not be the answer you seek.

As to the D850... It is not able to move itself so... Only the first type, moving the focus plane is available.

Bobspez Loc: Southern NJ, USA

If you move the camera the images may not stack as they become different sizes.

LoneRangeFinder Loc: Left field

As Screaming Scott posted: you posted in the “wrong” forum.

Here’s some information on image size: https://zerenesystems.com/cms/stacker/docs/faqlist#does_zerene_stacker_correct_for_changes_in_magnification_as_i_focus

FWIW: Zerene is a software dedicated to focus stacking—and is still the best available.

The two methods are dependent on magnification: With macro, I would recommend a focusing rail; for landscapes, your only option is the focusing ring

Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga

IIRC there is some software that will compensate for that, but I seldom stack my macro images and I can't be certain. That's why I suggested posting the question over in the "True Macro" section as there are several people who do a lot of stacking.
EDIT: What limited stacking I do, I do use a focus rail

Rongnongno Loc: FL

Creating a stack for focus depends on several things:
- Lens used
- Distance to subject
- Set Depth of Field (DoF) of the lens
- Final Acceptable Field of Sharpness (AFoS) needed.

To select what lens is relatively simple. For macro use a macro lens by example.
Distance to subject is important as this will determine how deep the DoF will be at a set lens Aperture choice.
DoF is determined by the aperture choice as well as the lens used and the distance subject/lens.
The AFoS is created by the DoF, it is similar to it but different in a way that it is about surface vs length (simple explanation).

When creating a stack you need to know how the DoF is distributed. The generic 'acceptable' description is 1/3 in front, 2/3 in the back. Knowing this and using the 2/3 in the back you can calculate/predict the number of shots as well as the focusing plane location so that you cover the final AFoS.

Each lens, however good, creates a distortion on the sides. This is why you find some discrepancy there. It is is expected. This is the reason for using the center of a lens as a composition frame to obtain better results, the sides are simply cropped away.

Now my answer is not all that precise, I am aware of that. I hope other folks will pipe in and fill in the blanks and correct my inaccuracies if any.

By the way, this covers all stacking so specialized fields may need specialized settings that I am not aware of.

cbtsam Loc: Monkton, MD

Thanks, LoneRangeFinder: your website reference answered the first question about the two ways to focus very clearly and thoroughly, after I clicked on a link to another page (https://zerenesystems.com/cms/stacker/docs/troubleshooting/ringversusrail). It turns out that, for my purposes - single flower portraits - the focus ring seems like the best bet, which perhaps helps explain why my focus rail images didn't work out as well as I might have hoped. I'll look into Zerene, and I've read about another option to Photoshop as well. As for the "wrong" forum, I don't do "true macro" (1:1 or closer) so I thought the Close Up forum would be useful, but it didn't turn out that way. Anyway, thanks again.

LoneRangeFinder Loc: Left field

No worries. I just know that most stackers are in the macro section—and there are some FAQs there that also might help.

cbtsam Loc: Monkton, MD

Thanks Ron. After dabbling in photography for approximately 60 years, I am embarrassed to admit that I don't know how to calculate depth of field. Your note, however, jogged my memory, and I recalled that I have an app on my phone that does it for me! It's called Digital Depth of Field. Turns out that at the sorts of distances I typically work with, the depth of field at f/11 (my typical aperture) is about 0.7 inches, and is distributed about 49% in front & 51% behind the point of focus. Now if only the lens showed focus distance that accurately! Anyway, thanks for your help.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

The preferred method is to move the camera for stacking, if doing macro. Of course this is predicated on the ability of the amount of movement fore/aft is able to be handled by the rail you are using. By this I mean if your subject is 5 inches in depth and you are using a rail that only has 4 inches of total movement, you are not going to get the result you are looking for.

The reason it is preferred to focusing is exactly what you describe - the change in focal length and the corresponding change in field of view as you focus closer to 1:1. Nikkor lenses are not as bad as some third party lenses. Moving the camera/lens addresses this as long as the rail is long enough.

The change in perspective at macro distances is not an issue since only the subject is in focus and the background is of no real concern. The greater concern is the increase in depth of field when you focus adjust. When you distance-adjust the DoF is constant, you are just moving it.

In the beginning I used to use a DoF app on my phone, and determined the DoF for my focus distance and aperture. I would cut the distance in half for more accurate focus. So if the calculator said at F11 at a given distance I would have 1 in DoF, I would use .5 in. I would use a rail and advance the focus 3/8" to ensure no gaps. What I do now is just "wing it" with focus adjusting, making sure I use very tiny increments on the focus ring. Any perspective/magnification/angle of view issues are typically handled well by software. If your lens is a heavy breather, make sure that you use a looser composition, since much of the border of your image will be unusable.

It is better to have more shots and overlap your focus as much as possible, to avoid gaps in focus, regardless of whether you focus-adjust or distance adjust to create your stack sequence.

When doing stacking for more distant subjects, like architectural and landscape, there is only one real option - to change focus, but "breathing" is not an issue at those distances.

Hope this provides some clarity.

.

joseph premanandan

in my opinion focus stacking is a more advanced version of hyperfocal distance which is rather subjective.focus stacking makes the foreground,the middle ground and the background in full focus and is a good option for landscape photography

TheDman Loc: USA

Focus stacking ignores hyperfocal distance. It's often a better way of accomplishing what hyperfocal tries to do.

cactuspic Loc: Dallas, TX

Both methods will work; but, depending on the magnification, one will work better. For magnifications of 1:1 or less, turning the focus ring tends to work better. For magnifications greater than 1:1, a rail works better. If you go to the Zerene Stacker website, there is a tutorial on this very topic by the author of Zerene.

In addition to the true macro forum, the website photomacrography.net is a wealth of info. Enjoy stacking although it can become addictive.

peterg Loc: Santa Rosa, CA

Perhaps. But if moving the camera didn't work, people wouldn't be using focusing rails. Example: "StackShot" by Cognisys, http://www.cognisys-inc.com/products/stackshot/stackshot.php .