help please-Blinking - not allowing 800 shutter speed

[Chilli]

hello and sorry if this is such a dumb question.
I was trying to shoot a flame, (mid afternoon and indoors)
using my 50d canon with 70-200mm at f2.8
i wanted a shutter speed of around 800 as i was trying to capture
the flame in action and yet blurr all the background. my camera would not allow this setting, it kept blinking the "no can do".
I tried all settings, manual, av, tv and the only way i could shoot was with a very slow shutter speed.
I also tried moving ISO up and down from 100 up to 1250 (just for curiosity sake) and still could not shoot at these settings.
What am i doing wrong ?

[maccaroneski]

This may be totally on the wrong track, but is your camera set to focus priority? i.e. do you need to have focus for the shutter to act?

[Chilli]

hi,
do you mean if the shutter speed works with manual focus or auto focus mode?

[ricktas]

my guess, the camera could not auto focus on the scene, and therefore it will not let you take the shot if you have AF on, single. Try manual focusing

[etherial]

This sounds a little strange to me. With the 7D (I imagine the 50D is the same???) the only thing that will make the shutter speed or apperature value flash is if you are in Av or Tv and the camera is out of range. Ie if you are trying to set the shutter at 1/800 while in Tv and the cameras metering says it needs a very large apperature that is bigger than it is able to open to the F4.0 (or whatever the maximum apperature is) will flash. Or similarly if you are shooting at a really bright light in Av with the apperature wide open, it will flash 1/8000 (or whatever the fastest shutter speed is) telling you that it even at this fast speed it thinks the shot will be overexposed.

The indicator for failed focus is a green dot on the right hand corner that flashes.

So that doesn't really answer your question, but that is the normal behaviour for the 7D and as far as I can remember the 450D I had previous.

I would think given the above it is probably more related to exposure than focus. One thing is flash, did you have any flash enabled because without high speen sync it wouldn't want to go over 1/250?

I'm not sure what else to suggest! Maybe post an image or two with EXIF that might help narrow down what it is doing?

[arthurking83]

flash? Either on board or external.. was it set to expose with flash?

[draco]

i am no expert but the 40D also does this when it cannot focus on the scene. have you tried going a bit further from the subject?

[bigdazzler]

As etherial says, your SS or Aperture numbers will usually only flash like that in the semi-manual modes if the chosen shutter speed/aperture cannot match the other to meter and achieve a correct exposure.

I think your camera is trying to achieve an impossible exposure.

Im trying to picture your scene, and indoors by firelight, im thinking that even at 2.8 you wont be able to achieve 1/800th. Upping your ISO should fix that though.

Try sticking your camera in Av, move back and zoom to as long as you can go to compose your scene how you want it, open up your lens to 2.8, and take note of the shutter speed youre getting. If its not up near where you want, pump the ISO until you get as close as you can.

As for catching the flame in "action" ... You should know that 1/800th will actually freeze that flame solid, if youre after some flicker or movement you will need to use a slower SS.

Dont forget to report back !!

[Chilli]

Hi and thankyou to everyone above.
Darren yes I did try uping the ISO with no luck, and yes i realised myself after posting that the slow ss will capture the flame and NOT the 800..
Am on my way out now and I will re try it all again later today and report back.
Thanks for all the help guys....

[ving]

my guess... turn the flash off. flash wont sync at 1/800th (?)

just a guess.

there is no reason it wouldnt AF on a flame.

[bigdazzler]

spot on Ving .. Flash certainly wont sync at that speed, but unless Im missing something the OP didnt mention the flash being popped up/firing. If it was, that certainly could be the problem.

I dont think its AF either .. it should be able to detect a contrasting edge somewhere.

[maccaroneski]

I dont think its AF either .. it should be able to detect a contrasting edge somewhere.

I was thinking more along the lines that if AF wasn't on continuous servo, then with the flickering it would lose it pretty quickly - maybe too quick for the shutter to fire after having achieved focus.

[ving]

s but unless Im missing something the OP didnt mention the flash being popped up/firing. If it was, that certainly could be the problem.

which means the camerea was not in manual, aperture or shutter priority modes and some sort of auto mode (i dont have a canon, they might not have manual mode).


i doubt there would be enough movement in the flame to make focus hard, continuous servo or not. :/

[Chilli]

Hi and thanks again for your assistance. Please disregard the composition etc of these pics.
They are straight out of camera purely for purpose of understanding.
Here are 3 out of many pics I took. No flash. Yes I was in manual or av or tv at one time or another.

[etherial]

Looking at the exif on the first one for example:
1/8 second
F3.2
ISO 250

If you want to get the same exposure on this frame but with a shutter speed of 1/800 you would need an ISO of 25600 which your camera is not capable of. As you have seen with these shots a much slower shutter is required for this scene. Setting the aperture wide open at F2.8 the fastest shutter you will get in this scene is 1/125 at ISO3200 or 1/250 if you can push to ISO6400.

Does that make sense?

[Chilli]

Yes it makes sense. Thankyou.

[ving]

soooo.... in short what you need to do to get the shutter speed you are after is increase ambient light.

[bigdazzler]

Looking at the exif on the first one for example:
1/8 second
F3.2
ISO 250

Darren yes I did try uping the ISO with no luck

There is no reason why your SS shouldnt increase if you pumped your ISO.

If you pumped your ISO to even ISO1600 ... thats 2 and 2/3rd stops. That increase should have seen your SS go to around 1/50th.

I dont see why you SS didnt increase when you bumped your ISO, like you said.

[Chilli]

There is no reason why your SS shouldnt increase if you pumped your ISO.

If you pumped your ISO to even ISO1600 ... thats 2 and 2/3rd stops. That increase should have seen your SS go to around 1/50th.

I dont see why you SS didnt increase when you bumped your ISO, like you said.

Hi, that's why i was asking the question ? I couldn't see either..