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Stacking advice
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sat Jan 06, 2018 6:38 pm    Post subject: Stacking advice Reply with quote

I recently got an electronic rail and Im having some issues. The majority of the stack is smooth from one image to another then a random image will jump up just higher than the rest and then the next drop back down to where it started (if you get what I mean). Which makes a doubling up of hairs etc. and blurring detail. Ive tried moving the subject onto a different platform in case the shutter is causing some bounce but still happens.
Ive got a pretty sturdy set up and keep all vibrations to as low as possible so not sure why this happens each time. I never had this issue when using a manual rail.
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sat Jan 06, 2018 6:44 pm    Post subject: Reply with quote

Example

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mawyatt



Joined: 22 Aug 2013
Posts: 1593
Location: Clearwater

PostPosted: Sat Jan 06, 2018 7:01 pm    Post subject: Reply with quote

Could be your rail sticking (binding) then releasing (jumping).

What rail are you using and how is your setup configured?

I had some issues with Rail Wobble and used this technique to help reduce the effects.

https://www.photomacrography.net/forum/viewtopic.php?t=32361&highlight=axis+loading

Best,

Mike
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sat Jan 06, 2018 7:09 pm    Post subject: Reply with quote

I got a RS-90P from StackRail (https://www.stackrail.info/index.php/en/webshop/product/249-precision-focus-stacking-kit-sr-90p-usb-incl-shipping). Ive been using a 5 second hold time between movements and then a 4 second settle time. The rail itself is attached to a metal base and then on a sturdy bench with the helping hand holding the subject on a separate stand.
The images themselves arent blurred just random jumps in position.
The rail also makes quite a bit of noise when still, random screeching etc. I spoke to one of the sellers about it and they said its normal and wont effect image quality although I cant see how it wouldnt.
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mawyatt



Joined: 22 Aug 2013
Posts: 1593
Location: Clearwater

PostPosted: Sat Jan 06, 2018 7:51 pm    Post subject: Reply with quote

This is a good rail and may respond favorably to the reference I made above. As you can see in this thread the Off Axis Loading technique significantly improved the result for my situation and doesn't cost anything but a few rubber bands and a bolt/screw.

The noise is coming from the stepper motor and usually augmented by microstepping (stepping in fractions of the stepper motor minimum step angles).

Agree it's annoying, but probably not harming your images. You can still attempt to minimize it by selecting step sizes that don't require microstepping. The minimum step size you can make before using microstepping is thread pitch/# of steps per motor rotation (usually 200 to 400), while thread pitch for your rail is probably 1mm or 2mm, Stackshot rails are ~1.59mm (1/16"). Select your step size as integer increments of this minimum step value.

Best,

Mike
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sat Jan 06, 2018 7:58 pm    Post subject: Reply with quote

Thanks for the advice I'll give it a try
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19242
Location: Richland, Washington State, USA

PostPosted: Sat Jan 06, 2018 8:37 pm    Post subject: Reply with quote

I agree that the stacked image looks like it's suffering from some sort of doubling.

But that's unusual if the only problem is that the rail does a lateral shift once in a while. The reason is that stacking software normally aligns the frames based on image content.

There may be something unusual about this stack that is keeping the normal alignment process from working.

If this was stacked with the software that comes with the rail, then you might consider instead to download a trial of Zerene Stacker and run the same stack of images through that. The default settings for Align & Stack All (PMax) allow for all combinations of shift, rotate, and scale, which covers pretty much everything that can happen with this sort of setup. Then if you have residual problems you can use the techniques described at FAQs: How can I detect movement in my stack? to get a better handle on what's going wrong, at least at the level of the images.

--Rik
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sat Jan 06, 2018 9:00 pm    Post subject: Reply with quote

Thanks, this was stacked with Zerene and is one of around 8 stacks that have done the exact same thing. Thanks for the link I'll read it now.
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19242
Location: Richland, Washington State, USA

PostPosted: Sat Jan 06, 2018 9:05 pm    Post subject: Reply with quote

Sounds good. If you have trouble figuring out what's going wrong, write to support@zerenesystems.com for help. That's me too, just wearing a different hat. I may need to see the whole stack to figure it out.

--Rik
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sat Jan 06, 2018 9:16 pm    Post subject: Reply with quote

rjlittlefield wrote:
Sounds good. If you have trouble figuring out what's going wrong, write to support@zerenesystems.com for help. That's me too, just wearing a different hat. I may need to see the whole stack to figure it out.

--Rik


Thats great thank you. I'll continue to play and see if I can sort it but if not I'll get in touch. Much appreciated
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Deanimator



Joined: 23 Oct 2012
Posts: 593
Location: Rocky River, Ohio, U.S.A.

PostPosted: Sat Jan 06, 2018 10:10 pm    Post subject: Reply with quote

It probably wouldn't hurt to post one or more images of your equipment to eliminate any issues there.

When I was shooting with my camera on a tripod and my subjects on a table, it was a lost cause. And that was only at 1:1.

