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Archive 2011 · General Flash Question.
  
 
Billingham
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p.1 #1 · General Flash Question.


Taking a group shot, two rows of people, 14 in all. Indoors, not the best light.
5D with EX580, mounted on tripod. camera set to AV, F8, ISO 400. ETTL flash set to +1 FEC bounced off ceilling.
Lighting looks okay but shots grainy and a little soft.A little noise reduction and sharpening has made them acceptable but know I could do a lot better.
Any pointers to help me improve would be apprieciated

Regards
Jonathan



Dec 22, 2011 at 01:47 PM
cgardner
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p.1 #2 · General Flash Question.


Sounds like you did the best you could under the circumstances but just didn't have enough flash power. In ETTL mode you never know for sure what % of total flash power was used, except via the recycle time, but I suspect that at + 1 FEC it was already firing at full power.

Suggestions for doing things differently would be to bring a ladder to raise camera and flash above the group then use direct flash rather than bouncing and you will have more power and will be able to used a lower ISO. The higher vantage point with the faces looking up will also result in a more flattering look to the faces, from above, with the necks stretched creating an "instant facelift" effect that eliminates the double chins and nostrils seen in a lower level tripod shot.

What I do when I need a tall tripod is attach my ball head to a board with a counter-sunk 1/4"-20 bolt then clamp the board to the top of my 7' step ladder...












Also in a situation like that I'd suggest using M mode on the flash. Starting at 1/1 power will tell you immediately whether or not you have enough power for that ISO or not, allowing you to raise it if needed, or lower it if possible to reduce the noise.

For group shots using two flashes will double the amount of output. What I do is put my slave on below my shooting position just in front of the ladder about chin level with the subjects like this...









Dec 22, 2011 at 02:08 PM
Billingham
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p.1 #3 · General Flash Question.


Great info, gives me some thing to work on. Thanks.
Merry christmas



Dec 22, 2011 at 02:27 PM
jefferies1
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p.1 #4 · General Flash Question.


A photo would be helpful. You could have grain from under exposure. Sometimes it would be better to up the ISO for better exposure and a cleaner image in print. Forget the Auto flash and AV mode as you have no control. Set camera and flash to Manual mode and try to lock the exposure in at a good F stop you have selected.Maybe start at F5.6 and if well exposed move to F8. Several ways to do it. More flash power, a larger flash source like using a unprella for more spread, higher ISO. If you have room light then a slower shutter will capture more of the ambiant light, within reason. A 1/50 shutter will have a lot more room light than a 125sec. For 2 rows I would want around F8 depending on the depth of the rows and length of lens used. F8 will be safe most of the time.

Your soft shots would be from movement, lack of depth of field( one person/row sharp, those in back soft depending on what row you focused on) or not using the spot focus. If allowing the camera to pick the focus point which would most likely not be eyes or face which is what needs to be in focus everyone will appear soft.



Dec 22, 2011 at 09:24 PM
BrianO
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p.1 #5 · General Flash Question.


Billingham wrote:
...camera set to AV, F8, ISO 400. ETTL flash set to +1 FEC bounced off ceilling. ...Lighting looks okay but shots grainy and a little soft.


What was the shutter speed? Why did you choose +1 FEC? How big was the room, and how high was the ceiling? What color was the ceiling?

Answers will help in getting accurate advice, and as mentioned posting a sample shot will help a lot if you're able.



Dec 22, 2011 at 10:18 PM
 

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Billingham
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p.1 #6 · General Flash Question.


Thanks for your help guys.
Happy holiday's



Dec 23, 2011 at 09:14 AM
RustyBug
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p.1 #7 · General Flash Question.


jefferies1 wrote:
Sometimes it would be better to up the ISO for better exposure and a cleaner image.


+1 High ISO gets a rap for noise, but underexposing a lower ISO (imo) can be a worse rap than a proper exposure/ISO combination even if the ISO is a little higher than you'd want for a "fine art" image. You really weren't flirting much with "high ISO" ... one more stop could have made a bit of difference. High(er) ISO with enough light is better than low ISO with too little light ... your 5D can easily handle ISO 800.

+1 @ BrianO ceiling height, etc. The GN of your flash (for a given ISO, and given AOV) is for your flash to subject distance. While your camera to subject distance is a straight line, your flash to subject bounced off the ceiling is going to be a longer light path.

There are three things that seem to be working against you on this.

1. Longer light path of the bounce (reduces aperture calculated from a given GN)
2. Wide beam setting for group coverage (reduces GN)
3. Bounce absorption/diffusion (reduces effective GN) +1 FEC assumed as attempt to account for this

While the 580 EX has a rated GN of 58m (at 105mm FL coverage), it is rated @ 36m for a 35mm FL coverage

http://speedlights.net/compare-speedlight-specs/?model=580EX&model2=580EX+II
http://gdlp01.c-wss.com/gds/3/0300004013/01/speedlite580exii-en-es-fr.pdf

You didn't say what FL coverage you were using, camera to subject distance or ceiling height, so I'll make some assumptions to illustrate.

