Exposing for Off Camera flash ?? [Archive] - AusPhotography:: Australia's Premier Photography Forum::

bigdazzler

10-03-2009, 2:08pm

ok so i got all my bits finally (see here (http://www.ausphotography.net.au/forum/showthread.php?t=26087)) 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 :confused013 oh and my flash is fully automatic, no manual power settings ..

TEITZY

10-03-2009, 2:25pm

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

10-03-2009, 2:32pm

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

10-03-2009, 2:45pm

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

10-03-2009, 2:55pm

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

TEITZY

10-03-2009, 4:45pm

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

10-03-2009, 6:31pm

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

10-03-2009, 7:05pm

bigdazzler

10-03-2009, 7:42pm

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 :o

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

10-03-2009, 7:52pm

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

10-03-2009, 8:05pm

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

10-03-2009, 8:16pm

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.. :confused:

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 :D)

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

10-03-2009, 8:31pm

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

10-03-2009, 9:33pm

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

10-03-2009, 9:44pm

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

10-03-2009, 10:27pm

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

10-03-2009, 10:31pm

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
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09138.jpg
1/80th
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09139.jpg
1/40th
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09140.jpg
1/20th
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09141.jpg
1/10th
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09142.jpg

TOM

10-03-2009, 10:32pm

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

10-03-2009, 10:41pm

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

10-03-2009, 10:54pm

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
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09149.jpg
f8
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09150.jpg
f11
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09151.jpg
f16
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09152.jpg
f22
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/DSC09153.jpg

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

bigdazzler

10-03-2009, 11:01pm

Darren, in your shots, the background is affected by the flash because it is so close to the subject..

yep ok Tom , i totally get that bit .. obviously the flash has a certain guide number distance and will only light so far into the frame front to back at any given power output/setting ..

what im trying to get (as in the two sets above) is why the shutter speed has no effect on the subject but the adjusted aperture has a great effect ??

the two sets of images above clearly support what you were saying earlier on about shutter speed and subject ..

TOM

10-03-2009, 11:01pm

precisely, because the flash is, in effect, your shutter and ambient light all rolled up into one little pop that happens at around 1/10000s. Now you shutterspeed is irrelevant and the aperture and distance are the only things that are controlling how much light gets to the film err.....sensor. the shutter speed will have a very minute affect on the exposure but only when we take two images at extreme shutter speeds will we notice this. it is best to work on the basis that shutter is irrelevant.

try a shot of a close object with the background far away. looking forward to some examples. determine the aperture, take one at max sync, then take one dragging the shutter, say four stops under ambient.

bigdazzler

10-03-2009, 11:08pm

ahhhhh ok .. i think im understanding ... so even at 1/10th, the slowest of the shots above, becasue the flash is still firing so quickly, at approx 1/10000th, the ambient light is never going to effect the exposure in the foreground within the flash guide distance .. ?? The burst of flash is simply too bright to be effected by any ambient light in the foreground/subject of the scene ??

am i getting this.. ??

TEITZY

10-03-2009, 11:34pm

Yes the flash will overpower the ambient light in the foreground, however @ 1/10 you should have a brighter background or less light fall off than you would at say 1/100 (that's assuming you are not in a completely dark room). Using low shutter speeds with flash is often referred to as 'dragging the shutter' and it provides a more natural looking shot (with some background detail) while the flash effectively freezes the subject in the foreground. You can also do this by bumping up the ISO as this has basically the same effect as dragging the shutter. So if you have a play with your flash just set the aperture and shutter in manual and change the ISO and see the difference it makes to the exposure.

Cheers
Leigh

bigdazzler

10-03-2009, 11:47pm

ok im getting the idea that the flash will expose the subject and the aperture and distance will determine the ambient light of your background ... handy to know next time I wanna shoot manual fill flash outdoors and want to maintain some background detail.

What about if i want to shoot portraits at say 2 metres with a black backdrop ?? From what i think ive just learnt, shutter speed will be irrelevant so I would set to max sync speed, 1/160th in my case, and then play with aperture until I get a correct exposure ?? Is this a good place to start .. ?? Bearing in mind of course, I dont have an incidental flash/light meter ..

Whilst on the subject of incidental meters .. How exactly do they work ?? Im assuming that you hold the meter in front of to read the light falling onto the subject. Does the meter then indicate to you a correct shutter speed and aperture and you just set your camera and strobes accordingly ?? Is it a matter of just replicating the numbers ... ??

