Approve the Cookies
This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies. Read More.
OK
Index  •   • New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
Register to forums    Log in

 
FORUMS General Gear Talk Flash and Studio Lighting
Thread started 01 Feb 2009 (Sunday) 20:44
Prev/next
sponsored links
(this ad will go away when you log in as registered member)

Question on flash metering

 
sito
Senior Member
sito's Avatar
419 posts
Joined Jun 2005
USA
Feb 01, 2009 20:44 |  #1

Today I was playing around with several flashes and my Sekonic lightmeter L-358 and a question popped out. First I set my camera at ISO 200, f/8 and 1/60. Then I set my main light at 45 degree towards the subject and set its power until the flashmeter read f/8. Then I set the fill light. I adjusted its power until the Sekonic read f/5.6 (1 f/stop lower than the main light). After setting both lights, I took a reading of the two lights combined and the Sekonic read f/8 plus 7/10 (approximately that is f/10). To get a real f/8 with a shot of the two flashes combined, I needed to dial down the power of the two lights until I got an f/8 on the Sekonic. I think this is normal, for I have a DVD by Sekonic where there is a photographer stating the same effect.

However, I do not really understand why shooting two lights (one of which is underpowered) gives me more power than the main light. I would appreciate if anyone could explain that to me.


20D - 10-22mm - 17-85mm - 50 f/1.4 - 70-200 f/2.8L IS - 100mm Macro - 1.4x II - 420EX - Canon 550EX

LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as registered member)
TMR ­ Design
Cream of the Crop
TMR Design's Avatar
23,881 posts
Joined Feb 2006
Huntington Station, NY
Feb 01, 2009 21:02 |  #2

Think about it. Even though you're adding less light with the fill at 1 full stop lower than the main, aren't you still adding light? You can't add light and not see an increase in light, thus a smaller aperture reading on the meter. The fact that you are seeing 7/10 stop additional represents the small contribution to the exposure, but a contribution nonetheless.


Please call me Robert or Rob, not TMR
Gear List & Feedback | The Lighting Academyexternal link
"Art is the elimination of the unnecessary." - Pablo Picasso

LOG IN TO REPLY
johnz
Senior Member
johnz's Avatar
529 posts
Joined Sep 2006
Tampere, Finland
Feb 02, 2009 04:58 |  #3

I was playing with a light meter also this weekend, and faced some issues questions too.

In this example, aren't you still supposed to keep your camera at f/8 if you are looking for a correct exposure on the subject + some rim light? ( If that was what the OP was trying to achieve ).


- Tuomas Gustafsson
My smugmugexternal link - ( still on the works )
My gear list/ DOF calculator for Nokia phones
With Canon you can... spend all your money on glass.

LOG IN TO REPLY
bohdank
Cream of the Crop
bohdank's Avatar
14,060 posts
Joined Jan 2008
Montreal, Canada
Feb 02, 2009 06:59 |  #4

If the second light overlaps the coverage area of the main light, you are adding to the light.


Bohdan - I may be, and probably am, completely wrong.
Gear List

Montreal Concert, Event and Portrait Photographerexternal link
Flickrexternal link

LOG IN TO REPLY
Wilt
Wilt is an old fart who has extensive experience with many brands and many formats of cameras, and extensive lighting knowledge of both studio lighting and speedlights
Wilt's Avatar
35,756 posts
Gallery: 1 photo
Joined Aug 2005
Belmont, CA
Feb 02, 2009 10:16 |  #5

Light is like water...add more water, the bucket fills higher -- even when the flow rate from the smaller hose is a lot less than the main hose!

What most amateurs do not fundamentally understand is that if you were in a darkened room and opened the shutter (Bulb) and popped the flash 1 time, vs. 2 times, vs 4 times, vs. 8 times, vs 16 times, you are exposing the sensor/film to accumulating light that results in an exposure of 0EV, +1EV, +2EV, +3EV, and +4EV respectively. That is why the overall exposure is +0.7EV from your 1/60 f/8 single light reading. Bohdank was 100% right with his comment.


You need to give me OK to edit your image and repost!
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention
Keep POTN alive and well with member support http://photography-on-the.net/forum/donate.p​hp

LOG IN TO REPLY
sito
THREAD ­ STARTER
Senior Member
sito's Avatar
419 posts
Joined Jun 2005
USA
Feb 02, 2009 10:26 |  #6

I am getting the point. Thanks a lot. Question now is: What is the recommended workflow of lighting setup? Should I set first the main, then fill, then dial down both lights to match the flashmeter?


20D - 10-22mm - 17-85mm - 50 f/1.4 - 70-200 f/2.8L IS - 100mm Macro - 1.4x II - 420EX - Canon 550EX

LOG IN TO REPLY
Wilt
Wilt is an old fart who has extensive experience with many brands and many formats of cameras, and extensive lighting knowledge of both studio lighting and speedlights
Wilt's Avatar
35,756 posts
Gallery: 1 photo
Joined Aug 2005
Belmont, CA
Feb 02, 2009 12:02 |  #7

Read just the main. Then read just the fill. Use the readings to establish the contrast ratio of the lighting.

Read both lights together, set the aperture of the lens to that value. Shoot.


You need to give me OK to edit your image and repost!
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention
Keep POTN alive and well with member support http://photography-on-the.net/forum/donate.p​hp

LOG IN TO REPLY
johnz
Senior Member
johnz's Avatar
529 posts
Joined Sep 2006
Tampere, Finland
Feb 02, 2009 15:17 |  #8

Nice! Thanks, somehow i was under the impression that the f/stop is adjusted by the main light. This makes actually much more sense.. :)


- Tuomas Gustafsson
My smugmugexternal link - ( still on the works )
My gear list/ DOF calculator for Nokia phones
With Canon you can... spend all your money on glass.

