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Need help with strobes.
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Wed Jan 03, 2018 3:12 pm    Post subject: Reply with quote

Ted,

I'm not saying Yonguno is bad, just not what I needed for stacking. Missing a trigger now and then probably isn't a big deal for most folks in normal use, but ruining a long stacking session wasn't acceptable. This happened too many times and that starting me searching a number of years ago. I'm sure some of the more expensive RF triggers are fine, but not within my budget, so I selected Godox (Adorama).

I don't think having a really fast shutter speed is that important for vibration control IF you are using flash. Most speedlights and modern studio strobes (like your 300) are pretty fast (some speedlights may need to be less that full power) and essentially create the exposure regardless of shutter period (assuming the flash occurs within this period). IF you ARE NOT using flash then the shutter period is important and usually faster is better, but also much slower can help where the vibrations are averaged over the long shutter period.

Experimenting is a good way to find out how your system behaves regarding vibration sensitivity and what shutter speeds are acceptable. Of course nothing is better than attempting to reduce the sources of vibration and their effects. Interestingly the camera body can be a major source and why I'm interested in getting the EFCS on the D850 working in Live View. Shutter curtains and mirror flop are major in camera vibration sources and the lens mechanism can augment this if it has a long mechanical time constant (think cantilever beam with the long lens).

So there are lots of things to consider when getting your setup tuned up for vibration reduction/isolation. Many folks here can give you lots of guidance in this area.

Best,

Mike
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Wed Jan 03, 2018 3:20 pm    Post subject: Reply with quote

mawyatt wrote:
Ted,

I found long ago that the Yonguno RF systems were not reliable for serious long stacking sessions, same goes for Neewer systems. Like you I would experience a few blank images, usually discovered only after or during a long stacking session with Zerene (Murphy's Law).

I did lots of investigation and decided that the Godox RF system was the best solution at the time, which has proven out to be the correct decision. Only issues I've had with the Godox/Adorama RF system is when the batteries get low in the R2 it can drop a trigger flash command. This, among other reasons is why I've been telling folks about these Godox/Adorama inexpensive & reliable strobe systems. Their RF system is fully compatible with their speedlights too!!

I'm shooting a tiny 1mm InP chip (D850 EFCS with LV) at 20X @ 2.5 micron steps with 300 images right now using this RF system.

Best,

Mike


Well my first session was ruined not because of the RF trigger missing a beat, but because I got a USB hiccup from the Stackshot controller to my Mac running Zerene. Zerene didn't like that and aborted the stack almost at the end (Murphy again!!). So I restarted another run and it completed, and I ran another with different lighting and it ran. So all in all ~900 images without a single RF missed trigger with Adorama R2 system!!

Best,

Mike
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Chris S.
Site Admin


Joined: 05 Apr 2009
Posts: 2888
Location: Ohio, USA

PostPosted: Wed Jan 03, 2018 10:44 pm    Post subject: Reply with quote

tevans9129 wrote:
I noticed on my D810 using a Nikon SB700 or a Yongnuo YN685 with the YN622 trigger system that my ISO was automatically set on 1250. Apparently that was a limit of some sort as the recorded ISO was less than that.

IOW, it is best to keep the SS below the HSS parameter when trying to minimize vibration, is that correct?

Ted,

For studio macro, I would turn off HSS entirely. So far as I can think of, HSS is the tool of choice only in one specific situation: When you are mixing flash with sunlight, and must use a shutter speed higher than the camera's maximum sync speed, HSS may make sense. In all other situations that come to mind, HSS is better turned off, as it has considerable downsides compared with regular flash mode.

As an aside, if your camera or flash are doing things with ISO--or any other adjustment--that are not transparent and understandable to you, this is not a good thing. For studio macro, I'd recommend setting both camera and flash to manual exposure and adjusting everything yourself.

When using flash to minimize vibration control, I'd suggest an approach as follows:
    1) Set your camera to base ISO. Set its shutter speed to 1/160 second (1/250 is often OK, but 1/160 is more forgiving of synchronization errors). Set your lens' aperture for best combination of sharpness and depth of field. (If you're using a lens without an iris, such as a microscope objective, the aperture is fixed.)

    2) Making sure that your flash units are turned off, take a picture of your subject. It should be completely black. If there is any image formation, you need to lower your room light so that it doesn't contaminate your flash images.

