jackm1943 Loc: Omaha, Nebraska

I frequently do focus stacks at around 10X with between 100-200 images using my WeMacro focusing rail. It's not unusual to end up with one or more bright worms from hot pixels. I expect the worms to be in a fairly straight line but sometimes the lines are not straight at all. Does that mean that something in my system was not stabile and was moving around? That's my assumption but I'm hoping someone here with more experience can confirm whether that's the cause. I thought that I had a very stabile system free of movement but now am not sure.

rgrenaderphoto Loc: Hollywood, CA

Not in your system, but probably in whatever you were focusing on. Is it an issue that cannot be resolved with a bit of post-processing with a healing tool in Lightroom or Photoshop?

jackm1943 Loc: Omaha, Nebraska

Thanks rgrenaderphoto. I hadn't really considered that so much but now that you mention it, I think that could be likely. At 10X, just a few microns movement could account for that. It's not fixable in PP because it can result in areas out of focus and/or the program (Zerene) may not be able to correct for it. The last time I saw it I was photo stacking a leaf. Organic materials could possibly wilt or dry out enough to move a few microns during the half-hour or so it takes to take all the photos. I'm going to try photographing something that I know is rock solid and see if the worms are straighter.
JackM

rgrenaderphoto Loc: Hollywood, CA

½ hour? Why so long?

Wallen Loc: Middle Earth

Not knowing your setup, this are from my own experience with my own tools;

Hot pixels? If the hot pixel appears in the same spot, then there is a problem in the sensor. If the problem is not too severe, shortening the exposure time and rest in between shots may help.

Understand the depth of field of the chosen settings. Micron adjustments and hundreds of exposure may be an overkill. Instead of embracing complications, I aim to simplify as much as possible. Less photos, less complications, less problems to occur.

If the cause is a pinpoint bright spot/spectacular highlight, then I consider a controllable source of luminance matched to a better light box/diffuser. Sometimes i would match the diffuser to the need of the item. I also do test shots and chimp a lot.

Is the subject itself a problem? Jewelry and reflective stuffs are notorious for bright unwanted spots. Changing light source location may help.

As for the bright spot forming a worm, are you using a lens or camera with vr? The shifting mechanism in the lens may be shifting the light spot. How steady is your tripod? how heavy is your hand when you do the adjustments? is the floor stable? Is there no wind? The camera holder may be stable but what about the lights?
You would know the tools and situation much more than we can imagine. Keep asking yourself possible causes and cross each out after a test of probable cause to precisely address the problem.

jackm1943 Loc: Omaha, Nebraska

Well, if you need 350 shots at 5 micron increments, about 5 seconds between shots, add it up. That doesn't include actual shutter time. Most sessions don't require that many shots but seldom less than 100 at 10X.
JackM

jackm1943 Loc: Omaha, Nebraska

Thanks Wallen. The bright worms are really not the problem, I seldom get more than one or two of them and they are easily fixed. The issue for me is that I think the worms should be straight line and not crooked. To me, crooked means something moved. I don't make any adjustments while the WeMacro is working. Everything is on a concrete basement floor in my former darkroom, no air movement. The WeMacro is mounted on a heavy Bogen 3033 tripod with a geared head. Once the WeMacro starts, I usually leave and watch TV until it beeps that it's done. I'm allowing at least 220 microns for backlash so the first 50 or so pictures aren't even fed into Zerene. What set off this rant for me was photographing small spots on a dried leaf and I'm now thinking it's more likely that the leaf itself was moving a little. And, I'm not certain I trust the geared head to hold completely still either. I'm going to do a few more tests photographing something I know is dead solid to try to confirm this. I obviously have more work to do.
Thanks again, JackM

sippyjug104 Loc: Missouri

"Birds of a feather, flock together." Of course, I experience the same "hot pixel" worm trails. The reason the worms are not straight lines is due to the camera advancing as the method used for stacking.

When using a method of a stationary camera and subject and changing the focus of the lens, you would see a different hot pixel worm trail signature. Cameras with built-in focus stacking or using a Helicon focus tube would be examples of the difference between the two.

Sometimes I do deep stacks at 10X+ and a type of "smeared banding" may occur on a horizontal and vertical edge. When I go overly deep, that banding starts straight and then takes off at an angle.

I use the same WeMacro rail as yours and I am on a concrete eight-foot depth concrete floor. I have a 300+ pound lab cabinet with a one-inch thick acid-proof top which is why it is so heavy. It is set on high-density isomode vibration mounting pads that we used in setting equipment. Setting on the top is a 75+ pound one-inch thick granite slab which is also set on isomode pads. The WeMacro horizontal/vertical mounting base has vibration isolation and I have it glued to the granite slab. The WeMacro Rail is firmly attached to its base. The subject stage platform is also attached to WeMacro base so that if there is any vibration, the camera and the subject move together so the line of sight cannot weaver. AND....I get the same worm trails that you do.

jackm1943 Loc: Omaha, Nebraska

Thanks Sippyjug. When I do get "straight" worms, they are always aimed toward the center of the final image, which is what I would expect. Sometimes they turn around and head off in another direction, then I'm certain something is not holding still or moving correctly. I currently have two basic methods and am not certain which is better. First is having my rail and camera on a heavy tripod next to a heavy metal desk holding the subject. The second is having the rail and camera on a platypod on the heavy table along with the subject. I have either a geared head or large ball head to choose from. I prefer the geared head because it is easier to set up but I don't think it's as steady as the ball head. I'm using a mirrorless camera and electronic shutter to further eliminate shaking.

I also occaissionally see the smeared banding you described, usually on the top and/or the left side of the final image. I don't know what causes it but I simply crop it out.

I used to enjoy large format photography and wet darkroom because of all the "fiddling" around involved. I am pleasantly finding extreme macro to be just as mentally challenging and a lot less physically challenging. 😎
JackM

bwana Loc: Bergen, Alberta, Canada

Quite a few modern cameras have hot pixel 'fix' tools. Try using it if your camera has this feature.

bwa

jackm1943 Loc: Omaha, Nebraska

[quote=bwana]Quite a few modern cameras have hot pixel 'fix' tools. Try using it if your camera has this feature.

bwa[/quote

Thanks bwana, I'll check that out. Actually, I always hope to find at least one hot pixel worm on focus stacks because it tells me something about how stabile my system is. They are very simple to correct.
JackM

Robertl594 Loc: Bloomfield Hills, Michigan and Nantucket

Gary,
I attend various workshops. The one I’m most interested in currently is macro. Your work is the best I’ve seen and you have been so generous with your time and assistance.

Would you consider putting on a workshop for interested folks? I’m sure there are quite a few of us who would be willing to pay.

Hope I’m not overstepping.
Best
RL