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Stacking advice
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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Sun Jan 07, 2018 7:27 am    Post subject: Reply with quote

mant01 wrote:
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.


I have 8 stepper motor driven rails I've collected over time (long time), Stackshot, WeMacro, THK and MJKZZ (Your RS-90), some have 200 and some 400 steps per rotation motors. They all make noise in varying degrees, from high pitched "whines" while stationary to "groaning" while moving. The high pitched whines didn't bother me much as I could barely hear them, but my wife sure could Embarassed

The THK KR20 modified rails are the loudest, with a very loud "groan" when moving forward or backwards. They really get loud if you increase the rail speed under the Stackshot controller, and I do mean LOUD Shocked

As Chris mentioned, if you can hear it somethings moving. This was concerning to me long ago as I brought this very subject up on a thread somewhere. Rik indicated he had been concerned as well but found no image degradation due to the motor noise/whine, which occurred while stationary. I had found the same, but still bothered by the fact that something IS moving! So I set out to minimize the noise and realized that the stepper motors use multiple windings energized at different times to create the microstepping capability. Since the magnetic cogs in the motor are positioned such that the rotor naturally rests being magnetically held in place without any additional electromagnet influence it seemed that when energized this would require less winding current to "hold" the rotor in place. While with microstepping the rotor must be held between cogs electromagnetically, thus more winding current required and thus more possible noise from the winding current inducement. So positioning the rotor such that it didn't have to straddle the magnetic cogs should require less winding current and thus produce less noise. This proved true will all my rails and stepper motors, some more than others...and worked with the Stackshot and WeMacro controllers. This didn't eliminate the noise but did reduce it some, so now I try and position my stacking steps such that they are integer steps of the stepper motor/rail thread pitch minimum. I haven't seen any degrading image effects from this noise, nor microstepping vs. not, but it just seemed a better engineered solution to me. Being an engineer/scientist I'm always looking for a better engineered solution, if I can afford it Rolling Eyes

Your setup can act as a sounding board as well, so you might be able to reduce the noise intensity by looking here.

A simple test you can perform to evaluate IF the noise is causing image degradation is take an image at high magnifications with the motor engaged and retake the same image with the motor disengaged. After comparing these images you can decide if the noise is causing degradation. In my case it didn't.

Anyway, hopefully you don't have to replace your motor or rail.

Best,

Mike
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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Sun Jan 07, 2018 8:06 am    Post subject: Reply with quote

Lou Jost wrote:
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.


Lou,

There must be a delay between the master and slave, hopefully only a small one though. I would think that the newer RF devices would be quicker since they operate at 2.4GHz with much higher data rates.

I found that using the cheap 433MHz old RF triggers simultaneously with Optical (S1) slave gave a more uniform overall flash result.

Some of the better RF systems and speedlights/strobes have a built in delay function to help align multiple instances of such, this might help with ghosting issues. I'm fooling with that feature now to try an enable EFCS with flash and in Live View with the Nikon D850 and D500. Basically trigger the camera and strobe simultaneously, but delay the actual optical flash to account for the camera trigger to shutter opening delay (~145ms for the D850).

Best,

Mike
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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Sun Jan 07, 2018 8:36 am    Post subject: Reply with quote

mant01 wrote:
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.
Quote:
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.


Following up on this with Lou's note.

The older 433MHz triggers surely were designed such that the "channel" trigger code was sent out (transmitted) more than once, maybe even 3 or 4 times. This makes sense because it would cost nothing additional to do so, and the design would be considered "more robust" since it would have a higher "hit rate" to advertise with less misfires!

Assuming this is true, then it's highly likely with a multiple flash/strobe setup, that one flash device could decode the "trigger" command first while another flash device could decode correctly on a later repeat of the code, maybe towards the end of the transmission. Since the code data rate is low, the actual time between the proper decodes from each flash device could be considerable, maybe many milliseconds. Under normal use this would go unnoticed, but upon close examination might be such that this is the source of doubling/ghosting in the images.

This is pure speculation regarding the RF Triggers behavior and not backed up with measurements (if I had a scope could be though), so please don't jump all over me Chris Very Happy

Cheers,

Mike
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Lou Jost



Joined: 04 Sep 2015
Posts: 1971
Location: Ecuador

PostPosted: Sun Jan 07, 2018 9:16 am    Post subject: Reply with quote

Mike, thanks for the in-depth information. I had seen this ghosting with optical (not RF) master-slave flashes, and thought it might be due to delays between flashes, and when I made sure both slave flashes received the signal at the same time, and made sure to block the master flash from the subject, the ghosting disappeared. Could be coincidence I suppose, but I don't think so. It happened more than once.
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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Sun Jan 07, 2018 9:27 am    Post subject: Reply with quote

Lou Jost wrote:
Mike, thanks for the in-depth information. I had seen this ghosting with optical (not RF) master-slave flashes, and thought it might be due to delays between flashes, and when I made sure both slave flashes received the signal at the same time, and made sure to block the master flash from the subject, the ghosting disappeared. Could be coincidence I suppose, but I don't think so. It happened more than once.


Lou,

Think you are absolutely correct. The Master must flash and the Slave must sense the flash and then trigger itself to flash. This must take some time to happen and separate the two, or more, in time for the optical flash pulses. By blocking the Master optical pulse, you've effectively removed the delay!

