Go Back   Steve's Digicams Forums > Digicam Help > Flash (External)

Reply
 
Thread Tools Search this Thread
Old Apr 24, 2005, 4:38 PM   #1
Junior Member
 
Join Date: Sep 2004
Posts: 14
Default

I have a sigma DG super and noticed that you can set aperture and iso on the flash in manual mode. now what exactly does this do? as far is i understand it aperture and iso should only be needed using TTL. what gives?

j
phong is offline   Reply With Quote
Sponsored Links
Old Apr 25, 2005, 10:27 AM   #2
Senior Member
 
KCan's Avatar
 
Join Date: Jul 2002
Posts: 1,625
Default

phong wrote:
Quote:
I have a sigma DG super and noticed that you can set aperture and iso on the flash in manual mode. now what exactly does this do? as far is i understand it aperture and iso should only be needed using TTL. what gives?

j
I don't have this flash, but it may refer to the "auto mode" meaning the flash will adjust it's output (by it's own on board sensor) to match an aperture and a ISO setting of the camera. In this case, there is no feedback from the flash to the camera.

In "manual" mode, you only need an output setting (full, ½, ¼ , etc …) which correspond to a GN (guide number), the aperture and ISO settings become meaningless for the flash itself. You manage to have a good exposition by calculating the relation GN-ISO-aperture for the camera settings.

KCan is offline   Reply With Quote
Old Apr 25, 2005, 10:03 PM   #3
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

KCan

The EF-500DG Super does not have an 'Auto' mode...



Phong

-> In manual mode adjusting the aperture will vary the distance scale which is quite handy if you don't want to derive this from the GN - Provided of course if you input the ISO correctly:
http://www.stevesforums.com/forums/v...01&forum_id=53

This can be done by just mounting the EF-500DG Super on the hot-shoe and the ISO from the camera is transfered automatically to the flash (you can always overide this setting manually as well from the flash without having to mount it on the camera)
You do not then need to know the power setting (full, ½, ¼...) when used in this manner :idea:
i.e. the flash output is thus proportional to the aperture setting (as indicated by the distance scale)
NHL is offline   Reply With Quote
Old Apr 25, 2005, 10:45 PM   #4
Senior Member
 
KCan's Avatar
 
Join Date: Jul 2002
Posts: 1,625
Default

NHL, good info

... I would call this "assisted" manual mode :G
KCan is offline   Reply With Quote
Old Apr 25, 2005, 10:52 PM   #5
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

KCan wrote:
Quote:
... I would call this "assisted" manual mode :G
Right - Problem is with all this computerized assistance I tend to forget the basic arithmetic -> and here's my kids using their cell phones to figure out the tips! :evil:
NHL is offline   Reply With Quote
Old Apr 26, 2005, 5:26 AM   #6
Junior Member
 
Join Date: Sep 2004
Posts: 14
Default

Thanks for the info, all makes sense now
phong is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 11:03 PM.