TOM

10-03-2009, 11:56pm

Leigh has explained this better than I. Just remember that with flash photography there are two seperate exposures happening. This is the key to getting to grips with flash. One is the flash/aperture/distance exposing the subject (usually in the foreground unless you are using snoot or barndoors - forget about his for now), and the second is the shutter speed/aperture/ambient/ light exposure - just as you would expose a shot without flash.

The background is not epxosed by distance as your last post suggests. With you black backdrop scenario, you are right. Shutter has little affect on this shot. I would tend to go for max sync to try to underexpose the black background. This is opposite to my earlier post where I would overexpose for a white background. it is not so much a matter of the flash overpowering the ambient, which it does do, but the speed in which the flsh works. the flash (very fast) determines the exposure along with the aperture and it doesn't matter about the shutter speed as it is ALWAYS going to be slower than the flash.

when using a meter, you will pre set your flash at a power setting. Let's say 1/16th power. Your flash is two meters from the model. You get the model to hold it in front of themselves, and you fire the flash. the meter will then indicate to you the correct aperture. It will not give you a shutter speed as it is not required. These meters are incident meters and will only measure the light falling on them. as the background is under differnet lighting (ambient rather than flash) and some distance away, it has no way of determining this. it is something you will want to choose youreslf depending on your desired effect.

bigdazzler

11-03-2009, 12:04am

ok yea i get the error with the distance/background thing .. now i read it back.

with the porttaits, in the absence of a flash meter, i would simply set SS to max sync and experiment with aperture/distance until the exposure looks good ??

was i right about how the meters work ?? Its been something ive been meaning to ask one of you more experienced flash guys.

EDIT: RE: The meters. I replied as you edited .. oops

bigdazzler

11-03-2009, 12:15am

.

when using a meter, you will pre set your flash at a power setting. Let's say 1/16th power. Your flash is two meters from the model. You get the model to hold it in front of themselves, and you fire the flash. the meter will then indicate to you the correct aperture. It will not give you a shutter speed as it is not required. These meters are incident meters and will only measure the light falling on them. as the background is under differnet lighting (ambient rather than flash) and some distance away, it has no way of determining this. it is something you will want to choose youreslf depending on your desired effect.

ok thanks mate, its something ive always wondered, how you determined your settings using an incidental meter. So its only aperture that gets determined by the meter .. ok.

So.. if i was setting up an outdoor portrait shot and had my flash 2 metres from the model, I would test fire at the model and determine the required aperture, and set my camera accordingly. Then to expose for the background, lets say a beach scene at dusk, I would meter a seperate exposure off the sky or whatever part of the scene, and then set my shutter speed corresponding to the predetermined aperture from the flash test shot ?? Now this would in theory give me an even exposure and maintain ambient light and detail in my background. But If I wanted to underexpose the background slightly, to create seperation of model from bg, I would set the shutter speed so that my meter indicated a 1 stop underexposure ?? Am I on the right track ??

TOM

11-03-2009, 12:19am

with the porttaits, in the absence of a flash meter, i would simply set SS to max sync and experiment with aperture/distance until the exposure looks good ??

difficult to answer. every situation is going to require evaluation and with time you will develop kind of like a fifth sense. you will intuitively know where to set your aperture and power. with digital, you have the ability to chimp. this is really going to be a task for you, not having the ability to manually adjust you power output. essential items for flash portraiture imho are at least one shoot through umbrella with stand. a decent softbox is going to be too limiting with the small power of a speedlight. if you look at the catchlight in my image above, you will see that this was taken with a flash and a bounce card. this type of catchlight is not very attractive.

edit: you snuck a post in on me. yes to get some nice seperation, I like to go about two stops under. This also applies to ttl flash as well, which you should use manual in - meter the scene, adjust your you meter displays about two stops under, and then fire. during the a daytime outdoor portraite session, you are going to be wanting fill flash - this is different again.

bigdazzler

11-03-2009, 12:29am

with digital, you have the ability to chimp. this is really going to be a task for you, not having the ability to manually adjust you power output. essential items for flash portraiture imho are at least one shoot through umbrella with stand. .

ok well i have a shoot through brolly and stand so at least i now have a starting point where ill be able to have a play and see what i can come up with .. yea the limitations of my flash wont help me i guess. thats what i was getting at when i said before that my only real option is to set to max sync and then manipulate aperture until I can maybe get something that looks ok .. i took these (http://www.ausphotography.net.au/forum/showthread.php?t=23775&highlight=bella) with a shoot through brolly and my speedlight off camera .. difference here is i was triggering with the onboard flash. The light is soft enough, but broad and flat and has no shape .. thats the whole reason i bought the triggers., to see if i could improve these kinds of shots by not having to use the onboard flash as a tirgger.

