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10/07/2005 02:08:42 PM · #1 |
I have got Canon S2 IS Digital Camera. I wanted to enhance the flash power, so I went in for a Slave Flash. Following has been experienced:
1. In Auto mode, the images appear to be under exposed when the additional flash is used. This is in comparison with the shot taken by buit in flash alone. I mean to say that the Slave flash works negatively. Had the shot taken with the help of Slave Flash been overexposd, it would have been normal. Why this anomalous behaviour ?????
2. When the slave flash is used in manual shooting mode, it behaves normally.
3. What is the problem? Does the problem lie in camera, flash or in me?
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10/07/2005 02:12:06 PM · #2 |
Originally posted by saharsh:
I have got Canon S2 IS Digital Camera. I wanted to enhance the flash power, so I went in for a Slave Flash. Following has been experienced:
1. In Auto mode, the images appear to be under exposed when the additional flash is used. This is in comparison with the shot taken by buit in flash alone. I mean to say that the Slave flash works negatively. Had the shot taken with the help of Slave Flash been overexposd, it would have been normal. Why this anomalous behaviour ?????
2. When the slave flash is used in manual shooting mode, it behaves normally.
3. What is the problem? Does the problem lie in camera, flash or in me?
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What brand/model of flash are you using?
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10/07/2005 02:17:30 PM · #3 |
I am using Vivatar 3200 flash, mounted on a vivitar SL2 Slave unit with hot shoe. i have tried taking exposures in thyrister mode, as well as manual mode on this flash, but the problem persists. Moreover I must add that Canon S2 IS does not have pre-flash phenomenon.
Thanks, |
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10/07/2005 02:18:16 PM · #4 |
| Post the pictures and provide some EXIF details. |
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10/07/2005 02:46:00 PM · #5 |
Hi Saharsh. I also have an S2 and I also have an external flash. I have a Tumax DS20S2. I don't think the S2 in that name is related the S2 in any way. It is a generic model designed for recent digital cameras.
Digital cameras used to have a single preflash that was used to set a couple of things before the picture was taken, most particularly to get an idea of the reflectivity of the scene for metering and flash durations etc. Recently, Canon Digitals and some others have been adding multiple preflashes.
After experimenting with my flash unit and reading the manual about a month and a half ago, I discovered that the Canon S2 fires multiple preflashes in Auto, P, Av, and Tv modes as well as the special shooting modes. In manual mode, you can set the function of the flash to manual (or it is automatically set as such, I kinda forget and it's nearly 3am) and it will not fire the preflashes - in this mode ONLY. This requires you to set the flash strength which is available in the menu.
When your pictures come out underexposed, it means that your oncam flash fires a burst, which triggers the slave flash. The camera sees the light from the slave flash as part of it's preflash bounceback for scene appraisal. The high light levels received at this time tell the camera that the scene is both well-lit and highly reflective, hence it turns down the power of the illumination burst. When the on-cam flash fires its actual illumination burst, the slave flash is spent and because the camera has set the main illumination burst down a lot, you end up with an underexposed picture.
This is the way it works. You need to find out if your vivitar has additional settings. Otherwise, see if you can return it and find a place to buy the Tumax. It's a pretty decent unit that comes with a mounting plate and even has a tiltable head. It can be used for just about any kind of Digital Camera and even has a cable sync which does not have any use with the S2. It has three flash power settings including manual and two thyristor settings and has a distance/aperture chart on the back. It can be test fired manually.
Hope it's what you are looking for. You might consider re-reading your manual. I always do when I come against a wall I thought I understood, but can't quite seem to negotiate. I have re-read my manual 4 times and still pick up little tidbits each time that I either forgot or missed.
Admittedly, I still can't figure out how to slice bits off the movie clips in camera. |
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10/08/2005 01:19:06 AM · #6 |
P 159 of the S2 manual gives information regarding the Canon Slave flash. It says that in M mode, it will not fire. This is because Canon only programmed their flash to work with the multiple-preflashes which are in all modes EXCEPT M mode.
P 105 shows you how to turn off what are called Flash Adjustments (these are the evaluative pre-flash bursts) that fire before the illumination burst. This can only be done in Av and Tv modes. In the menu, you can turn the flash adjustments from auto to manual.
******* This change will allow you to use your slave flash in those modes as well because it will behave the same as in manual. The only problem is that things get a lot tricker when you are manualling adjusting your flash power. I usually set my flash power down a fair bit and let the slave do most of the work. This makes less work for me when juggling two primary light sources as one light source will become less important, and the one you can play with more (your off-camera slave) will be far more simple to work with. I would recommend shooting in Av mode and keeping between F3.2 and 4.5 for the majority of your shots. That is where the lens on the S2 seems to work best.
If I need to go to F8, I'd rather see what I could do with an ND filter due to the diffraction limitations of the S2. |
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10/08/2005 01:26:57 AM · #7 |
Hi Eschelar,
Thanks a lot. You have really solved my problem. Now I can shoot with my slave flash in Manual mode, and in Tv and Pv modes, with manual flash settings.
Thanks again. |
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10/09/2005 11:29:05 AM · #8 |
I'm not so sure that you can use P. Just M, Av and Tv.
I'd still go back to the store and look around for something. It is much more difficult to get good lighting using the manual flash settings. The camera does A LOT of things with the information from the preflashes.
Also, once you get going with it, make sure you take a hundred or two shots with different methods of using flash. Try to set your camera in Manual mode so there are as few variables as possible. Most importantly, learn about the optimal distance from the subject in a manual flash mode. You will need to be reasonably familiar with that as soon as you start using the flash in real world situations.
Another thing that might be useful is to find a way of securing the flash to a tripod so you can make a mobile setup to really make use of the more powerful external flash unit. This is really useful with portraits. |
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