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Archive 2012 · Mixing Ambient and Strobe
  
 
RyanGphoto
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p.1 #1 · p.1 #1 · Mixing Ambient and Strobe


So I wasn't sure where to post so this was the best bet.

I shoot a lot in studio and there i have no issues with exposure (my trusty Sekonic 358 helps). However when I head outside I have major issues and I am sure it's technical.

I check my subject under a shady area. Exposure is say 1/160th, ISO200, F13 in the shade. I then power up the strobe and get a meter reading of 1/160th, ISO200, F13 at 50%.

When I take the shot at 50% my subject is totally dark. I figured they would be pretty close to properly exposed in the shade, but nope. I have to drop down to almost F8, F9 to get the subject REALLY close to proper exposure.

What am I missing / doing wrong here?

Thanks
Ryan G

p.s. Here are three shots showing what I mean. First without strobe, then strobe on shot at F13, then at F9

Strobe Test Issues



Nov 19, 2012 at 10:55 PM
Jay Connor
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p.1 #2 · p.1 #2 · Mixing Ambient and Strobe


vidioprof

Can you tell me what you mean by the " 50% " part of the exposure

Do you mean 1/160th, iso 200, at F13.5

Jay



Nov 19, 2012 at 11:08 PM
RustyBug
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p.1 #3 · p.1 #3 · Mixing Ambient and Strobe


Sunny 16 would suggest that ISO 200 would be 1/200 @ f16. A meter reading of 1/160 f13 is only 1 stop more exposure.

My rough rule of thumb for moving from sun to shade (without metering) is 2 1/2 stops diff. The fact that you are metering ambient in shade @ only a 1 stop diff makes me wondering if your metering technique is giving you a false reading.

F8 is two stops opened up from Sunny 16, so that would seem reasonably close to what I would expect without a meter ... the flash making up the difference of the missing 1/2 stop or so when shooting f8/f9

I suspect that your meter technique (incident dome I assume) is fibbing to you. Try recessing your dome so as to not gather as much ambient. Also, what mode do you have your meter in, i.e. ambient, flash or flash + ambient when you take your meter reading. Also, is it possible that you've got your meter in reflective mode rather than incident mode when you've changed from ambient metering to flash metering (been there done that)?

While I'm not precisely sure where the issue is ... I'm pretty sure that 1/160, f13 is a definite underexposure for shade @ only 1 stop more exposure than Sunny 16 (note background exposure @ f13). As such, I'd review metering technique first.

BTW, what flash unit / modifier @ what distance from subject?




Nov 19, 2012 at 11:24 PM
Gregg Heckler
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p.1 #4 · p.1 #4 · Mixing Ambient and Strobe


I'm assuming you have your camera set on "Manual" exposure to start?

So you are saying the ambient reading is 1/160 at f/13 taken at the subject? This f/stop seems a little small for shade. I'm guessing you really mean the back ground reading is this. Your ambient reading on the models face is probably more like f/5.6 or 8. So if you are cutting your strobe power by 50% then that's probably why it's so under-exposed. But there are many variables you are leaving out like strobe power, modifiers, distance of strobe to model, etc. Remember yo control your ambient light (background) with the shutter speed and your model's exposure via your f/stop and strobe setting.



Nov 20, 2012 at 05:57 AM
BrianO
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p.1 #5 · p.1 #5 · Mixing Ambient and Strobe


vidoprof wrote:
...Here are three shots showing what I mean. First without strobe, then strobe on shot at F13, then at F9


The first two have properly exposed backgrounds, but an underexposed subject. The third shot has a properly exposed subject, but an overexposed background.

Here's what I would do:

Using the camera's meter in averaging mode, set the exposure to give a proper background exposure. (Subject not in the frame.)

Next, use your flash meter to set the strobe's output to give the same exposure at the subject location.

Bring in your subject and take your shot. Where the strobe light falls, the subject will be exposed normally, and where the strobe doesn't hit, the subject will be shaded (lit by ambient only). Positioning the strobe will allow you to chose the type of highlight/shadow modeling -- butterfly, short lit, broad lit, etc.

You can then adjust the strobe's output and/or the shutter speed to vary the precise ratio of strobe to ambient, but going equal is a good starting point.



