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11

Flash duration is typically much shorter than most cameras' flash sync speed. If the flash only has a duration of, say, 1/1000 second (or 1 millisecond), it matters not if the shutter is open 1/250 second (4 milliseconds) or 1/25 second (40 milliseconds), the energy from the flash that is captured by the photo will be the same in either case. What shutter ...


5

The simple equation assumes that the flash is effectively the only source of light in your image. This is a reasonable assumption in many cases, because since exposure works on an exponential scale, the amount of light from typical indoor room lighting is a drop in a bucket compared to that provided by the flash. See Do flash guide numbers assume some ...


4

It sounds like the scene your were framing was outside the operating range of your 80D's meter. It's rated for EV 1-20. At ISO 100, EV 1 is equal to f/1 for 1/2 second.¹ The maximum ISO for the 80D is 25,600. That's 8 stops higher than ISO 100. f/8 is six stops darker than f/1. You report that 30 seconds was a good exposure time for ISO 25,600 and f/8....


4

This material has super low sensitivity to light. Additionally, it has no sensitivity to red so you can use a safelight. Assume an ISO of 2. The sunny 16 rule of thumb is workable. This will be: Shutter speed is 1 over ISO – this shutter speed is ½ second at f/16 in bright sun. Applying the reciprocity law – your trial exposures can be any of the ...


2

If you use a directional light, and we make some assumptions, we can roughly calculate the shutter speed for the ISO and f stop in your comment. As a sanity check, here is the calculation for my test setup. It is a stop off, so some of the assumptions aren't correct. This is only a ballpark calculation anyway. More comments on my test setup. A typical ...


1

Sunlight is exposure value = 15. It's about 100 000 lux. So, with e.g. about 100 lux you get exposure value = 5, because every doubling of brightness increases exposure value by 1 and every halving of brightness reduces it by 1. 1000 is approximately 10 doublings (well, ok, to be exact, 10 doublings is 1024). However, LED lights have their output specified ...


1

We use the Guide Number as an aid to gauge the f-number setting. Accept, as an example, your ISO setting is 200. You consult a table of guide numbers and discover it’s 180. Your principal subject is 10 feet downstream of the flash. What would be the appropriate f-number setting? To compute, we divide guide number by distance -- thus 150 ÷ 10 = 15.5. Now ...


1

Both of the other answers are correct, but I think there might be an easier way to understand it: Consider being in a completely black room with no light... the shutter can be open indefinitely because there is no light available. The only thing that matters is that the shutter is fully open when the flash fires so that all of the sensor can see it. The ...


1

Two important points you have to keep in mind: The dynamic range (DR) of PO film is incredibly narrow. It is even more limited than slide film The OneStep 2 allows for barely any precise exposure compensation, unless when shooting in manual mode. The first point is likely the reason your photos are oftentimes partially under- or overexposed. In case you ...


1

I would add that it could be a sticky aperture problem. Whilst in DOF mode the aperture blades did close, during the fast shutter moment, it may not have enough time to react. I had a similar problem with one of my yongnuo lenses. I could temporarily remedy the problem by repeatedly doing a DOF preview until the aperture blades had loosened. When I took ...


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