Using electronic flash with LF cameras

[tonyowen]

What would a typical flash to subject distance be? and at what f stop would you shoot please?

The corrected GNs are 7.5 and 11.5 so the distances for the aperture son my lens are between 0.86m and 2.45m - see below
6ISO GN7.5=f4.7@1.60m or GN11.5 = f4.7@2.45m.
6ISO GN7.5=f5.6@1.34m or GN11.5 = f5.6@2.05m.
6ISO GN7.5=f8@1.00m or GN11.5 = f8@1.44m.
6ISO GN7.5=f11@0.68m or GN11.5 = f11@1.05m.

regards
Tony

[tonyowen]

If you don’t make sure if your shutter has an M/X lever it is set at X and try again. If not the you need an X synch shutter or your shutter needs service!

MXV shutter recently serviced 'x' contact is synch'd - Shutter set at 'x' by default.
regards
Tony

[Jac@stafford.net]

In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.

[cowanw]

The corrected GNs are 7.5 and 11.5 so the distances for the aperture son my lens are between 0.86m and 2.45m - see below
6ISO GN7.5=f4.7@1.60m or GN11.5 = f4.7@2.45m.
6ISO GN7.5=f5.6@1.34m or GN11.5 = f5.6@2.05m.
6ISO GN7.5=f8@1.00m or GN11.5 = f8@1.44m.
6ISO GN7.5=f11@0.68m or GN11.5 = f11@1.05m.

regards
Tony

Just the way you said that; that is .86 m to 2.45 m flash to subject, not subject to aperture, right?
Bounce can take up an extra stop depending on the ceiling.

[tonyowen]

Just the way you said that; that is .86 m to 2.45 m flash to subject, not subject to aperture, right?
Bounce can take up an extra stop depending on the ceiling.

Aperture is given in the 'table' from f4.7 to f11. The distance range is from f11 with a [corrected] GN of 7.5 to f4.7 with a [corrected] GN of 11.5
Direct no bounce
regards
Tony

[tonyowen]

In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.

Agreed - my flash guns and LF camera work with film (Fomapan 100) without problem.
Also electronic flash is used by others to 'pre-flash' paper negatives.

This is why I'm trying to determine the factors that [might/are/could] preclude my use of electronic flash with paper negatives

regards
Tony

[Pere Casals]

GN = aperture x (flash to object distance (bounced or direct] + distance from lens front to film plane)????

Tony, here you have conceptual issue.

With flashes and GN, the distance from camera to subject is always irrelevant, what is used in de calculation is the distance from flash to the subject, both in 35mm and in LF. In 35mm flash can be not in the camera...

So to apply GN always use flash to subject distance, adding the bounce in the ceiling if it's the case.

What is different in LF is that you have to use the bellows compensation factor, exactly the same factor has to be applied for flash exposure or for (no flash) outdoor shots, for close subjects.

[Pere Casals]

In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.

Jac perhaps (speculating) there is a reciprocity failure factor. LIRF may be present both for long exposures but also for extremly short exposures, and a flash can be 1/30,000 , for example.

"Reciprocity also breaks down at extremely high levels of illumination with very short exposures" https://en.wikipedia.org/wiki/Recipr...rocity_failure

[tonyowen]

Tony, here you have conceptual issue.

With flashes and GN, the distance from camera to subject is always irrelevant, what is used in de calculation is the distance from flash to the subject, both in 35mm and in LF. In 35mm flash can be not in the camera...

So to apply GN always use flash to subject distance, adding the bounce in the ceiling if it's the case.

What is different in LF is that you have to use the bellows compensation factor, exactly the same factor has to be applied for flash exposure or for (no flash) outdoor shots, for close subjects.

QUOTE=Pere Casals;1483086]Jac perhaps (speculating) there is a reciprocity failure factor. LIRF may be present both for long exposures but also for extremly short exposures, and a flash can be 1/30,000 , for example.

"Reciprocity also breaks down at extremely high levels of illumination with very short exposures" https://en.wikipedia.org/wiki/Recipr...rocity_failure[/QUOTE]

Pere, thanks for comments.
However, though the flash duration is short its intensity is large
Using a 135mm lens at circa 2m [lens/flash to subject] the bellows extension is well below 1.5x focal length
So, I should be able to get some 'exposure' on the paper negative BUT I'm getting absolutely nothing.
Hence my posting and persistent questioning.
regards
Tony

[cowanw]

Can you be putting the paper in the dark slide backwards?