Exposing for Off Camera flash ??

[bigdazzler]

ok so i got all my bits finally (see here) and the triggers are working. They seem to be firing the off camera flash pretty consistently with both the test button and the shutter. So no problems with the mechanics. Problem is exposure.

Ive now noticed with just a few play shots that the exposure is very very blown out. Im pretty new to exposing with flash so any tips or advice appreciated are much appreciated

In the semi manual modes (A and S priority) my cameras flash menu consists of

1. Fill
2.Slow Sync
3. Rear Sync
4. Wireless

Same options in full manual.

I also have the option of Pre-TTL flash and ADI.

When I use the onboard flash to trigger the off camera flashgun, I have the camera and flash set to optical wireless mode which relies on infrared to send and recieve the trigger signal, and the exposures seem spot on for the most part.

Now when using the new triggers, im not sure how to set it all up and get correct exposure , all the test shots ive taken are WAY blown ??? Can anyone steer me in the right direction oh and my flash is fully automatic, no manual power settings ..

[TEITZY]

I assume with the triggers it will be all manual settings (no TTL) if they are connected via a PC cord? If this is the case you need to set the flash power or aperture manually on each flash.

Cheers
Leigh

[bigdazzler]

mmm yea Leigh thats what i figured ..

so when using triggers youve got no TTL at all right ?? my flash is connected to the receiver with a sync cord , transmitter is on the camera hotshoe ..

if theres no TTL metering, how do you measure your exposure ?? Do I need a handheld flash/light meter ?? If so, i think im screwed here anyway, as this particular flash has no incremental power settings, its all auto ..

[TEITZY]

Darren I think the new radio poppers or PW's do have a TTL option but not these guys. Funny that your flash doesn't have any manual power or aperture settings - that could be a problem (if power is always the same, you will need a light modifier to match your camera settings).

You will need a light meter or trial and error to work out the right settings. With the SB800 I can adjust aperture and ISO to correspond with my camera settings to get the right exposure (close to anyway).

Cheers
Leigh

[bigdazzler]

mmm .. nah no such luck here, the Sony 36AM is their base flash, no manual at all

[TEITZY]

So I assume the flash is just firing at full power and hence the blown exposure. In a studio set-up where you are shooting pretty constant aperture and ISO, the appropriate diffusion on each flash is workable, though you will be possibly using more power than you need (particularly on the fill or kicker light). However things become a bit more tedious if you want to mix things up a bit in the studio or use this setup elsewhere.

Cheers
Leigh

[bigdazzler]

yep seems im gonna have to find a suitable light modifier or upgrade my flash to get out of this pickle ..

When i use the flash off camera with the onboard as a trigger, exposure is great .. but im assuming thats because im benefiting from TTL metering ..

I have a shoot through brolly ill have a play with and see if i can diffuse it enough that way to get some kinda result .. im not confident though as these shots are WAY blown .. like WAAAAAY blown beyond recognition , maybe a small DIY soft box ??

[TOM]

Hi Darren
Firstly, you need a flash/light meter. You can get away without using way just by chimping, but this is not as accurate and less efficient. In manual mode for your flashes, you want to have your camera in manual mode. With flash photography, the shutter speed has no effect on the exposure of your subject. That is biggest thing to get your head around when learning flash. It is a different way of thinking compared with natural light photography. The shutter speed will only control the background exposure. This is great because it allows you to get really creative. I prefer to underxpose the background by about one to two stops but that is only my preference and certainly not a hard and fast rule. Digital photography may not be as good as film photography, but experimenting with flash is one area where it is a real advantage.

So eventually you will instinctively know what power to set your flash at for a given distance/aperture (give or take), and the flash/light meter will be for fine tuning. Another reason to get a flash meter is for working out lighting ratio's, particularly when the strobes are not equal distances from the subject. The closer you have your flash unit, the more wrap around light you will get. You will need to shoot through an umbrella or soft box to get close to pro lights, which can be acheived to good effect. Remember however that your camera speedlight has around 30w/s and a good studio strobe has upward of 500w/s. You do need to turn the power of you flash down, or move it away from the subject.

BTW, pocket wizards do not do TTL except for the very latest ones that haven't been released yet, or have just been released.

[bigdazzler]

Thanks Tom, some good info there .. particularly the thing on shutter speed.
So given I dont have a flash meter, and I cant adjust my flash manually .. pretty important things to be lacking i realise .. hahah

Is there a way i can play around with my triggers and brolly and get any kind decent result. I would like to shoot some off camera portraits with like a standard camera>flash(45degrees)>model kinda setup ..

Would I benefit from placing the brolly and flash further away from the model given the full power only output ??

im just trying to spitball here to be able to use what I have at my disposal for now ..

[TOM]

Darren, I didn't pick up on that in the above threads. Are you saying that your flash can only output at full power? That would be most strange. What is the brand and model?

[bigdazzler]

yea i just have the Sony36AM mate .. its Sonys entry level base flash .. no manual power increments/decrements , only full power .. unless im totally missing something

[arthurking83]

Hi Darren
Firstly, you need a flash/light meter. You can get away without using way just by chimping, but this is not as accurate and less efficient. In manual mode for your flashes, you want to have your camera in manual mode. With flash photography, the shutter speed has no effect on the exposure of your subject. That is biggest thing to get your head around when learning flash. It is a different way of thinking compared with natural light photography. The shutter speed will only control the background exposure. ...

Errr..

you sure about that TOM?

I was just playing with my flash, and shutter speed was everything!
Foreground, subject, and background were all affected by differing shutter speeds, and in full power manual mode, I had to shoot at speeds of 1/4000, to get subject not wildly blown out(at 2meters mind you).. but that's a common distance for portraits.