At ISO 100, a GN of (appx) 100 ft (35mm zoom head setting) and a camera to subject distance of 12 feet, your aperture should be f8. (i.e. 100 / 12 = 8.5)

Take that same camera/subject distance and bounce your flash off a 12 foot high ceiling and your distance increases by a factor of 1.4 ... so now, instead of GN 100 / 12 ft = f8, it becomes GN100 / 17ft = f5.6

While you can tell your flash to add in +1 FEC, it can't add in more than it is capable of producing. So, even though you've told it to compensate for the loss caused by the bounce difusion loss (in addition to the extra distance), the amount of light available to do so isn't really increased because we are calculating from MAXIMUM to begin with ... so we still have to somehow account for that loss ... which takes us down from 5.6 to 4.0.

So, at MAX POWER the 580EX will deliver correct exposure for a camera to subject distance of 12 feet, with 12 foot high (assumed white) ceilings, with the flash set to a 35mm FL coverage will yield an aperture of roughly f4.

However, if your shooting distance is farther than 12 feet, or your flash zoom head setting is even wider than 35mm (or both) your effective GN / respective aperture will be even lower. I'm guessing that you may have been farther away than 12 feet for a group of 7 people wide and were using your flash's zoom head at wider than 35mm setting ... thus lowering your GN below the 36m we started from, suggesting that f2.8 (or f2.0) is probably more likely the appropriate aperture at ISO 100.

Obviously an aperture of 2.8 would seem to shallow of a DOF for your group, so the increase of 2 stops from ISO 100 to ISO 400 gains you an effective aperture of 5.6. Shooting at f8 would then be a 1 stop underexposure ... and your attempt to compensate using the +1 FEC is a good thought ... but you've already exhausted all the light your flash has to offer ... so even though you are asking it to compensate for the bounce loss ... it simply can't make up the difference if it doesn't have anything left to do so with. If f5.6 is where you want to be, ISO 400 is all the "higher" you need to go. But if you are wanting to shoot f8 or f11, you'll need to be at ISO 800 or 1600 unless you make other changes.

Solutions:

1. Raise ISO to 800 and gain that stop
2. Move flash off camera, closer to subject or closer to ceiling (or both) to reduce light to subject distance
3. Position group in 3 rows or arc to allow for a narrower FL for lighting coverage
4. Set your flash zoom head to a longer FL setting (it is traveling farther via the bounce and will disperse wider than if it were aimed directly at subject)
5. Add more light (i.e. second flash, increase ambient)

After all that ... it simply sounds like you were underexposed because your flash was "maxed out" from being asked to spread a "wide beam" ... a "long way" ... off a "soft/textured/diffuse surface". Bounce has a nice effect regarding your "quality" of light ... but it does come at a price to be paid regarding the "quantity" of light reaching your subject.

HTH

NOTE: While unlikely for this type of shot (i.e. future reference) ... it is also possible that somehow your camera's metering (mode ??) picked up a strong specular reflection that trigger the flash to power down some. (Another good reason for shooting manual.)

Also, while the "calculations" are theorectical, many digital cameras ISO ratings are slightly inflated from reality by 1/4-1/5 stop as they are "rounded up" to the standard ISO increments, i.e. ISO 400 might only be ISO 360 or so ... not really a biggie for most situations, but when you are already short on light, it doesn't help matters any either.



Edited on Dec 24, 2011 at 03:21 PM · View previous versions



Dec 23, 2011 at 01:24 PM
xtremediver
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p.1 #8 · General Flash Question.


Here is a very good book to read that really explains shooting with both camera and flash on manual and controlling your light (very simply).
"Studio Lighting Unplugged" by Rod and Robin Deutschmann.
You can purchase through Amherst Media and I am certain from other locations, too.
Inside or outdoors, this really explains manual flash very well and gives you lessons to try for immediate understanding of what you are doing.



Dec 23, 2011 at 01:26 PM
Billingham
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p.1 #9 · General Flash Question.


Rustbug; Thanks for such a comprehensive reply. After reading your response, several times, i totally get where you are comming from. Thanks for taking the the time to explain where and what i need to do to improve.
Xtremediver; Thanks for the book recommendation. I have a couple of books about flash photographay but alas they are not aimed at the beginner. Shall order the above and hopefully move forward.

This is why I joined FM. Great people that are always willing to pass on their knowledge and experience. Thanks again guys



Dec 23, 2011 at 09:42 PM
RustyBug
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p.1 #10 · General Flash Question.


Jonathon ... Thanks and you're welcome.

I'm glad that you "get" it ... always a "coin toss" when I try to explain things.




Dec 24, 2011 at 03:18 PM





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