Problem with Flash Photography


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mattimpat

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Apr 28, 2005
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Hi, I'm new to SLR photography and have just started with a Chinon CP-7m. I have taken some pictures with a roll of Kodak Royal Supra 400, most of which have come out OK, but I am having trouble shooting indoor pictures with a dedicated flash. I used a 50mm lens and bounced the flash off the ceiling. I used F8 aperture (as the manual reccommended) and let the camera choose the shutter speed. The results were very grainy and I can't understand why. Please help, one of the photos is below:



The film was near its use-by-date, but I thought that just affected the colour. Could it be something to do with the lighting? If you'd like to see more photos, just ask.

Matthew
 

jovedaddy

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hi Matthew. first of all, welcome to Clubsnap :)
since you mentioned that only the indoor flash pics came out grainy, i would think that the indoor pics are all underexposed. the photo-labs will usually try to correct the underexposure for you during printing, but the result would be "grainy" pictures.
try studying your flash and camera again and see how you can overcome the underexposure (i believe shooting at a wider aperture eg. f4.5 and/or increasing the flash power should help) :)
 

Witness

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its probably due to underexposure,,,resulting in more grain/noise when processing it back to the normal exposure...

cheers....
 

mattimpat

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Thanks for your advice, I'll try changing the aperture next time. As I was using the camera to select the shutter speed shouldn't that have sorted ou the exposure? Could it be that the glass on the picture frame was throwing off the meter by reflecting a lot of light?

I have heard that the meter tries to achieve middle grey. The picture below seems darker than middle grey to me and I took it in program mode (hence it should have been overexposed), and it is also slightly grainy. However there is a lot of metal and glass. Can these things throw off a meter reading?

Thanks,

PS: If I change the aperture won't the camera adjust the shutter speed so that the exposure stays the same (unless I used manual mode, of course)?
 

Ashleyy

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rough example for flash.. u need to check yr flash for exact specs...

At ISO 400, 1/125, 50mm, direct flash:

F8 - might be up to distance of 5m
F4 - up to 8m
F2.8 - up to 16m...

above numbers given as example only, not the actual values..
lowering yr aperture should help. definitely the shutter speed will be affected when u adjust the aperture..

Also for bounce flash photography.. if your shuttle speed is too fast, the shutter might already be closed before the light can travel from the flash to the ceiling, down to subject &/or background and back to the camera...

For your 2nd pic, anything that reflects a lot of light can mess up the metering.. try to meter on another spot... Some examples of incorrect metering: mirror, glass, water reflections, etc
 

varf

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mattimpat said:
Thanks for your advice, I'll try changing the aperture next time. As I was using the camera to select the shutter speed shouldn't that have sorted ou the exposure? Could it be that the glass on the picture frame was throwing off the meter by reflecting a lot of light?

I have heard that the meter tries to achieve middle grey. The picture below seems darker than middle grey to me and I took it in program mode (hence it should have been overexposed), and it is also slightly grainy. However there is a lot of metal and glass. Can these things throw off a meter reading?
your camera's meter will (usually) try to achieve middle gray, but middle gray may not give an exposure which is ideal to you. reading the following article might help:

http://luminous-landscape.com/tutorials/understanding-series/understandexposure.shtml

mattimpat said:
PS: If I change the aperture won't the camera adjust the shutter speed so that the exposure stays the same (unless I used manual mode, of course)?
in aperture-priority or program-shift (or similar) modes, yes. but flash exposure is a dark art. :devil:

the effectiveness of your flash is mainly related to aperture + ISO speed. the peak output for your flash may be insufficient for the selected combination of aperture, ISO speed and subject distance, especially when using bounce flash, but personally i don't think that's the case here.

i am not an expert, but what i think is likely is that the ISO400 film you are using is grainy to begin with, and you shouldn't expect noise-free prints from the film.


Ashleyy said:
Also for bounce flash photography.. if your shuttle speed is too fast, the shutter might already be closed before the light can travel from the flash to the ceiling, down to subject &/or background and back to the camera...
this is incorrect, light travels much faster than your shutter is capable of moving. :bsmilie:
this article explains the problem with flash and fast shutter speeds better than i can:

http://www.kenrockwell.com/tech/syncspeed.htm#why

hope that helps.
 

reno77

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#8
For Indoor flash you can set the camera on manual to 1/60 f5.6.. this is kind of a default setting. You can go lower up to 1/15secs if you're shooting in a dimly lit wedding hall.
 

Ashleyy

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varf said:
this is incorrect, light travels much faster than your shutter is capable of moving. :bsmilie:
this article explains the problem with flash and fast shutter speeds better than i can:

hope that helps.
Mmm.. u r rite to say that light travels faster than a camera's shutter speed.... but what I am refering to here is more on the sync speed of the flash and shutter....

If the flash fire before the shutter is open... flash might be over b4 the shutter is open or ending when the shutter is opening... either case can result in under-exposure...

Same thing happens when the flash fire too late when the shutter is closing or already closed...

The ideal is the flash fire and provide sufficient power after the shutter open and before the shutter close...

Y do u think camera's got a sync speed of 1/125, 1/200, 1/250 shutter speed? It's not because light travel slower than the shutter speed but time taken for the camera to trigger the flash and stop the flash for TTL metering...
 

dkw

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#10
Ashleyy said:
Mmm.. u r rite to say that light travels faster than a camera's shutter speed.... but what I am refering to here is more on the sync speed of the flash and shutter....

If the flash fire before the shutter is open... flash might be over b4 the shutter is open or ending when the shutter is opening... either case can result in under-exposure...

Same thing happens when the flash fire too late when the shutter is closing or already closed...

The ideal is the flash fire and provide sufficient power after the shutter open and before the shutter close...

Y do u think camera's got a sync speed of 1/125, 1/200, 1/250 shutter speed? It's not because light travel slower than the shutter speed but time taken for the camera to trigger the flash and stop the flash for TTL metering...
Sorry Ashleyy, your concepts are totally mixed-up. Sync speed has absolutely nothing to do with the time it takes a camera to trigger or stop a flash or even TTL metering. TTL metering occurs BEFORE the shutter is open and is no way interferes with shutter operation. In fact, the way SLRs are built, you couldn't meter if the mirror was lifted and shutter open. Also, a flash pulse is typically waayyyy shorter than shutter speed. For an SLR camera, at faster than sync speed, the second curtain starts to close before the first curtain has moved fully across the frame. That's ok for routine photography, but if you trigger a flash pulse at faster than sync speed, what you will get is an illuminated slit. The exception here is high-speed sync, which paradoxically prolongs the flash pulse. Please read the link that varf has provided, for a better idea about sync speed.

Cheers,
 

Ashleyy

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dkw said:
Sorry Ashleyy, your concepts are totally mixed-up. Sync speed has absolutely nothing to do with the time it takes a camera to trigger or stop a flash or even TTL metering. TTL metering occurs BEFORE the shutter is open and is no way interferes with shutter operation. In fact, the way SLRs are built, you couldn't meter if the mirror was lifted and shutter open. Also, a flash pulse is typically waayyyy shorter than shutter speed. For an SLR camera, at faster than sync speed, the second curtain starts to close before the first curtain has moved fully across the frame. That's ok for routine photography, but if you trigger a flash pulse at faster than sync speed, what you will get is an illuminated slit. The exception here is high-speed sync, which paradoxically prolongs the flash pulse. Please read the link that varf has provided, for a better idea about sync speed.

Cheers,

Okie okie.. guess i din explain properly.. sorry... ;p
 

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