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Need help with strobes.
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19090
Location: Richland, Washington State, USA

PostPosted: Fri Jan 12, 2018 3:52 pm    Post subject: Reply with quote

tevans9129 wrote:
T------F----ISO
4-----25---1000
.3s---25---800
.4s---25---640
.5s---25---500
.6s---25---400
.8s---25---320
1s----25---250

Interpreting that initial "4" as 1/4 second = 0.25, then these numbers are exactly the sort of thing that I would anticipate for metering continuous illumination. At a fixed f-number of f/25, 1 second at ISO 250 is equivalent to 0.5 seconds at ISO 500, and so on for all the other numbers.

None of this seems relevant to flash. To be honest, I'm wondering if the meter was even set to measure flash, when you reported that "Just checked with a 478DR-U and the readings are 1.3s0 at 1/16 and 1.6s3 at 1/128. So there is a difference in time."

Quote:
...decided to go back to the setup that I was using when I first noticed a difference from 1/128 to 1/16, which was….

D800e, Vivitar 2x TC, PB6 at full extension and Amscope 4x.

There was no discernable difference with the NEF files but there was in the JPEG files, not a full stop but definitely a difference in exposure. It seemed to be more pronounced when underexposed for some reason.

I'm not sure that I'm reading this properly. Does this mean that you were able to reproduce this difference, even when capturing NEF and JPEG at the same time? If so, then I would still be interested to get access to those files, say via Dropbox or wesendit.com to support@zerenesystems.com .

--Rik
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mawyatt



Joined: 22 Aug 2013
Posts: 1510
Location: Clearwater

PostPosted: Fri Jan 12, 2018 4:09 pm    Post subject: Reply with quote

tevans9129 wrote:
mawyatt wrote:


Ted,

Great game, kinda felt bad for the Dawgs since they haven't won a Football National Championship in some time, and now Bama has 6 of the last 10 I think. Agree about the call, and the young man made Saban look like genius Rolling Eyes Wish the Gators would wake up Sad

No need for an apology, electronics is something I know quite well. When in elementary school at 9 I had my parents take me to the library to get every book on electricity I could find, by 12 my room looked like something from Back to Future and had my ham rig, by 13 had a oscilloscope and fooling around with transistors, so on (wait I don't even have a scope now Crying or Very sad

I've been teaching (hiring my best students!!) and mentioning for a long time.

Anyway, glad you've got this all sorted out and getting some great images with your WeMacro setup, AmScope 4X and SK300II's!!

Best,

Mike


Thanks Mike, your interest in electronics is 180 degrees out of phase with mine. I have always been handy with my hands but never had an interest in electronics beyond turn the switch on and something happens...hopefully good. So what did I do as a career....30 plus years in information technology. I had a fellow tech that was very skilled with electronic equipment that I played guitar with so naturally asked him to look at my amp that stopped working. He called me up laughing about my profound problem....a blown fuse.

Who was that writer that claimed the SEC was overblown and the Big 10 was thumping everyone...I wonder how he liked the championship game.


Ted,

I repaired and modified Guitar amps, actually all sorts of music equipment to work my way thru college (put the first Cry Baby Wahwah on a Hammond B3 back in ~1968, wow did that sound cool). Still have an old Les Paul (actually a natural walnut version called The Paul I think). Don't play anymore though.

Best,

Mike
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tevans9129



Joined: 30 Nov 2017
Posts: 129
Location: TN

PostPosted: Fri Jan 12, 2018 4:50 pm    Post subject: Reply with quote

rjlittlefield wrote:


None of this seems relevant to flash. To be honest, I'm wondering if the meter was even set to measure flash, when you reported that "Just checked with a 478DR-U and the readings are 1.3s0 at 1/16 and 1.6s3 at 1/128. So there is a difference in time."


Well, I think it was, when the flash was triggered, the screen lights up with the readings for a few seconds and then goes dim until the next flash is triggered and the new readings appear so I assume that it was reading flash.

Quote:
...decided to go back to the setup that I was using when I first noticed a difference from 1/128 to 1/16, which was….

D800e, Vivitar 2x TC, PB6 at full extension and Amscope 4x.

There was no discernable difference with the NEF files but there was in the JPEG files, not a full stop but definitely a difference in exposure. It seemed to be more pronounced when underexposed for some reason.


rjlittlefield wrote:
I'm not sure that I'm reading this properly. Does this mean that you were able to reproduce this difference, even when capturing NEF and JPEG at the same time? If so, then I would still be interested to get access to those files, say via Dropbox or wesendit.com to support@zerenesystems.com .


Sorry I was not clear, using D800e, Vivitar 2x TC, PB6 at full extension and Amscope 4x and shooting in NEF there was no discernable difference in 1/128 to 1/16 on the Xpro but there was a discernable difference when shooting in JPEG and setting 1/128, 1/64, 1/32 and 1/16 on the Xpro.. As I said, the difference seemed to be more profound in JPEG when under exposed somewhat.

Is this any clearer?
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Fri Jan 12, 2018 4:53 pm    Post subject: Reply with quote

Clear enough, thanks.

--Rik
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tevans9129



Joined: 30 Nov 2017
Posts: 129
Location: TN

PostPosted: Fri Jan 12, 2018 4:58 pm    Post subject: Reply with quote

mawyatt wrote:


Ted,

I repaired and modified Guitar amps, actually all sorts of music equipment to work my way thru college (put the first Cry Baby Wahwah on a Hammond B3 back in ~1968, wow did that sound cool). Still have an old Les Paul (actually a natural walnut version called The Paul I think). Don't play anymore though.

Best,

Mike


Well, I did a very complex modification one time, I installed a bridge pickup in a Martin D76. Very Happy

I sold my last two guitars, the D76 and a 1976 Gibson L5 custom a year or so ago to buy camera equipment as I could not play them worth a hoot anyway. Crying or Very sad
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mjkzz



Joined: 01 Jul 2015
Posts: 838
Location: California/Shenzhen

PostPosted: Sun Jan 14, 2018 5:42 am    Post subject: Reply with quote

I have seen so many discussions on flash, flash duration, HSS, etc. From my past experience, you can build a "light meter" using simple components and use sound card to plot the graph of it.

Schematic is Here

Sample graph is HERE Thouhg I think I lost the code for the graph plotting application, you can use the free software Audacity to plot it and recombine them.

I think this will provide some sort of quantitative (relative) measure (might not be absolute, ie absolute EV reading).
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