TOM

11-03-2009, 12:37am

yeah sure, but the max sync speed is not important, just don't go above it. more than likely you will be well below it. your choices are to adjust the aperture or the distance of the brolly. if you could get the brolly in really close, and wind down the power output of the flash (if required), you will get some nice wrap. Then another flash at the rear with a snoot to add a nice bit of backlighting on the hair........

All the best with your flash experimenting and be sure to post some samples along the way. If you get the chance, do pick up a nice little cheap flash unit ($100) and then you can really start experimenting.

bigdazzler

11-03-2009, 12:40am

ok thanks mate, its something ive always wondered, how you determined your settings using an incidental meter. So its only aperture that gets determined by the meter .. ok.

So.. if i was setting up an outdoor portrait shot and had my flash 2 metres from the model, I would test fire at the model and determine the required aperture, and set my camera accordingly. Then to expose for the background, lets say a beach scene at dusk, I would meter a seperate exposure off the sky or whatever part of the scene, and then set my shutter speed corresponding to the predetermined aperture from the flash test shot ?? Now this would in theory give me an even exposure and maintain ambient light and detail in my background. But If I wanted to underexpose the background slightly, to create seperation of model from bg, I would set the shutter speed so that my meter indicated a 1 stop underexposure ?? Am I on the right track ??

I dont want this ^^^^^^ to get lost in the thread before it gets answered. Would this be the way to go about setting up and exposing for this kinda shot ??

TEITZY

11-03-2009, 10:27am

^^^^ Sounds fine Darren. In these situations you will possibly need to use a shutter speed higher than the fastest flash sync speed (to expose the BG correctly) unless your aperture is quite small.

Cheers
Leigh

bigdazzler

11-03-2009, 12:40pm

ok thanks guys .. the info and help is much appreciated. Now that i got my head around this concept a little I might head on over to ebay and find a cheap manual flash to play with .. i guess all i need is a unit with manual power and a sync input .. brand is irrelevant yea ??

TOM

11-03-2009, 1:47pm

brand is irrelevant. as TEITZY explained above, you could use your camera in high sync special mode but i am not sure if that is available off camera. the other option, which will allow for greater controlof dof, is to use one, or a combination of nd filters to get your shutter below sync. using high speed sync comes at the detriment of power.

TEITZY

19-03-2009, 2:54pm

TOM, I assume the camera hot shoe adapter is similar to a PC cord connection (rather than TTL) which should allow Darren to flash sync at any speed. You can do this with Nikon speedlights/bodies that don't have FP Sync mode by simply taping over the outer (smaller) contacts on the camera hotshoe and just leaving the main centre contact exposed.

Cheers
Leigh

TOM

19-03-2009, 4:46pm

Tietzy, I don't understand your post. Are you saying that flash sync is irrelevant with the Nikon's under certain circtumstances other than FP?

JM Tran

19-03-2009, 5:56pm

wow I cant believe Sony is allowed to get away with selling a flash unit with no Manual control for flash power output!

in a studio shoot with backdrop, shutter speed has very little effect, but is much more evident when shot indoors or outdoors with a subject - the slower the shutter speed, the more ambient light is drawn in and gives the background a more natural look.

TEITZY

19-03-2009, 10:32pm

Tietzy, I don't understand your post. Are you saying that flash sync is irrelevant with the Nikon's under certain circtumstances other than FP?

No just saying you can fool the camera into thinking there is no flash connected. You can do this with PC cord as well but obvously you have to use the flash in full manual mode. This normally works pretty well up to 1/1000 on most Nikon bodies but is a bit more problematic on the Canons in terms of shutter blackout. Here are some D70s shots using the SB800 in the hot shoe with the contacts taped at 1/1000, 1/2500 & 1/8000 :eek:

Cheers
Leigh