Nov 20, 2012 at 06:17 AM
RustyBug
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p.1 #6 · p.1 #6 · Mixing Ambient and Strobe


+1 @ Brian's process of ambient, then strobe. Even without a meter the process is effective with Sunny 16 ROT.

BrianO wrote:
Using the camera's meter in averaging mode, set the exposure to give a proper background exposure. (Subject not in the frame.)


Sunny 16 @ background @ ISO 200 is 1/200 @ f16

Next, use your flash meter to set the strobe's output to give the same exposure at the subject location.

Subject in shade (no flash) @ same 1/200 would require f6.3 (2 1/2 stops diff), thus a need for fill light to raise the subject to match the background. If your strobe/modifier output has an effective GN @ ISO 200 of say 160 ft (easy math), then light placement would be GN160 / f16 = 10ft from subject to attain a proper exposure for the subject.

You can then adjust the strobe's output and/or the shutter speed to vary the precise ratio of strobe to ambient, but going equal is a good starting point.

As Brian also noted, your last exposure was overexposed for the background, as one would expect if you had an aperture / shutter @ f9 & 1/160. This is why you determine your ambient background exposure first and add fill to the subject based on the necessary f-stop for the background.

Brian is correct that you can adjust your shutter/aperture combination, but the camera's sync speed can be a limiting factor that restricts you from opening up your aperture very much and still retaining a proper exposure for your background with an offsetting shutter adjustment. As such, the overexposed background is a common occurrence if you open up the aperture too much.

As to balance of strobe & ambient, Brian mentions that equal is a good starting point. I agree that it makes for the easiest calculation / starting point. My preference is to have my strobe slightly under @ -2/3 or so, such that it doesn't have quite as strong of a "strobe" look.

The salient point being made here is that ambient is based on aperture and shutter, whereas flash is based on aperture and flash to subject distance (for a given GN/power output), with shutter being of little consequence except for sync limitations.

From that, we can realize that the common lynchpin connecting the two is the aperture. The fine tuning of ambient exposure is via shutter, the fine tuning of strobe exposure is via power/distance.



But ... I'm still wondering how you got a 1/160, f13 exposure reading in the shade

I'm also wondering if the fact that you got the SAME reading with your flash @ 50% means that you are NOT adding any (significant) flash to the subject. This could be the case if you are metering in flash+ambient mode.

Based on what you've said your readings were, I'm inclined to think that your meter was in reflective metering mode (seeing all the light behind the camera) and/or ambient+flash mode (getting the bulk of its light from ambient) when you took your flash reading.



Nov 20, 2012 at 01:45 PM
onetrack
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p.1 #7 · p.1 #7 · Mixing Ambient and Strobe


vidoprof wrote:
So I wasn't sure where to post so this was the best bet.

I shoot a lot in studio and there i have no issues with exposure (my trusty Sekonic 358 helps). However when I head outside I have major issues and I am sure it's technical.

I check my subject under a shady area. Exposure is say 1/160th, ISO200, F13 in the shade. I then power up the strobe and get a meter reading of 1/160th, ISO200, F13 at 50%.

When I take the shot at 50% my subject is totally dark. I figured they would be pretty close to
...Show more

First, let's assume that your meter is working properly. If you meter with it towards the flash, dome out, and it reads 50%, then that means that 50% of the proper exposure (reading) is due to the flash. Ambient is whatever is left.

But, that only accounts for light coming from the general direction of the flash. It does not know how much back light you have.

So, if you are in a high ambient light environment, first, put your meter in ambient light mode and meter behind your subject towards the sun. If it reads f13 at your selected ISO & shutter speed, then you know that if you want to have the background darker than your subject, you're going to need more than f13 from the flash and ambient light falling on your subject from the front.

You can experiment to get a better feel from there. You might even need more than one flash in front depending upon the situation.



Nov 20, 2012 at 04:13 PM
jefferies1
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p.1 #8 · p.1 #8 · Mixing Ambient and Strobe


I don't think I have ever got a reading close to what you list in the shade. Even in Texas where the sun is way too bright. My shade shoots will be around ISO 100-200, F5 and maybe 125 sec or less. Usually slower than that as I bring a tripod with me due to the slower shutter required. I really never want to go over F5.6 and use F5 as my go to for portraits.

For me F13 and 150 would be a bright sun photo, not shade.