    3) Turn your flash units on, set them to manual, and set up whatever triggers you use. Adjust flash intensity by taking pictures and examining the histogram (apply the ETTR method). When this is done, you're ready to make your image.
--Chris S.
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tevans9129



Joined: 30 Nov 2017
Posts: 99
Location: TN

PostPosted: Thu Jan 04, 2018 7:40 am    Post subject: Reply with quote

Chris S. wrote:

For studio macro, I would turn off HSS entirely. So far as I can think of, HSS is the tool of choice only in one specific situation: When you are mixing flash with sunlight, and must use a shutter speed higher than the camera's maximum sync speed, HSS may make sense. In all other situations that come to mind, HSS is better turned off, as it has considerable downsides compared with regular flash mode.


When shooting birds and using flash as a fill, I set the aperture and SS that I want for the shot. It may be 1/1600 and F/5.6 and the ISO is auto, whatever is needed. For macro shots, I use Controlmynikon software and manual mode is selected for all settings.

Chris S. wrote:

As an aside, if your camera or flash are doing things with ISO--or any other adjustment--that are not transparent and understandable to you, this is not a good thing. For studio macro, I'd recommend setting both camera and flash to manual exposure and adjusting everything yourself.

I do.

Chris S. wrote:

When using flash to minimize vibration control, I'd suggest an approach as follows:[list]

1) Set your camera to base ISO. Set its shutter speed to 1/160 second (1/250 is often OK, but 1/160 is more forgiving of synchronization errors). Set your lens' aperture for best combination of sharpness and depth of field. (If you're using a lens without an iris, such as a microscope objective, the aperture is fixed.)


This worked fine when I was using speedlights as they were set at 1/64 or even 1/128. Primarily for fast recovery and less demand on the batteries. However, the Studio 300’s can only be set as low as 1/16 which required 500 plus SS for proper exposure as ISO 100 is my base. I know more diffusion is needed and I am working on that.
This is using an objective lens attached to a PB6 bellows so setting the aperture is not an option.

Chris S. wrote:

2) Making sure that your flash units are turned off, take a picture of your subject. It should be completely black. If there is any image formation, you need to lower your room light so that it doesn't contaminate your flash images.


It is, totally black.

Chris S. wrote:
3) Turn your flash units on, set them to manual, and set up whatever triggers you use. Adjust flash intensity by taking pictures and examining the histogram (apply the ETTR method). When this is done, you're ready to make your image.


That method worked with speedlights but not with the strobes so my thinking is there must be more diffusion or is there another option that I am not aware of?

I really appreciate you taking the time to offer suggestions and explanations, it is a long learning process for me, unfortunately.
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Thu Jan 04, 2018 7:54 am    Post subject: Reply with quote

Ted,

I usually use ~1/2" thick shipping foam diffuser over the strobe and a styrofoam cup over the subject. This causes enough diffusion and light loss I am usually at ~1/8 power with 4 studio 300 strobes.

Since the closest subject diffuser is the effective diffuser for your subject, you can simply move the strobes back or forward to also help control light. I usually have strobes ~18 inches from subject.

Remember these are 300WS output strobes, while your speed lights are 60~80WS, but you will find that you will need the extra for subjects requiring heavy diffusion, especially at high magnifications.

Best,

Mike
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tevans9129



Joined: 30 Nov 2017
Posts: 99
Location: TN

PostPosted: Thu Jan 04, 2018 8:57 am    Post subject: Reply with quote

mawyatt wrote:
Ted,

I usually use ~1/2" thick shipping foam diffuser over the strobe and a styrofoam cup over the subject. This causes enough diffusion and light loss I am usually at ~1/8 power with 4 studio 300 strobes.

Since the closest subject diffuser is the effective diffuser for your subject, you can simply move the strobes back or forward to also help control light. I usually have strobes ~18 inches from subject.

Remember these are 300WS output strobes, while your speed lights are 60~80WS, but you will find that you will need the extra for subjects requiring heavy diffusion, especially at high magnifications.

Best,

Mike


Thanks Mike, I will try to locate some 1/2" foam.
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Thu Jan 04, 2018 9:34 am    Post subject: Reply with quote

tevans9129 wrote:
mawyatt wrote:
Ted,

I usually use ~1/2" thick shipping foam diffuser over the strobe and a styrofoam cup over the subject. This causes enough diffusion and light loss I am usually at ~1/8 power with 4 studio 300 strobes.