I've got everything on the table now, and my camera rig on sorbothane feet and I'm still having a certain amount of vibration issues using continuous lighting and slow shutter speeds.
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Chris S.
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Joined: 05 Apr 2009
Posts: 3038
Location: Ohio, USA

PostPosted: Sat Jan 06, 2018 11:41 pm    Post subject: Reply with quote

Mant01,

I think you have a couple of different issues going on: First, part of your rig is clearly moving during image acquisition; second, your stacking software is not correcting for this movement for some reason. Rik is helping you with the latter.

For the former, I agree with Mike that off-axis loading can solve this sort of problem, so long as you figure out what portion of your rig is moving, and apply an off-axis load to the correct part. (As said, by “load,” we just mean an added push or pull so that things don’t jiggle.) Manually jiggling the various parts of your rig, to see where movement can occur, may be vital for determining where to apply such a load.

An oft-overlooked source of jiggle is the camera mount. Many cameras have play between camera and lens—side to side, up and down, and rotational play. And perhaps your helping hands-based subject stage has a bit of jiggle available to it?

Of course, the presence of a degree of freedom won’t manifest as a problem on its own—there needs to be an energy input to get the rig to move along it. Here, that noise coming out of your stepper motor might well matter. Noise represents vibrational energy. To say this doesn’t matter is to overgeneralize. As hypothetical questions, how loud is the noise (in other words, how much energy is there)? What is its pitch? What are the resonant frequencies of elements of your rig? Depending on the answers, this sort of noise might perturb one person’s rig, but not another’s. It's not practical for most of us to answer all these questions. And since something is moving elements of your rig between images, and since this did not occur before you got your automated rail with its noisy motor, we have to consider the noisy motor a potential contributor to the problem.

Your description of this noise as "random" bothers me. A bit of constant whir or whine is understandable, if the motor is set for a high holding torque. (This said, I don’t happen to like it, and don't find high holding torque necessary for a horizontal rig.) But a stepper motor making random noises in an application like yours raises my eyebrows.

mawyatt wrote:
You can still attempt to minimize it by selecting step sizes that don't require microstepping.

This could potentially help if the controller is smart enough to think, "Oh, I don’t need microstepping for this increment, so I’ll not use it." But are the macro-photography controllers on the market this robustly-programmed? I doubt it. With a home-built controller, where all potential variables are exposed to the builder, sure.

Does this controller permit user adjustment of motor torque? Voltage? Current? Amount of delay between pulses to the stepper motor? If even one of these adjustments is available, you might be able to tweak it and get rid of the noise. (If so, ask how, before beating your head against the wall.)

If not, I’d be seriously tempted to return a stacking rail where the motor runs noisily and nothing can be done about it. If that noise is random, much more so.

--Chris S.

--corrected typos


Last edited by Chris S. on Sun Jan 07, 2018 10:51 pm; edited 1 time in total
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sun Jan 07, 2018 3:16 am    Post subject: Reply with quote

The rail makes all sorts of noises, from high pitch screeching, low droning to sounding like air escaping. It stops every time it takes a step forward and then the noise changes to something else. When I spoke with seller about potential vibrations from it he just said it's normal and it won't make a difference. I also messaged the manufacturer a couple days ago but haven't heard back yet. The rail does have a voltage setting for both active and when not in use but I left it on default. I'll try adjusting it to see if that makes a difference.
As far as micro stepping in the program it has a calculator where you put the details of what you are using and settings etc. then it recommends a step size.
Side note, I posted a different thread where it looks like I might be having a problem with triggers and flashes going off at slightly different times. I was wondering could this be a cause of doubling up? Like different areas being highlighted depending on when the flashes hit while the shutter is open? Probably not but just a thought.


Last edited by mant01 on Sun Jan 07, 2018 3:25 am; edited 2 times in total
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mant01



Joined: 10 Aug 2013
Posts: 111
Location: Durham, UK

PostPosted: Sun Jan 07, 2018 3:21 am    Post subject: Reply with quote

Deanimator wrote:
It probably wouldn't hurt to post one or more images of your equipment to eliminate any issues there.

When I was shooting with my camera on a tripod and my subjects on a table, it was a lost cause. And that was only at 1:1.

I've got everything on the table now, and my camera rig on sorbothane feet and I'm still having a certain amount of vibration issues using continuous lighting and slow shutter speeds.


With a manual rail I could do around 4.1 for about 100 image stack, anymore was pushing it (but with 2 flash units). I thought this was going to make my life easier lol I'll post an image of the rail set up later when I get the chance but really nothing much to look at. Just the rail on a metal sheet, on a heavy wooden bench.
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Lou Jost



Joined: 04 Sep 2015
Posts: 2710
Location: Ecuador

PostPosted: Sun Jan 07, 2018 7:21 am    Post subject: Reply with quote

Your flash triggering hypothesis is a good one. At very high m I have noticed that there is a ghost image from my master flash (a very small unit attached to the camera) and the slaves. I suppose this is caused by a time delay between master and slave. It can also happen that the master only triggers one of a pair of slave flashes, and that slave triggers the other slave. You'll have stronger ghosting then. Nowadays I put an aluminum foil shield between the master flash and subject, and I make sure both slaves are triggering from the master.
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