Am I crazy with this flash idea? D/eGN flash mode?

[photom]

I asked this elsewhere and did not get a response so I thought I would try

again here. Otherwise I will accept it as a crazy idea and go on.

 

Since all the newer lenses for DSLR capture and transmit distance (D) and

aperture information, (and it knows ISO) why can't we have a pure D/eGN flash

mode where we manually plug in various effective GN (eGN) settings in advance

based on tests with other variables such as, diffusers, reflectors, angle,

bounce, etc. Ten or so of these eGNs are stored in the camera memory along

with a short descriptive title sorted by most commonly used. We select one of

the eGN settings already stored and the flash automatically powers down just

the right amount based on the distance, aperture, ISO, and eGn selected.

Perhaps would even have an option to compensate the distance data if the flash

is moved off camera say 3 ft. closer, for example. D> -3.

 

I would love this and obviously this could be done easily. No sensor required,

avoids pre-flash and TTL. Not fooled by dark or light objects (assuming

original test was done correctly on mid-tone target).

[pico]

The answer, Mr. Reynolds, is that there would be a market of one, you, or at least not enough

users to be a compelling feature. How many people really need or care for it? And look at it

this way - you can do the same simple math in your head. It's even HARDER to come to terms

with the in-camera OS to do the same.

 

IMHO, of course.

[richard_cochran]

This is the way the old Nikkor GN 45 f/2.8 lens works, though it was through a mechanical coupling between the focus ring and aperture ring. By focusing on your subject, you automatically set the correct aperture for the GN of your flash. This lens is still available used, and it still works well. It's not fooled by the situations that will fool any reflective flash metering scheme.

<p>

A problem with your enhancement is that the Guide Number equation only holds for direct on-camera flash pointed straight at the subject. The GN equation depends on the fact that the intensity of a point source light falls off with the inverse square of distance, and it relies on the fact that, for direct on-camera flash, the flash to subject distance is equivalent to the lens to subject distance as measured by the lens focusing. If you're bouncing, or if you move the flash off camera, then the light no longer falls off with the inverse square of <em>focused</em> distance, since it's travelling a different path. If you're diffusing very much, the light is no longer close enough to a point source for the inverse square law to accurately apply. In fact, if you move the flash off camera, you most likely have it on a stand somewhere, and in this scenario, as you move the camera around and refocus, the exposure stays constant regardless of the camera to subject focused distance.

<p>

Maybe I'm wrong, but I don't think there's a huge demand for better metering of direct on-camera flash. Today's TTL is usually good enough. The biggest improvement that can be made to most direct on-camera flash photos isn't to improve the metering, but to improve the quality of light by getting the flash off camera, or bouncing/diffusing the light (where the GN equation won't work well).

<p>

Furthermore, with DSLRs, it's usually not <em>that</em> hard to take a test shot, review the histogram, and fine tune the exposure.

<p>

So you're not crazy; your idea would be of some use, but I wouldn't hold my breath waiting for camera manufacturers to re-implement it.

[kin_lau]

I would like something like this for wildlife/bird photography where any flash used is always direct, and where completely white birds or bears or dark coloured fur is often the target.

 

Of course, a EV +/- override would be good to account for a Better-Beamer, fill vs main etc.

[ilkka_nissila]

The distance info is only approximate, not useful for basing precise exposure on. Also, direct flash gives poor quality lighting and shouldn't be used in most cases if you want a good image.