Since the closest subject diffuser is the effective diffuser for your subject, you can simply move the strobes back or forward to also help control light. I usually have strobes ~18 inches from subject.

Remember these are 300WS output strobes, while your speed lights are 60~80WS, but you will find that you will need the extra for subjects requiring heavy diffusion, especially at high magnifications.

Best,

Mike


Thanks Mike, I will try to locate some 1/2" foam.


The Dollar Store has some large white foam core sheets that I use for reflectors, it's pretty dense and will provide considerable attenuation. The stuff I use for the strobe came with a package as shipping, it's a little thicker but more of an open foam thus less attenuating than the Dollar Store foam core sheets.

Best,

Mike


Last edited by mawyatt on Thu Jan 04, 2018 1:55 pm; edited 1 time in total
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Chris S.
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Joined: 05 Apr 2009
Posts: 2888
Location: Ohio, USA

PostPosted: Fri Jan 05, 2018 12:02 am    Post subject: Reply with quote

Quick note: I've split some responses off into a new thread, ISO invariance, ETTL, and Uni-WB, so that we can discuss these issues without taking tevans9129's questions about strobes off-topic.

tevans9129 wrote:
This worked fine when I was using speedlights as they were set at 1/64 or even 1/128. Primarily for fast recovery and less demand on the batteries. However, the Studio 300’s can only be set as low as 1/16 which required 500 plus SS for proper exposure as ISO 100 is my base. I know more diffusion is needed and I am working on that.

(snip)

That method worked with speedlights but not with the strobes so my thinking is there must be more diffusion or is there another option that I am not aware of?

Got it. Your studio strobes are too bright even at 1/16, and do not have a greater reduction setting. You have found a work-around in using high-speed-shutter mode and a 1/500 second shutter speed. There are indeed other options that will serve you better in the long run.

Let's discuss why your workaround has worked. In HSS mode, a flash tries to mimic a continuous light source. It either fires many times repeatedly, or as Mike pointed out with some units, greatly elongates the flash duration. In order to accomplish either of these things without burning up or running out of energy, the flash needs to reduce its output intensity. So in standard mode, a flash gives one really bright, brief pop; in HSS mode, it gives a much dimmer, longer pop, or set of pops. On the camera side of things, with HSS, you set your shutter speed more as you would for continuous light. With normal flash, shutter speed does not affect exposure, as the flash duration is much shorter than shutter speed. But with flash in HSS mode, as with continuous light, shutter speed does affect the amount of light that gets through the shutter.

With your workaround, you are using the strobe's self-dimming in HSS mode to attenuate the light so that you don't burn out the image. I'd recommend avoiding this approach, as it combines the downsides of both flash and continuous light, without the benefits of either. (If you'd like a longer explanation, say the word.)

The fortunate thing is that attenuating flash is rather easy. As you've mentioned, you can add diffusion (and, as you know, you're likely to want more diffusion anyway). Or you can move the flash farther from the subject (doubling the distance will quarter the light). You can bounce the light off something white, instead of shining it on directly the subject directly (huge reduction, and often a nice alternative to diffusion). Or you can simply block a portion of the light (for quick flash adjustments in the field, I often place my hand over part of my flash--much quicker than turning a dial).

Does any of this help?

tevans9129 wrote:
. . . it is a long learning process for me, unfortunately.

We've all been in your shoes. Fear not, it will eventually "click" for you! It has for us all. Very Happy

--Chris S.
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tevans9129



Joined: 30 Nov 2017
Posts: 99
Location: TN

PostPosted: Fri Jan 05, 2018 7:57 am    Post subject: Reply with quote

Chris S. wrote:
Quick note: I've split some responses off into a new thread, ISO invariance, ETTL, and Uni-WB, so that we can discuss these issues without taking tevans9129's questions about strobes off-topic.

tevans9129 wrote:
This worked fine when I was using speedlights as they were set at 1/64 or even 1/128. Primarily for fast recovery and less demand on the batteries. However, the Studio 300’s can only be set as low as 1/16 which required 500 plus SS for proper exposure as ISO 100 is my base. I know more diffusion is needed and I am working on that.

(snip)

That method worked with speedlights but not with the strobes so my thinking is there must be more diffusion or is there another option that I am not aware of?

