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DPChallenge Forums >> Hardware and Software >> can the 420ex overexpose
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 05/30/2005 02:31:37 PM · #1
A question for the tech gurus.

I have a Canon 420ex running off my Digital Rebel. What I would like to know is if I can deliberately overexpose with this flash/camera setup (i.e. create brilliant white backgrounds for while having my subject properly lit). Here is an example of what I mean. I have tried everything that comes to mind, but the flash always gives a "green light" (properly exposed flashed image) and I don't get that brillinat white background.

Do I need to invest in a 550ex to achieve the kind of result I'm looking for? Can the Digital Rebel do this kind of image with a speedlite?
 05/30/2005 02:36:05 PM · #2
Thats not over exposing. thats using a pure white base and back drop with some nice lighting in probably 2 or 3 maybe more spots.

//www.kohscamera.com/multibl.htm

Message edited by author 2005-05-30 14:37:15.
 05/30/2005 02:37:38 PM · #3
If you're using the hack I believe you have flash exposure compensation available. Otherwise you could try shooting in manual mode with the flash and deliberately overexpose or Move in closer than the flash range and shoot from there.
 05/30/2005 03:42:54 PM · #4
Think about it: you're using a Speedlight on-camera to light your scene. This means that both your subject and your background are being lit by the same light source. Not only that, but because the source is on the camera, it follows night must the day that your subject is gonna recive more light than your background, since by definition it's closer to the light source.

So, we have a problem. Sure, you can "overexpose" to turn the background pure white if you set the camera manually, but however much you overexpose the background, you're overexposing the subject by even more, since it's closer ΓΆ€” net gain, zero.

Your solution is to light the background and subject separately, and you can't do that with only on-camera flash. Period. You can slave a tripod-mounted strobe that is lighting the BG only off your camera-mounted flash, but even so the on-camera flash is a horrible way to light stuff anyhow, even if it's convenient, 'cuz there's NO modelling of surface or texture or volume possible with that setup.

Robt.
 05/30/2005 04:22:39 PM · #5
Originally posted by dpakoh:
Thats not over exposing. thats using a pure white base and back drop with some nice lighting in probably 2 or 3 maybe more spots.

//www.kohscamera.com/multibl.htm


Nah. You don't need a fancy get up like you mention for the beer bottle shot in my first post. That was done with 20D, 550EX with omnibounce and camera set to +2 E/V.
 05/30/2005 04:24:11 PM · #6
Originally posted by bear_music:
Think about it: you're using a Speedlight on-camera to light your scene. This means that both your subject and your background are being lit by the same light source. Not only that, but because the source is on the camera, it follows night must the day that your subject is gonna recive more light than your background, since by definition it's closer to the light source.

So, we have a problem. Sure, you can "overexpose" to turn the background pure white if you set the camera manually, but however much you overexpose the background, you're overexposing the subject by even more, since it's closer ΓΆ€” net gain, zero.

Your solution is to light the background and subject separately, and you can't do that with only on-camera flash. Period. You can slave a tripod-mounted strobe that is lighting the BG only off your camera-mounted flash, but even so the on-camera flash is a horrible way to light stuff anyhow, even if it's convenient, 'cuz there's NO modelling of surface or texture or volume possible with that setup.

Robt.


Same answer as above. Jacko used the 550EX on camera to achieve the result. Got it from the horse's mouth.
 05/30/2005 04:24:48 PM · #7
Originally posted by Beagleboy:
Originally posted by dpakoh:
Thats not over exposing. thats using a pure white base and back drop with some nice lighting in probably 2 or 3 maybe more spots.

//www.kohscamera.com/multibl.htm


Nah. You don't need a fancy get up like you mention for the beer bottle shot in my first post. That was done with 20D, 550EX with omnibounce and camera set to +2 E/V.


Well there ya have it; if you're gonna BOUNCE flash, just use manual or compensate +2 for the white?

R.

addendum: one was presuming direct illumination of the subject/BG in one's exegisis...