LOG IN TO REPLY
steveathome
Goldmember
steveathome's Avatar
2,174 posts
Joined Mar 2006
UK
Feb 02, 2009 15:53 |  #9

sito wrote in post #7237740external link
I am getting the point. Thanks a lot. Question now is: What is the recommended workflow of lighting setup? Should I set first the main, then fill, then dial down both lights to match the flashmeter?

johnz wrote in post #7239345external link
Nice! Thanks, somehow i was under the impression that the f/stop is adjusted by the main light. This makes actually much more sense.. :)



If you want to shoot at a specific aperture, then IMHO Sito's post is the way to go.

Once you have your ratio set up, reduce both strobes equally to the desired output/aperture, this will maintain the same ratio.
(ie if your final meter reading is 7/10 over, reduce both strobes by 7/10)
Having strobes with accurate incremental control is an advantage.


If you tend to use similar set-ups, you can set your key light at the required amount that you normally need to drop (in this case7/10) from the beginning.
This method will also assist, if your strobes do not have accurate incremental control.

Hope this makes sense.




LOG IN TO REPLY
PacAce
Cream of the Crop
PacAce's Avatar
26,806 posts
Joined Feb 2003
ABE, PA USA
Feb 02, 2009 16:18 |  #10

Or, you can just work the aperture values backwards. If you want the camera set to, say, f/8, and you want a 2:1 main-to-fill ratio, meter the main light for f/5.6 and 5/10 (or half a stop under f/8 ). Then meter the fill for f/4 and 5/10 (one and a half stop under f/8 ). The combined reading, assuming the main and fill overlap, will then be exactly f/8. :)


...Leo

LOG IN TO REPLY
steveathome
Goldmember
steveathome's Avatar
2,174 posts
Joined Mar 2006
UK
Feb 02, 2009 16:21 |  #11

Thats what I meant in my last paragraph, but just maybe didn't put it into English very well :o




LOG IN TO REPLY
Papa ­ Carlo
Senior Member
587 posts
Joined Jun 2008
Feb 03, 2009 06:59 |  #12
banned

Wilt wrote in post #7238358external link
Read just the main. Then read just the fill. Use the readings to establish the contrast ratio of the lighting.

Read both lights together, set the aperture of the lens to that value. Shoot.

You forgot to mention that only main or only fill shoud be read with the dome down and directed towards the light and the resulting light with the dome up and pointed towards the camera. In my case it often happens that final resulting reading is lower than the main light. For example Main F8 hair light F4.5 the result F5.6.




LOG IN TO REPLY
TMR ­ Design
Cream of the Crop
TMR Design's Avatar
23,881 posts
Joined Feb 2006
Huntington Station, NY
Feb 03, 2009 07:05 as a reply to Papa Carlo's post |  #13

Not everyone meters as you're describing. With digital there are many (myself included) that meter for the highlights and the taking aperture is derived by metering towards the main source of illumination and not the lens.

These is always great debate and discussion over this and I don't want to see this turn into that debate again but if you're metering for highlights as I described then what you're describing does not occur.


Please call me Robert or Rob, not TMR
Gear List & Feedback | The Lighting Academyexternal link
"Art is the elimination of the unnecessary." - Pablo Picasso

LOG IN TO REPLY
Papa ­ Carlo
Senior Member
587 posts
Joined Jun 2008
Feb 03, 2009 09:12 |  #14
banned

TMR Design wrote in post #7244190external link
Not everyone meters as you're describing. With digital there are many (myself included) that meter for the highlights and the taking aperture is derived by metering towards the main source of illumination and not the lens.

These is always great debate and discussion over this and I don't want to see this turn into that debate again but if you're metering for highlights as I described then what you're describing does not occur.

So i your case do you lower the hemisphere or not ?




LOG IN TO REPLY
TMR ­ Design
Cream of the Crop
TMR Design's Avatar
23,881 posts
Joined Feb 2006
Huntington Station, NY
Feb 03, 2009 09:17 as a reply to Papa Carlo's post |  #15

Hi Papa Carlo,

If I'm metering a single light source and no other strobes are firing I do not lower the dome. If I'm metering a light source and other lights are firing then I do lower the dome and will go as far as shielding the dome so as not to have contribution from those other sources. When I'm metering for my final taking aperture I have the dome raised.


Please call me Robert or Rob, not TMR
Gear List & Feedback | The Lighting Academyexternal link
"Art is the elimination of the unnecessary." - Pablo Picasso

LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as registered member)

1,484 views & 0 likes for this thread
Question on flash metering
FORUMS General Gear Talk Flash and Studio Lighting


Not a member yet? Click here to register to the forums.
Registered members get all the features: search, following threads, own gear list and ratings, likes, more forums, private messaging, thread follow, notifications, own gallery, settings, view hosted photos, own reviews and more...


AAA

Send feedback to staff    •   Jump to forum...    •   Rules    •   Index    •   New posts    •   RTAT    •   'Best of'    •   Gallery    •   Gear    •   Reviews    •   Polls

COOKIES DISCLAIMER: This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies. Privacy policy and cookie usage info.

POWERED BY AMASS 1.4version 1.4
made in Finland
by Pekka Saarinen
for photography-on-the.net
Spent 0.00217 for 4 database queries.
PAGE COMPLETED IN 0.02s
Latest registered member is CondoPlanet
565 guests, 482 members online
Simultaneous users record so far is 5577, that happened on Mar 02, 2016