Got it. Your studio strobes are too bright even at 1/16, and do not have a greater reduction setting. You have found a work-around in using high-speed-shutter mode and a 1/500 second shutter speed. There are indeed other options that will serve you better in the long run.

Let's discuss why your workaround has worked. In HSS mode, a flash tries to mimic a continuous light source. It either fires many times repeatedly, or as Mike pointed out with some units, greatly elongates the flash duration. In order to accomplish either of these things without burning up or running out of energy, the flash needs to reduce its output intensity. So in standard mode, a flash gives one really bright, brief pop; in HSS mode, it gives a much dimmer, longer pop, or set of pops. On the camera side of things, with HSS, you set your shutter speed more as you would for continuous light. With normal flash, shutter speed does not affect exposure, as the flash duration is much shorter than shutter speed. But with flash in HSS mode, as with continuous light, shutter speed does affect the amount of light that gets through the shutter.

With your workaround, you are using the strobe's self-dimming in HSS mode to attenuate the light so that you don't burn out the image. I'd recommend avoiding this approach, as it combines the downsides of both flash and continuous light, without the benefits of either. (If you'd like a longer explanation, say the word.)

The fortunate thing is that attenuating flash is rather easy. As you've mentioned, you can add diffusion (and, as you know, you're likely to want more diffusion anyway). Or you can move the flash farther from the subject (doubling the distance will quarter the light). You can bounce the light off something white, instead of shining it on directly the subject directly (huge reduction, and often a nice alternative to diffusion). Or you can simply block a portion of the light (for quick flash adjustments in the field, I often place my hand over part of my flash--much quicker than turning a dial).

Does any of this help?

tevans9129 wrote:
. . . it is a long learning process for me, unfortunately.

We've all been in your shoes. Fear not, it will eventually "click" for you! It has for us all. Very Happy

--Chris S.


Yes, it does help enormously. It is just that I am a slow learner....but I make up for that by forgetting very quickly.

Two positive developments in my journey, I am learning more about diffusion material and I received the Xpro trigger yesterday and found that I can use it to adjust the levels of the strobes, at least down to 1/128, I have not tried or had the need to go beyond 128. I ran a stack last evening at 1/30 and ISO 100 with one strobe on 1/16 and the other one on 1/64 with nothing more than a styrofoam cup for diffusion. I was using more extension than I had been using so more light was needed.

I think now the challenge is the placement of lights and learning where the best results are located. This I hope to learn by looking at the images of others and reading the excellent knowledge base of those in this group, it is much appreciated. It really helps us trying to learn when all of the technical data is provided by those posting images.

Your suggestions and advice is always welcome and appreciated.
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Fri Jan 05, 2018 9:05 am    Post subject: Reply with quote

Ted,

I don't think you can get these strobes to go below 1/16 power. I know this for sure with the R2 triggers and from the rear controls on the strobes. Below a 1/16 setting they just go OFF.

I don't think the XPro trigger is any different, but can program the power in 0.1 stop increments like the rear control (the R2 triggers are 1/3 stop only).

To achieve the range to 1/128 or 1/256 almost certainly requires narrow pulse control of the flash tube, which would require IGBT technology and drive the price point up into the higher range.

I've spent lots of time, $ and energy studying the design and inner workings of many strobes, these included and even disassembled them. The strobes with the IGBT technology that I'm familiar with are the XPLOR 600 and RAPID 600, the Studio 300 use a different means to control the output.

Best,

Mike
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Fri Jan 05, 2018 9:58 am    Post subject: Reply with quote

Ted,

Some Studio 300 Strobe (Godox SK300II) details that may help.

Early last year I selected these as my "go to" studio strobes after looking into many options. I subsequently disassembled, studied and measured the inner working of these strobes (upon which I recommended them), to make sure my selection was the correct one.

First off, I found the design to be very good and built quality and circuit boards to be exceptional for this price range, outstanding value IMO (thus my recommendations).

The maximum available energy for an optical output is stored in capacitors and this strobe uses twelve 330uF 400V rated caps.

Energy = 1/2*(C*V^2), so at rated voltage this equals ~317WS. I measured ~388 volts across the caps at full output setting, thus 298WS. So they are as rated 300WS.

However I did measure at other settings and without an oscilloscope to verify the pulse widths, these can't be taken as absolutely accurate. I did find the voltage at 1/16 setting to be ~143V or ~40WS, not 300/16 or 18.75WS and at 1/4 ~229V or 104WS not 300/4 or 75WS.

