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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 23 Oct 2013 (Wednesday) 14:12
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Can someone explain this phenomenon?

 
dbeugel
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Oct 23, 2013 14:12 |  #1

I was lighting white seamless last night with two 400W strobes and wide angle reflectors. Just for fun I turned on highlight alert to see where it was blown out and where it wasn't. However, there was one section on the right hand side of the seamless that always seemed to prevent the blinkies. I even turned up the strobes and still it remained, and you could see the fall off gradient. So I'm not sure why but I switched to landscape orientation and boom the entire top half of the seamless registered black to indicate it was over exposed. Again went back to portrait and yup the right side feathered off again. Here is a rough example below, the black section being the highlight alert. If anyone can explain why I will be hugely grateful! Camera is 5D MkII with Sigma 35mm 1.4 shooting at f/11.

IMAGE: http://images.eu.viewbook.com/3d45aafc1c29a053c8a86232db762fa7_large.jpg

I own a DSLR, some lenses and some lights.

  
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BTNorris
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Oct 23, 2013 14:17 |  #2

I'm guessing this is a "blinkie algorythm" thing and if you opened the images in Photoshop you'd see similar RGB values. I'd start there first with the actual images.


7D, 17-55, 50 1.4, 70-200, 10-22, Kenko Tubes, OPTIX xr, Einstein

  
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gonzogolf
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Oct 23, 2013 14:18 |  #3

What was your sync speed? If you have some trigger delay it would show up as a darkened line on the side in portrait alignment.




  
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dbeugel
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Oct 23, 2013 14:35 |  #4

Hey guys, I was shooting at 1/200 using skyport speed RX! And that's it! I just realised the RX model lights have two modes r.1 1/160 and r.2 1/200 !! And funnily enough when googling the modes a POTN thread came up with this...........

https://photography-on-the.net/forum/showthre​ad.php?t=879322 !!

He was worried about his shutter line being angled but funnily enough mine is too! But when using my pocket wizards with speedlites the black bar is perfectly straight!!

Thank You!


I own a DSLR, some lenses and some lights.

  
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abbadon31
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Oct 23, 2013 14:44 |  #5

your catching the tail of the flash and your sync
5dmkIII I have to shoot at 1/125 and the 7d i can use 1/250 using the skyport speed


I AM SHOM

  
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dbeugel
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Oct 23, 2013 14:45 |  #6

abbadon31 wrote in post #16393450 (external link)
your catching the tail of the flash and your sync
5dmkIII I have to shoot at 1/125 and the 7d i can use 1/250 using the skyport speed

Wow?! 5D MkIII is 1/125 with the skyport speed?!


I own a DSLR, some lenses and some lights.

  
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gonzogolf
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Oct 23, 2013 14:49 |  #7

dbeugel wrote in post #16393456 (external link)
Wow?! 5D MkIII is 1/125 with the skyport speed?!

Just so you understand that there would be no discernible difference in a studio image at 1/200 and 1/60 unless you have some serious ambient contribution. So dont get caught up in studio sync speed.




  
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dbeugel
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Oct 23, 2013 14:53 |  #8

gonzogolf wrote in post #16393466 (external link)
Just so you understand that there would be no discernible difference in a studio image at 1/200 and 1/60 unless you have some serious ambient contribution. So dont get caught up in studio sync speed.

Thanks Gonzo yeah I realised I could get away with lower but thought without shooting for a black frame I shall just whack it on 1/200 ! I've been so used to the pocket wizards being perfect at 1/200 I completely forgot I had to set my strobes to 'speed' mode!

So If I understand it right, the dark line is the shutter but it's angled because it's the tail end of the flash right?!


I own a DSLR, some lenses and some lights.

  
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abbadon31
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Oct 23, 2013 15:00 |  #9

The gradient is from tail
if your shooting white background point your light inwards. I aim mine corner to corner cross the middle


I AM SHOM

  
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dbeugel
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Oct 23, 2013 15:08 |  #10

abbadon31 wrote in post #16393499 (external link)
The gradient is from tail
if your shooting white background point your light inwards. I aim mine corner to corner cross the middle

Cheers Scott, I struggle a bit with lighting the background, I have very limited space and tend to get quite rapid fall off making it a total PITA!!! I can see why the Lastolite HiLites sell do damn well!


I own a DSLR, some lenses and some lights.

  
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Curtis ­ N
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Oct 23, 2013 16:46 |  #11

dbeugel wrote in post #16393456 (external link)
Wow?! 5D MkIII is 1/125 with the skyport speed?!

The Skyports have more lag time than some of the other popular radio triggers. The way to prove or disprove this is to try the same shots with a PC cord instead.


"If you're not having fun, your pictures will reflect that." - Joe McNally
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dmward
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Oct 23, 2013 21:41 |  #12

abbadon31 wrote in post #16393499 (external link)
The gradient is from tail
if your shooting white background point your light inwards. I aim mine corner to corner cross the middle

This is important to remember. Light falls off from the center to edges of cone for all reflectors. Scott's suggestion is using the edge of each light combined to light the middle and the middle of each light to illuminate the opposite side. Its the best way to get a smooth light spread across a background.

I found the easiest way to aim the lights it point the center of the light about half way or a little past the 1/3 point past the center.


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abbadon31
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Oct 24, 2013 14:10 |  #13

Cross keeps keeps from having a hot spot. Once you start adding more lights into the mix you increase the exposure. If I pointed the back light at center and then add the main, fill, and hair light I would have increase the background reading unless I flag off all the lights from hitting the background.


I AM SHOM

  
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dbeugel
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Oct 24, 2013 15:10 |  #14

What about having the 'perfect blown white' around the subject and placing the fall off areas somewhere easy to fix in post. In many white seamless pics I can ALWAYS pick out the outline where they've brushed around the model without going in close


I own a DSLR, some lenses and some lights.

  
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gonzogolf
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Oct 24, 2013 15:32 |  #15

dbeugel wrote in post #16396168 (external link)
What about having the 'perfect blown white' around the subject and placing the fall off areas somewhere easy to fix in post. In many white seamless pics I can ALWAYS pick out the outline where they've brushed around the model without going in close

In many you can always... Something doesnt add up here. Perhaps you can often find the outline?




  
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Can someone explain this phenomenon?
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