alistair_kerr2

I'm taking photographs of a domestic room interior, which I'm trying to light

at a 1:4 ratio using an Elinchrom 500 monolight with the ambient source being

daylight. I'm using a Sekonic L508 meter. A typical ambient reading (for the

part of the room which needs the fill light) is around 8 sec's at f11 at ISO 100

(Nikon D200 DSLR with 12-24 at 12mm). The brighter part of the room, near the

window, is around 1 sec at f11.

With the meter set to corded flash mode, firing the strobe at full power gives

readings of around f11.

The Sekonic instruction manual states that the value displayed by the meter "is

the sum of the flash portion and the ambient light portion".

My question is, How can I be confident that the ratio of fill flash:ambient

light is 1:4 if there is an unknown component of ambient light in the flash

reading? If the strobes were the main light source, eg in a blacked out room,

shutter speed would obviously not come into the equation - so I am unclear at

what point, and to what extent, the ambient light starts to affect the

flashmeter reading. Clearly only a very small proportion of the relatively

dull ambient light will make a contribution to the reading during the 1/2000

(or whatever) strobe burst, but does it need to be taken into account? When I

change the shutter speed on the meter from 1/250 (sync speed) to slower speeds

such as 1 sec, there is a difference of anything up to 1/2 stop. Presumably if

I was able to set the meter's shutter speed to a longer speed such as 10 secs

or more there would be even more of a difference - on the L508 it is not

possible to set the shutter speed for anything longer than 1 sec so I can't

assess this.

Sorry for the long post but any clarification would be appreciated - thanks.

"Why not just use the window light, which should produce a realistic effect, and give a burst of flash on to the darker area of the room? Obviously not at full power, othewise the lighting will be too flat".

Garry, thanks for your reply - maybe I'm not explaining myself clearly, but as I understand it, what you're suggesting is exactly what I'm proposing to do, with the flash at 1/4 the level of the ambient to retain details in the shadow areas etc? The difficulty is in establishing what the actual flash reading is so that I can compare it to the ambient.

I'm hoping to get some work doing interiors for upmarket estate agents sales

brochures and am looking at purchasing some flash units. I can't spend a

fortune on these but I am prepared to spend a sensible amount to future-proof

the investment rather than being short-sighted about it.

I'd appreciate some help on selecting the type of equipment as I've had

conflicting advice from different sources: my first query is, monolights or

packs? The second is, numbers of heads and required power for these? A few

points to throw in to help direct responses...

- I don't live near a rental centre so need to purchase, ie I need to get it

right first time! (UK based);

- lights also need to be suitable for portraiture and studio work;

- I work with 35mm and MF equipment at present but realise that large format

is probably going to be essential in this area, so lights need to be powerful

enough to cope;

- I may also do work for local architects (of which I am one myself) - these

may include progress shots on construction sites where there will be 110v

available so I presumably need bi-voltage units for this reason alone though

not necessarily for trips abroad!!

- I had previously understood that I'd be fine with a couple of heads of

around 600 - 750w/s each. However looking at some other threads it looks like

this is really under-estimating the required power and numbers (I don't really

want to be having to use multiple pops of flash all the time to get the

required levels);

- I'd appreciate a good range of adjustment eg 6-stops so that I can modify

the output without too much messing around with fittings;

- I had thought that monolights would be fine as I'll have access to power in

most locations but some other threads seem to refer to use of packs quite a

bit;

- I'm really looking for general recommendations rather than manufacturer-

specific recommendations (although I have a slight bias towards Elinchrom

units based on their reputation).

Many thanks for your help!