How Do i solve this - DPChallenge Forums

04/27/2004 01:25:33 PM · #1

I hhave Canon a40 which was not meant to be used with external flash but i use two powerful studio strobes with help of digital peanut slave.

Problem i am facing currently is that When i try to mask inbuilt camera flash ( which fires digital slave) with help of a visiting card i grossly underexpose mt shot,of course everyone will say it has to happend as i am removing source of light, true but Practically speaking how should absence of a small inbuilt compact flash have such big impact of causing such gross under exposing .

Sample A was taken without masking inbuilt flash. Sample A

Sample B was taken with masking inbuilt flash.
Sample B

There is abig difference between A and B.

I have noticed when i choose macro mode depite using inbuilt flash there is difference in exposure, my camera tends to underexpose.

My take is that inbuilt camera flash has preflash and when i mask flash than there is under exposing,
When i have to subjects like above it is fine but when i have to shoot close up and that too off highly reflective subjcet that i need to mask the flash.
So what do i do

04/28/2004 01:17:03 AM · #2

Anyone Who can help me

scottwilson

Canon EOS-350D Rebel XT

Canon EF 28mm f/2.8

04/28/2004 01:29:24 AM · #3

I think you may well be right on the pre-flash trigering the
studio strobes.

Some cameras will allow you to turn off the pre-flash.

Canon EF 100mm f/2.8 USM Macro

04/28/2004 01:46:13 AM · #4

sadly i cannot turn off the pre flash

Spork99

OM System OM-1

04/28/2004 03:12:59 AM · #5

time for a camera upgrade

Canon EF 70-200mm f/2.8L IS USM

04/28/2004 04:54:29 AM · #6

Ya you are right.
I just want to know do camera that offer use of external flash also tend to underexpose when using a macro function

Jovi

Sony DSC-F717

04/28/2004 08:42:31 AM · #7

You can fix incorrectly exposed photos with PS most of the time.

I know its a tad overexposed, just a quick example on what you can do with PS.

EddyG

Canon EOS-1D Mark II

04/28/2004 09:05:17 AM · #8

Not sure if it will help or not, but Digi-Slave flashes are specially designed to work with digital cameras that fire pre-flashes. They are "programmable" and "learn" the pre-flash sequence for your camera, and then only fire the "real" flash when appropriate.

Not sure if there would be a way to get the on-camera flash to fire only the Digi-Slave (whose light output would then fire the studio strobes) without triggering the studio strobes in the first place, but just thought I'd mention it. Seems like you might be able to rig something up so only the Digi-Slave saw the on-camera flash but the studio strobes didn't (but would see the flash from the Digi-Slave).

Originally posted by General:

I have noticed when i choose macro mode depite using inbuilt flash there is difference in exposure, my camera tends to underexpose.

Since you are in macro mode, I assume you are photographing something very small and close-up. Often times the built-in flash doesn't work very well in these situations because the flash is off-axis from the lens, and this causes the lens itself to cast a shadow on the subject. That is one reason they make macro ring lights: so the light is as on-axis with the lens as possible for even illumination.

Message edited by author 2004-04-28 09:08:24.

Spork99

OM System OM-1

Canon EF 100mm f/2.8 USM Macro

04/28/2004 09:51:27 AM · #9

Originally posted by EddyG:

Not sure if there would be a way to get the on-camera flash to fire only the Digi-Slave (whose light output would then fire the studio strobes) without triggering the studio strobes in the first place, but just thought I'd mention it. Seems like you might be able to rig something up so only the Digi-Slave saw the on-camera flash but the studio strobes didn't (but would see the flash from the Digi-Slave).

Try putting a sheet (or sheets) of white paper over the on camera flash. It will significantly reduce the output of the on camera flash, but still create enough light to trigger the slave.

Nikon AF-S DX Zoom-Nikkor 18-55mm f/3.5-5.6G VR

04/29/2004 12:06:39 AM · #10

digital peanut slave i use ignores the pre flash but the problem is when i try to cover the flash with paper ( reason for covering flash is that sometimes i click reflective subjects ) Camera under exposes , I tried covering the flash in Sample B.

I guess it is time to upgrade my camera

mykoleary

Nikon D3300

05/01/2004 02:07:12 AM · #11

I've actually found that in some instances, (even with JUST the built in flash) that using a couple pieces of Scotch tape over the flash help cut down the harshness of it tremendously.

Experiment with different kinds of tape, and then keep a couple pieces of those rolls that worked out best on a sticker page in your bag so that you can carry them and reuse them when you need to...

ClubJuggle

Canon EOS-400D Rebel XTi

Canon EF 28-135mm f/3.5-5.6 IS USM

05/01/2004 08:45:33 AM · #12

If I understand this correctly, it sounds like you are using the camera in auto. When shooting with strobes, you really should be choosing the exposure settings manually.

-Terry

Canon EF 28-135mm f/3.5-5.6 IS USM

05/01/2004 09:05:53 AM · #13

Well thanks for the input but i feel i could not explain my problem clearly.I will try again

I shoot in manual mode. I have camera that doesnot allow me to use external flash , It has a pre flash, i use two studio strobes using a digital peanut slave. This slave ignores preflash and fires on main flash.

Now what i have noticed lately is that if i cover my inbuilt camera flash with visiting card (in order to bounce the flash to peanu slave)in order to avoid direct flash my pictures come out under exposed. Eg is Sample B Sample B

If i dont mask my camera flash results are like Sample A

It is some times necessary to mask inbuilt camera flash if i have to shoot higly reflective subjects

dr rick

Canon EOS-300D Rebel

05/01/2004 09:52:52 AM · #14

I can see why you want to cover the built-in flash! To get the right exposure, open your aperture a stop. If that would lower the DOF too much, you'll need to make the strobes brighter, either by an adjustment on the strobes or by moving them closer. If all else fails, the underexposure isn't too serious, so it is feasible to correct in your digital darkroom.

The strobes have a different white balance than the built-in flash; they are quite a bit warmer. That makes the resulting photo look a bit darker.