Anyway I've characterized the Studio 300 for my use, I suspect other strobes and speedlights follow a similar pattern, but without a scope to verify the actual waveforms I can't assure this.

Best,

Mike
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tevans9129



Joined: 30 Nov 2017
Posts: 99
Location: TN

PostPosted: Fri Jan 05, 2018 10:06 am    Post subject: Reply with quote

mawyatt wrote:
Ted,

I don't think you can get these strobes to go below 1/16 power. I know this for sure with the R2 triggers and from the rear controls on the strobes. Below a 1/16 setting they just go OFF.

I don't think the XPro trigger is any different, but can program the power in 0.1 stop increments like the rear control (the R2 triggers are 1/3 stop only).

To achieve the range to 1/128 or 1/256 almost certainly requires narrow pulse control of the flash tube, which would require IGBT technology and drive the price point up into the higher range.

I've spent lots of time, $ and energy studying the design and inner workings of many strobes, these included and even disassembled them. The strobes with the IGBT technology that I'm familiar with are the XPLOR 600 and RAPID 600, the Studio 300 use a different means to control the output.

Best,

Mike


I just made another test as follows.

1/30, ISO 100, Xpro set to 1/128

1/30, ISO 100, Xpro set to 1/16

RAW format and the RAW looks about the same to my eyes as does the JPEG.




The display on the stobe reads 1/16 for both shots but there sure looks like less exposure at 1/132 than at 1/16, what do you think?
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Fri Jan 05, 2018 10:20 am    Post subject: Reply with quote

tevans9129 wrote:
mawyatt wrote:
Ted,

I don't think you can get these strobes to go below 1/16 power. I know this for sure with the R2 triggers and from the rear controls on the strobes. Below a 1/16 setting they just go OFF.

I don't think the XPro trigger is any different, but can program the power in 0.1 stop increments like the rear control (the R2 triggers are 1/3 stop only).

To achieve the range to 1/128 or 1/256 almost certainly requires narrow pulse control of the flash tube, which would require IGBT technology and drive the price point up into the higher range.

I've spent lots of time, $ and energy studying the design and inner workings of many strobes, these included and even disassembled them. The strobes with the IGBT technology that I'm familiar with are the XPLOR 600 and RAPID 600, the Studio 300 use a different means to control the output.

Best,

Mike


I just made another test as follows.

1/30, ISO 100, Xpro set to 1/128

1/30, ISO 100, Xpro set to 1/16

RAW format and the RAW looks about the same to my eyes as does the JPEG.




The display on the stobe reads 1/16 for both shots but there sure looks like less exposure at 1/132 than at 1/16, what do you think?


Yes it does! However at 1/128 it should be black compared to the 1/16 image!!

Try an exposure with both the strobes OFF and see what you get, then at 1/128, 1/64, 1/32, 1/16, 1/8, and 1/4.
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mawyatt



Joined: 22 Aug 2013
Posts: 1130
Location: Clearwater

PostPosted: Fri Jan 05, 2018 10:46 am    Post subject: Reply with quote

Ted,

I can confirm that my 4 Studio 300 strobes DO NOT change output when using the R2 transmitter and programming anything below 1/16 output, they are the same output as 1/16 power. When the control knob on the strobe rear panel is turned past 1/16, then display goes "--" and the test button does NOT fire the strobe, they won't fire until a reading on the rear panel is 1/16 or higher.

Anyway, this is the way my strobes work with the R2. Since I don't have a XPro I can't say for sure, but seriously doubt that the Xpro can make these Studio 300 strobes actually deliver anything below 1/16 output. The electronics side of this wouldn't make sense if they actually did go below 1/16 with the Xpro.

Let us know what you find?

Best,

Mike
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tevans9129



Joined: 30 Nov 2017
Posts: 99
Location: TN

PostPosted: Fri Jan 05, 2018 10:50 am    Post subject: Reply with quote

mawyatt wrote:


Yes it does! However at 1/128 it should be black compared to the 1/16 image!!

Try an exposure with both the strobes OFF and see what you get, then at 1/128, 1/64, 1/32, 1/16, 1/8, and 1/4.


OK, starting with strobe off and then progressing up from there.










The only change was to reduce the size and convert from RAW to JPEG, what are your thoughts?
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