In ETTL I would dial down the flash to -1/3 or -1/2 so it is only filling in where required. Adds light to the eyes but no flash look. Always have camera in Manual or it will do whatever it wants and with bright backgrounds will not be correct. I alo use flash in manual just because it is easier for me to fine tune.

If you are trying to brighten the shade so you equal the bright background then that is another issue. You need much more than fill light for that.



Nov 21, 2012 at 12:21 AM
hugowolf
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p.1 #9 · p.1 #9 · Mixing Ambient and Strobe


vidoprof wrote:
I check my subject under a shady area. Exposure is say 1/160th, ISO200, F13 in the shade. I then power up the strobe and get a meter reading of 1/160th, ISO200, F13 at 50%.

When I take the shot at 50% my subject is totally dark. I figured they would be pretty close to properly exposed in the shade, but nope. I have to drop down to almost F8, F9 to get the subject REALLY close to proper exposure.

More questions than answers, but when you say "Exposure is say 1/160th, ISO200, F13 in the shade", how are you metering this? Is it with the camera's reflective metering or with the Sekonic using incident metering?

Brian A



Nov 21, 2012 at 02:22 AM
RyanGphoto
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p.1 #10 · p.1 #10 · Mixing Ambient and Strobe


Jay Connor wrote:
vidioprof

Can you tell me what you mean by the " 50% " part of the exposure

Do you mean 1/160th, iso 200, at F13.5

Jay



The meter reading says how much of the exposure is flash.. ON a Sekonic L-358 it's in the top right hand corner..

Ryan G



Nov 23, 2012 at 08:52 PM
 

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RyanGphoto
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p.1 #11 · p.1 #11 · Mixing Ambient and Strobe


RustyBug wrote:
Sunny 16 would suggest that ISO 200 would be 1/200 @ f16. A meter reading of 1/160 f13 is only 1 stop more exposure.

My rough rule of thumb for moving from sun to shade (without metering) is 2 1/2 stops diff. The fact that you are metering ambient in shade @ only a 1 stop diff makes me wondering if your metering technique is giving you a false reading.


It's certainly the thing I think is going on... I like that 2.5 stops difference "rule" thanks

F8 is two stops opened up from Sunny 16, so that would seem reasonably close to what I would expect without a meter ... the flash making up the difference of the missing 1/2 stop or so when shooting f8/f9

I suspect that your meter technique (incident dome I assume) is fibbing to you.


I have the dome extended on a Sekonic 358 when taking the reading in shade which my model's entire body is in the shade

Try recessing your dome so as to not gather as much ambient. Also, what mode do you have your meter in, i.e. ambient, flash or flash + ambient when you take your meter reading.

Always use the Flash reading but it gives me the amount of light the flash is giving me as a % of the entire scene... so something like 1/160th F13 ISO200 50% I'll have to try recessing the dome

Also, is it possible that you've got your meter in reflective mode rather than incident mode when you've changed from ambient metering to flash metering (been there done that)?

Don't know .. I guess I have to look that up cause I just set it to the SUN (ambient) and then back to the Lightning bolt (flash).. and take my readings

While I'm not precisely sure where the issue is ... I'm pretty sure that 1/160, f13 is a definite underexposure for shade @ only 1 stop more exposure than Sunny 16 (note background exposure @ f13). As such, I'd review metering technique first.

BTW, what flash unit / modifier @ what distance from subject?


I am using a Broncolor Grafit A2 with a P90 reflector. Distance is about 20ft (sometimes 15).. Could that be it?





Nov 23, 2012 at 09:14 PM
RyanGphoto
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p.1 #12 · p.1 #12 · Mixing Ambient and Strobe


Gregg Heckler wrote:
I'm assuming you have your camera set on "Manual" exposure to start?

So you are saying the ambient reading is 1/160 at f/13 taken at the subject? This f/stop seems a little small for shade. I'm guessing you really mean the back ground reading is this. Your ambient reading on the models face is probably more like f/5.6 or 8. So if you are cutting your strobe power by 50% then that's probably why it's so under-exposed. But there are many variables you are leaving out like strobe power, modifiers, distance of strobe to model, etc. Remember yo control
...Show more

Yes set on manual and taken where the subject would be standing that would be the meter reading. That IS ISO200. I really don't know the background reading as I was shooting over the water so I didn't actually take a reading out there.. But I would assume it would have been ISO200 F16, 1/320th.

