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04-10-2019, 04:28 PM   #16
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QuoteOriginally posted by BruceBanner Quote
That helps heaps. I must have fluked things enough with the blending in pp between the two exposures. I went 1/8 to 1/32 and chimped the shots and they looked about the same in brightness so thought I got that right, but then the velvet glow at f2 does make things hard to judge, not just sharpness but brightness/exposure as well perhaps :S

I'll retest today. I love the '3 clicks per stop' and I can run with that.

What about the EV difference flash calculator stuff, I might not always have charts with me for reference etc. Is there any simple maths I can do in my head to find the EV difference? Like.. I know it would get complicated to add in a 2nd and 3rd variable (shutter speed variance and ISO change) but let's for arguments sake pretend that I will only be shifting aperture in this regard, how can I easily figure out of f5.6 >f2.8 is xEV difference, f8>f2.8 etc etc?
You need to memorize the full aperture f stop sequence. It's not hard == 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Each of these values is one stop difference. If your camera is set to 1/3 stop increments, you can simply set one f stop there and then count the clicks until you reach the one you want.

04-11-2019, 03:05 PM   #17
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QuoteOriginally posted by West Penn Quote
You need to memorize the full aperture f stop sequence. It's not hard == 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Each of these values is one stop difference. If your camera is set to 1/3 stop increments, you can simply set one f stop there and then count the clicks until you reach the one you want.
And so with a lens like the lensbaby where it doesn't do f1.4 but f1.6 I should just pretty much round it to the nearest and treat it like f1.4? It would be such a small difference in exposure anyway right?
04-11-2019, 04:50 PM   #18
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QuoteOriginally posted by BruceBanner Quote
That helps heaps. I must have fluked things enough with the blending in pp between the two exposures. I went 1/8 to 1/32 and chimped the shots and they looked about the same in brightness so thought I got that right, but then the velvet glow at f2 does make things hard to judge, not just sharpness but brightness/exposure as well perhaps :S

I'll retest today. I love the '3 clicks per stop' and I can run with that.

What about the EV difference flash calculator stuff, I might not always have charts with me for reference etc. Is there any simple maths I can do in my head to find the EV difference? Like.. I know it would get complicated to add in a 2nd and 3rd variable (shutter speed variance and ISO change) but let's for arguments sake pretend that I will only be shifting aperture in this regard, how can I easily figure out of f5.6 >f2.8 is xEV difference, f8>f2.8 etc etc?
You want the base-2 logarithm of the square of the ratio of the f-stops. Easy, peasy!

The square of the ratio of two f-stops gives the ratio of the light levels:

((F-Stop1)/(F-Stop2))^2

For f8>f2.8, thats (8/2.8)^2 = 8.2.

The change in EV is the base-2 logarithm of that ratio

log2(8.2) = 3 EV

Or you could just count clicks of the e-dial.
04-12-2019, 12:20 AM   #19
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QuoteOriginally posted by photoptimist Quote
You want the base-2 logarithm of the square of the ratio of the f-stops. Easy, peasy!

The square of the ratio of two f-stops gives the ratio of the light levels:

((F-Stop1)/(F-Stop2))^2

For f8>f2.8, thats (8/2.8)^2 = 8.2.

The change in EV is the base-2 logarithm of that ratio

log2(8.2) = 3 EV

Or you could just count clicks of the e-dial.
What part of 'I failed school miserably' did you not follow

I don't even know how to do the ^2 part of the sum on a calculator... there's no hope for me...

04-12-2019, 05:33 AM   #20
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QuoteOriginally posted by BruceBanner Quote
And so with a lens like the lensbaby where it doesn't do f1.4 but f1.6 I should just pretty much round it to the nearest and treat it like f1.4? It would be such a small difference in exposure anyway right?
F/1.6 is 1/3 of a stop smaller than f/1.4, so you're right, you probable wouldn't notice the difference. Or, give it one less click or one more click on the speedlight dial depending on whether you're closing or opening the aperture.
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