Best,

Mike
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mant01



Joined: 10 Aug 2013
Posts: 106
Location: Durham, UK

PostPosted: Sun Jan 07, 2018 9:53 am    Post subject: Reply with quote

Thank you everyone for the help and information it's interesting stuff and much appreciated.
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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Sun Jan 07, 2018 1:41 pm    Post subject: Reply with quote

Just did a quick test with the THK rail and Stackshot controller. I seem to get more noise when moving or stepping with the High Precision Threshold parameter set Lower rather than Higher. So it seems this parameter is controlling the waveforms and timing such that Higher setting is better for rail noise when moving. While playing around I did get the dreaded "whining" sound at one stationary location, but can't seem to reproduce it!! Murphy again, when I want this noise I can't get it, but when I do a stack and leave the rail energized it will show up, especially if my wife around Rolling Eyes

Anyway, its the stationary noise that may affect images and that doesn't seem to be influenced by this High Precision Threshold parameter, but the noise produced while moving does, lower noise with a Higher Threshold setting.

Best,

Mike
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 18504
Location: Richland, Washington State, USA

PostPosted: Sun Jan 07, 2018 3:02 pm    Post subject: Reply with quote

mawyatt wrote:
While playing around I did get the dreaded "whining" sound at one stationary location, but can't seem to reproduce it!!

As I remember my experiments from long ago, the whining sound was completely repeatable but very different from one microstep position to another. To reproduce the problem, I suggest to set your nominal step size to be one microstep, then slowly run a series of steps. The sound should repeat every 16 microsteps, or maybe every 32 or 64 microsteps depending on exactly what hardware is being used. (64 microsteps will be 4 full steps, which should get back to driving the same coils with the same polarity.)

--Rik
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mant01



Joined: 10 Aug 2013
Posts: 106
Location: Durham, UK

PostPosted: Mon Jan 08, 2018 12:04 pm    Post subject: Reply with quote

I've done some tests and I'm happy to say that things have improved. Reducing the voltage whilst active has had a massive reduction in the noise the rail produces. Also I noticed that one of the flashes wasn't consistently creating the same output of light. When checking those images it seems to be the cause of creating the doubling of the hairs. Once I removed those the issue stopped. Ive included a stack I did today to test out the changes. Please excuse the bad lighting.
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rjlittlefield
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PostPosted: Mon Jan 08, 2018 12:32 pm    Post subject: Reply with quote

Looks better.

The broad halos in background, especially visible at upper left, are a typical artifact of PMax. For this sort of subject, a very effective way to kill those is to retouch from a DMap output image that was made with a contrast selection threshold set to make all the background be "black in preview", except for a very narrow rim around the subject. For this image, a setting around 40% looks about right, but you can tell better when looking at the full resolution stack. The goal is to cover any odd blotches with black, so that all of the background that does show, is natural color.

--Rik
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mant01



Joined: 10 Aug 2013
Posts: 106
Location: Durham, UK

PostPosted: Mon Jan 08, 2018 12:44 pm    Post subject: Reply with quote

rjlittlefield wrote:
Looks better.

The broad halos in background, especially visible at upper left, are a typical artifact of PMax. For this sort of subject, a very effective way to kill those is to retouch from a DMap output image that was made with a contrast selection threshold set to make all the background be "black in preview", except for a very narrow rim around the subject. For this image, a setting around 40% looks about right, but you can tell better when looking at the full resolution stack. The goal is to cover any odd blotches with black, so that all of the background that does show, is natural color.

--Rik


Thank you I'll give that a try. Also a big thank you to everyone for all the help. Having so many helpful knowledgeable people is a godsend for a non-technical happy snapper like me.
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mant01



Joined: 10 Aug 2013
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Location: Durham, UK

PostPosted: Mon Jan 08, 2018 2:01 pm    Post subject: Reply with quote

Thanks that did help smooth it Very Happy

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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Mon Jan 08, 2018 2:24 pm    Post subject: Reply with quote

mant01 wrote:
I've done some tests and I'm happy to say that things have improved. Reducing the voltage whilst active has had a massive reduction in the noise the rail produces.
Quote:
Also I noticed that one of the flashes wasn't consistently creating the same output of light.
When checking those images it seems to be the cause of creating the doubling of the hairs. Once I removed those the issue stopped. Ive included a stack I did today to test out the changes. Please excuse the bad lighting.


Nice image, looks like you've got things well under control. Suspect most have had issues with non-uniform light outputs from speed lights and strobes, I know I certainly have Rolling Eyes So don't feel alone Very Happy

Best,

Mike
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mant01



Joined: 10 Aug 2013
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Location: Durham, UK

PostPosted: Mon Jan 08, 2018 3:53 pm    Post subject: Reply with quote

Lol thank you and thanks for all your help
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mawyatt



Joined: 22 Aug 2013
Posts: 1199
Location: Clearwater

PostPosted: Mon Jan 08, 2018 8:19 pm    Post subject: Reply with quote

mant01 wrote:
Lol thank you and thanks for all your help


You are welcome. BTW I've had my best luck with the Adorama Studio 300 AC Strobes (Godox SK300II), they have a consistency spec of 2%.

Best,

Mike
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