I was just taking a meter reading in the shade to give me an idea of what that said. I didn't cut the strobe power really. I set the strobe on X power output and it gave me a reading of 50% ambient and flash so I though that would make sense. I am guessing not now.

I totally get the shutter controls (for the most part) ambient and Aperture control flash power (for the most part).

I didn't and don't think the strobe power and modifiers and distance (maybe) matter if I am getting a meter reading from the strobe. Meaning.. If I have 20 strobes with 20 different modifiers I understand I will get different reading from them depending on the modifier and strobe power and distance... however If I have all those strobes at the same distance with the same output I will most likely get the same meter reading (depending on the type of modifiers), but here I am using the same modifier so none of those things should matter.. Right?

Ryan G



Nov 23, 2012 at 09:28 PM
RyanGphoto
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p.1 #13 · p.1 #13 · Mixing Ambient and Strobe


BrianO wrote:
The first two have properly exposed backgrounds, but an underexposed subject. The third shot has a properly exposed subject, but an overexposed background.

Here's what I would do:

Using the camera's meter in averaging mode, set the exposure to give a proper background exposure. (Subject not in the frame.)

Next, use your flash meter to set the strobe's output to give the same exposure at the subject location.

Bring in your subject and take your shot. Where the strobe light falls, the subject will be exposed normally, and where the strobe doesn't hit, the subject will be shaded (lit by ambient only). Positioning the
...Show more

Brian.. I think that is what I was TRYING to do with the 50% reading from the Sekonic, but maybe (definitely?) my technique is off.. Studio not problem cause there is no ambient in there, but outside.. trouble.

Do I use the meter to get me the same exposure as the shaded area at 100% flash on the meter? This is hard to explain.. My meter tells me a % of flash vs ambient it "sees". Do I make that 100% of the light hitting the meter is the flash output?

Thanks to everyone for all the help.

Ryan G




Nov 23, 2012 at 09:33 PM
RyanGphoto
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p.1 #14 · p.1 #14 · Mixing Ambient and Strobe


RustyBug wrote:
+1 @ Brian's process of ambient, then strobe. Even without a meter the process is effective with Sunny 16 ROT.

Sunny 16 @ background @ ISO 200 is 1/200 @ f16

Subject in shade (no flash) @ same 1/200 would require f6.3 (2 1/2 stops diff), thus a need for fill light to raise the subject to match the background. If your strobe/modifier output has an effective GN @ ISO 200 of say 160 ft (easy math), then light placement would be GN160 / f16 = 10ft from subject to attain a proper exposure for the subject.

As Brian also noted, your last
...Show more

Thank you so much for this explanation and playing off of Brian's comments as well. This makes a lot of sense. It could be that I did exactly that and had the meter in Flash + Ambient mode. I will have to check next time i go out.

I shoot a lot over the ocean or lakes here for the nice background and sky and yes I notice that dropping my aperture down to F9 blows out the sky and I can't really increase my shutter much because my sync speed is 1/200th (it says 1/250th, but i notice a tiny black line at that, but none at 1/200th so i stay there). My old 1DIII was 1/320th and 1/400th was obtainable sometimes with a tiny bit of a line, so I was saving a stop there and cutting the sky down.. now I can't really do that, but maybe I will drop the ISO or use an ND filter to cut the sky and not have to use as much flash power so I can get faster recycle times on my vagabond.

I will have to try this, but thanks for the tips.

Ryan G




Nov 23, 2012 at 09:41 PM
RyanGphoto
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p.1 #15 · p.1 #15 · Mixing Ambient and Strobe


jefferies1 wrote:
I don't think I have ever got a reading close to what you list in the shade. Even in Texas where the sun is way too bright. My shade shoots will be around ISO 100-200, F5 and maybe 125 sec or less. Usually slower than that as I bring a tripod with me due to the slower shutter required. I really never want to go over F5.6 and use F5 as my go to for portraits.

For me F13 and 150 would be a bright sun photo, not shade.