I'm the first to admit that I'm a complete noob when it comes to flash photography and I spent all day yesterday intimately acquainting myself with it all.. and coming to the realisation that not only can it be important(in some instances), but that I now have an urgent need for a SB-900(of course two would be better) in addition to my current SB-800(I was thinking of selling it to fund the urgency of a SB-900.(why is it that photo gear always seems to find it's way to the top of the 'to do' list )

Anyhow.. in manual mode for the SB800(wireless mode), and set to full power, anything less than 1/2000s and f/8 at 2meters is going to be blown out(there's a lot of white on my test subject... a door!)

Of course in TTL mode of any kind whether it's balanced fill or spot metered, the camera/flash automatically adjust themselves appropriately to achieve the desired exposure. And funnily enough whilst in manual mode and shooting @ 1/8000s .. I never saw any shutter curtain issues? First time I'm shooting past FP sync speeds(I have the D300 set to 1/320s and have never needed more) and I doubt that the flash is somehow compensating.. I was kind of disappointed not to see some shutter curtain

Sorry Darren, but I'm your last best hope for any answers.
Does your Sony allow you to shoot at faster shutter speeds than FP sync speeds in manual mode(with flash that is).

So try full manual mode for the camera, and we'll assume that the flash is just going to provide full power(just as I set my remote flash).. keep increasing shutter speeds and or aperture and lets see what happens?

Note: hopefully the Sony will allow you to shoot past 1/160s sync speed, otherwise you need to spend more $$$$$$$ on a better flash.

I couldn't get my head around it all yesterday trying to do real estate interior shots for my sis!
Damned missed out on catching up with BigBikes!

[TOM]

yes the flash fires at such a fast rate that the shutter speed has no affect on the subject. the flash fires at around 1/10000s and that is what exposes the subject. then if you drag the shutter, then that will affect the background (or foreground in certain instances). what is the key to adjusting the look with flash is the flash power, the distance, and the aperture. you can make an image shot in the afternoon look like it was shot at night by setting the shutter to a much faster speed than you would for a natural light shot. so fast that it would be virtually all black due to underexposure. then add just enough flash to illuminate your subject and you will have a night time shot taken in the middle of the day. this may help you get your head around flash.

Darren, try decreasing the aperture and see how that affects your image. take a shot at the at f4 and then at f16 at the same distances/power. this will make a dramatic difference. make sure you shoot at or under your sync speed.

[bigdazzler]

ok i just switched on the camera , set it to manual , SS 160th (max sync speed) ,and then took three shots at 5.6 , 8 , 11 ... The exposures are much better than my earlier playing around.
The histogram says the shot at 5.6 is much more evenly exposed and the other two, are as expected, slightly underexposed.

Just going right back to basics for a sec .. i should totally disregard the meter indicator on the LCD right ?? cause its not doing anything , ie no TTL ??

I just wanna make certain that in real terms, when using the triggers, my cameras meter is doing nothing right ??

[TOM]

darren that is correct. you can use your camera meter to give you an idea of the ambient light and set accordingly, but take the meter reading at the aperture that you intend to shoot the image with. again, this will have no affect on your subject, only the background light. with a meter, what you would do is fire the flash at the given power ie. full power, 1/2 or 1/32 etc, whilst holding the meter on the subject. it will then tell you the correct aperture to get the right exposure for your given power setting and flash to subject distance.

if you were taking a shot with a white background and you wanted that certain look, you choose a long shutter speed to overexpose the background, blowing it out to give that high fashion look. the possibilities are endless.

[CAP]

I have a Minolta 3600HS-D flash which is basically the same as The Sony 36AM.
Just checked and double checked, what Darren says is correct, there is no way to manually adjust the output of the flash.

Side story.
I also have a 5400HS flash from the 800-si film camera.
In it's day the 5400HS was Minolta's premium flash unit, with zoom, tilt, swivel, high speed sync, variable output, modelling modes etc.
Was shattered when I found out it was incompatible with the Minolta-7D and not surprised to find it's functions are not supported by the A-700 either.
This unit will sit around until I venture in to off camera flash, gonna make for a hell expensive slave flash but.

[bigdazzler]

you got me thinking about how shutter speed doesnt effect the exposure of the subject so i tried a little experiment ..

set my camera to M, ISO100, f11 and took five shots. I see a difference in the overall exposure between 1/160th and 1/80th. However, 1/80th , 1/40th, 1/20th, 1/10th exposure and histograms look identical ..

1/160th

1/80th

1/40th

1/20th

1/10th

[TOM]

CAP, that's a shame. Darren, for off camera manual flash, you don't need anything fancy. Go and buy a used Nikon SB-26 or even a new Nissen or cheap flash. It is going to do roughly the same job as a huge Metz flash for a fraction of the price. You won't be paying for wireless CLS, TTL et al. All you need is a flash that can do manual control.

[TOM]

Darren, in your shots, the background is affected by the flash because it is so close to the subject. This shot was mostly fill, but it is darker that you think. The flash could have no affect on the background here, unlike your shot where the flash will illuminate everything.

[bigdazzler]

ok now further to my experiment above with shutter speed .. ive just done the same thing with adjusting the aperture by one stop each shot ..

manual , ISO100, 1/160th, f5.6 ... then 4 more shots stopping down one full stop each time .. Whereas shutter speed had no effect on overall exposure of subject, adjusting the aperture seemed to have a BIG effect ..

f5.6

f8

f11

f16

f22


what I think ive determined is that the shutter speed has much less of an effect, if any, on the exposure of the subject .. and the aperture has a great effect .. trying to get my head around this ... mmm