Message edited by author 2005-05-30 16:25:51.
 05/30/2005 04:32:56 PM · #8


That was done with 2 60W Bulbs and a Canon Powershot A40, so it won't cost you much. I know there's an exposure compensation setting for flash on the 350D so I'm sure there's one on the 300D as well. Good luck getting that white background, best bet is to use a white sheet or even a really big, bent piece of cardboard...

g'luck!
 05/30/2005 04:34:04 PM · #9
Originally posted by AlexMonty:


That was done with 2 60W Bulbs and a Canon Powershot A40, so it won't cost you much. I know there's an exposure compensation setting for flash on the 350D so I'm sure there's one on the 300D as well. Good luck getting that white background, best bet is to use a white sheet or even a really big, bent piece of cardboard...

g'luck!

actually there isn't without the hacked firmware.
 05/30/2005 04:39:17 PM · #10
Oh!? They should at the very least have an 'endorsed' firmware upgrade for the 300D with that feature included...if not then they're just being ridiculous.
 05/30/2005 04:45:21 PM · #11
Originally posted by AlexMonty:
Oh!? They should at the very least have an 'endorsed' firmware upgrade for the 300D with that feature included...if not then they're just being ridiculous.


It's called m-a-r-k-e-t-i-n-g. They probably had the function already when the 300D came out, but decided to hold out until the release of the 350XT before including it. That way they can "make us" replace our cameras faster. They're evil, evil I tell ya!

I will most likely be installing the hack as soon as the warranty expires on the camera.

Man, I just the saw the 350XT for the first time in person on Saturday. It's puny. I really find they made it too small.
 05/30/2005 05:45:45 PM · #12
I don't think you can manually expose with the 420EX. Even in manual mode, it automatically tries exposing it correctly (but usually under by 1 stop. For a poorly lit "concert" (poor excuse for a concert, IMO), I set my my camera for it's widest aperture, 1/60th of a second, ISO 400, and had the flash on to provide the remaining needed light apart from ambient. It exposed well, meaning it didn't go at full power, which if it had, would've ruined the pictures with harsh light and shadows.
 05/30/2005 07:36:35 PM · #13
I was using a 70-200 f2.8L with a 420EX with Sto fen diffusers outside as a fill in flash and I kept getting really overblown shots, even turning down FEC to -2 didn't solve it. Couldn't figure it out. I then shot indoor and it was fine right afterwards. Haven't used the flash again yet, so I can't tell if this is a common thing.
As for your picture, it may be a bit overexposed, but it doesn't seem too extreme as mine was. Mine was almost all white.
 05/30/2005 07:44:58 PM · #14
Originally posted by yido:
I was using a 70-200 f2.8L with a 420EX with Sto fen diffusers outside as a fill in flash and I kept getting really overblown shots, even turning down FEC to -2 didn't solve it. Couldn't figure it out. I then shot indoor and it was fine right afterwards. Haven't used the flash again yet, so I can't tell if this is a common thing.
As for your picture, it may be a bit overexposed, but it doesn't seem too extreme as mine was. Mine was almost all white.


The problem here is that the flash sync is only 1/200 when you need something faster. Ontop of that you're adding more light! Not a good idea! The second you turn the flash off you camera can go back to 1/2000 or 1/3200 or anything it needs. 1/200 is many stops more light than that.
 05/30/2005 09:12:38 PM · #15
I think their is a high speed syn feature on the 420EX for flash using shutter spped greater than 1/200. If so would that have helped? Sometimes even in plenty of light you need a fill flash to get rid of the harsh shadows under the eyes, which was what I was trying to do. Perhaps the 420EX was too powerful and I could have used the pop up flash on the camera itself. Another photog was with me with a 20D and a 580EX and she was getting very good exposure with a Canon 75-300. So I'm not sure if there was too much light or if the E-TTL was being fooled or something.

Message edited by author 2005-05-30 21:17:40.
 05/30/2005 09:28:24 PM · #16
I don't know anything about a high speed sync so I cannot help you there. I do know my camera won't do faster than 1/200 with a flash on.
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