In ETTL I would dial down the flash to -1/3 or
...Show more

Thanks (I am in FL so I kinda know what you mean about the brightness).. I could have had the meter in the wrong mode I suppose, but it is now definitely more of a technique thing. I just need to bring the flash in more (but it's harder for groups as the spread is less (so maybe use a different modifier too).. I wasn't and don't use flashguns but usually packs and heads or monolights when shoting so I do have the power but it's the recycle time i want to keep down if i can so I want to use less power when I can.

Thanks for the comments.

Ryan G



Nov 23, 2012 at 09:46 PM
RyanGphoto
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p.1 #16 · p.1 #16 · Mixing Ambient and Strobe


hugowolf wrote:
More questions than answers, but when you say "Exposure is say 1/160th, ISO200, F13 in the shade", how are you metering this? Is it with the camera's reflective metering or with the Sekonic using incident metering?

Brian A


I am using the Sekonic 358 using the last mode to the right (lightning bolt). I actually never use the camera meter (maybe I should) to get exposure when using a strobe in the shot.




Nov 23, 2012 at 09:48 PM
BrianO
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p.1 #17 · p.1 #17 · Mixing Ambient and Strobe


vidoprof wrote:
...I actually never use the camera meter (maybe I should) to get exposure when using a strobe in the shot.


It can be helpful in getting the background exposure correct, and then you adjust the strobe exposure (using the flash meter) to the camera's settings. Then you can change the BG exposure up or down a little using shutter speed, to suit your taste for BG:subject ratio. (If that puts you over sync speed, then you adjust the strobe output instead.)



Nov 24, 2012 at 05:55 AM
Steve-Adoria
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p.1 #18 · p.1 #18 · Mixing Ambient and Strobe


I have the same meter, but as my Phottix Odin radio triggers always do a pre-flash I don't actually use the meter in flash mode.

What I find seems to work fairly consistently is meter according to the backgound (no subject in scene) in relective mode - not with the white dome. Camera on manual. Set the ISO the same on the camera and meter, set the F Stop on the camera and meter according to the depth of field required (in this case f/3.5 to get lots of background blur), then take a meter reading, pointing the meter towards the brightest part of the background to get the speed setting and set up the camera with those settings.

I then use flash purely to pop some light on the subject, eliminate harsh shadows, and brighten the eyes with nice catchlights etc. The initial meter settings usually get you close to ideal. Take a test shot or two to make fine adjustments.
I'm sure there are better ways of doing this... I've only really made the transition from natural light to strobist hack this year, so I'm still learning this too.

In this photo taken last weekend, it was a very sunny mid-afternoon late spring here in Sydney. We are shooting the subjects standing in shade to get them out of the harsher ambient light.
ISO 200 /3.5 1/500 sec; Lighting was via two speedlights (ex580ii & ex430ii ) mounted in a Kacey Beauty Dish triggered via Phottix Odin in TTL mode using High Speed Synch. I believe TTL compesation was dialled back a little (-0.3).


Daddy's Home! by adoriaphotography, on Flickr

Here is another one taken on the same day, but I don't think the lighting was quite so good. It was taken just after midday so the ambient lighting was challenging. Also, being a larger group taken with a 70-200mm lens from afar, the beauty dish had to be a fair way back to be out of frame, so the light was a bit flat compare to the first image. I'm still very happy with the results though given the conditions we had to work with.
ISO100 F/3.5 1/500s (same two speedlights in beauty dish triggered by Phottix Odin with HSS enabled)


family portrait by adoriaphotography, on Flickr

Edited on Nov 30, 2012 at 05:24 AM · View previous versions



Nov 26, 2012 at 12:44 AM
Steve-Adoria
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p.1 #19 · p.1 #19 · Mixing Ambient and Strobe


Ryan, in response to your PM, I have updated the previous post - the images are now on Flickr as my regular web site is down (expired SSL certificate)

Something else I have noticed just now is that the three images you have on dropbox, EXIF data is available on the images when in full screen mode.
For all three images the exif data is showing that the flash did not fire.
I'm guessing that if the flash had actually fired for one of the first two images, the results would be pretty good.

Cheers, Steve



Nov 30, 2012 at 05:17 AM
tedwca
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p.1 #20 · p.1 #20 · Mixing Ambient and Strobe


Steve, he is using bron color strobes, the exif info won't know anything about them firing. At least if I'm reading the posts correctly. ;-)


Nov 30, 2012 at 07:54 AM





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