To 'P' or not to 'P'

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torque22

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Hi
I am doing some photography in P Mode.
I have a 400d with a 70-200 f4 lens (no IS) attached.
I also have a 580exII flash running in TTL mode.

taking pictures inside at night the camera sets itself up at f4 and 1/60s for the exposure.

The rule of thumb says to use the reciprical of the focal length for the shutter speed. I am using approx 80-105 on my pics. So including the crop factor I should have a min shutter speed of approx 1/160s.

Using the flash and changing the ISO speed to 800 have no effect.

So other than having to cart a tripod with me what is the answer? how do i get decent pics at the correct shutter speed.
 
Change it to S or shutter priority? You can set the shutter speed yourself, and the camera will chose an aperature (sp?) to suit.

Thats what I do anyway with my Nikon D80, not sure how Canon are set up, but I'd imagine it'd have a similar option?

HTH, or I have gotten the wrong end of the stick and told you something completely wron g :lol:
 
Av - you choose the aperture, camera works out the shutter speed
Tv - you choose the shutter speed - it picks the aperture
 
Its already at f4 which is the max for this lens, it can't get any wider.
 
Av - Aperture values
Tv - Time values

:nuts:
 
torque22 said:
Its already at f4 which is the max for this lens, it can't get any wider.
Click to expand...

then you need more light on the subject - hence the flash!
should be able to use Av and get the flashgun to work out what to do
(you can force the shutter to 1/200 using a custom function)
 
mmcp42 said:
then you need more light on the subject - hence the flash!
should be able to use Av and get the flashgun to work out what to do
(you can force the shutter to 1/200 using a custom function)
Click to expand...

Thanks mmcp42, I will give that a try. But assume (hope) that the flash will do this auto as i have not had time yet to read its instruction manual.
 
no. did not work. but i miss understood you.

I set the camera to Tv 1/200 and hoped that the flash would do its stuff.
if i use Av i set it to f4 max, and the exposure light flashes at me. I have to adjust the shutter to 1/8s to get it to stop flashing. thats even worse than in P mode.

can you explain the custom function to me
 
on the camera menu select custom functions
you want #3, sets fixed (1/200) for flash in Av mode
default is for the camera to decide

then see what happens

(that's how I solved a similar problem - others will be along to slap us both down!)
 
Hello Torque,

You are fine letting the camera use a 60th for the shutter speed. You are right about using the focal length as a shutter speed guide in normal shooting but it doesn't apply nearly so much with the flash.

If the flash is the the source of most of the light in the shot, you can afford almost any shutter speed as the duration of the "flash burst" is going to be in the region of 100ths of a second anyway. This works out the same as a higher shutter speed and gets rid of the camera movement.

If you're shooting in brigher light with the flash as fill in, then you need to worry about the shutter again.

Also, you don't need to factor in the crop sensor for focal length/shutter speed purposes. :)
 
Understandable mistake Matty :thumbs:

Av is a normal abbreviation for 'have' as in "I av one"

Tv is what we watch when not at the computer processing our fab Nikon shots

When I first picked up a Canon with these settings, I read it as...

"I av a tv" and was very disappointed I couldn't get Eastenders on it

These Canonites... :cuckoo::cuckoo::cuckoo:
 
mattyh said:
ah, it's a bit different to the Nikon, where they use:

A: Aperture Priority
S: Shutter Priority

I think Nikon makes more sense :p
Click to expand...
As do every other camera brand.
Just Canon trying to be elitist again .:shake::lol:
 
mmcp42 said:
on the camera menu select custom functions
you want #3, sets fixed (1/200) for flash in Av mode
default is for the camera to decide

then see what happens

(that's how I solved a similar problem - others will be along to slap us both down!)
Click to expand...

Thanks, I will try that, but not till tomorrow.
 
dazzajl said:
Hello Torque,

You are fine letting the camera use a 60th for the shutter speed. You are right about using the focal length as a shutter speed guide in normal shooting but it doesn't apply nearly so much with the flash.

If the flash is the the source of most of the light in the shot, you can afford almost any shutter speed as the duration of the "flash burst" is going to be in the region of 100ths of a second anyway. This works out the same as a higher shutter speed and gets rid of the camera movement.

If you're shooting in brigher light with the flash as fill in, then you need to worry about the shutter again.

Also, you don't need to factor in the crop sensor for focal length/shutter speed purposes. :)
Click to expand...

Thanks for all the info.
so what do i do if it is for fill flash?
what ISO should i use for indoor with flash photography?
 
You could also set 1/200 (or 1/250 depending on highest sync speed) and f4 in manual mode. The ETTL will work out the exposure for the flash. Or continue using 'p'.
 
I use a flash for work (new flash gun is arriving tomorrow...yay!).

When using the flash I always shoot in P mode (partly becuase I need to take a photo quickly and I don't have time to fanny around with settings) with an ISO of 100.
 
torque22 said:
taking pictures inside at night

how do i get decent pics at the correct shutter speed.
Click to expand...

I only ever use the flash with the camera set to M manual. The flash will calculate how much light to put out for your settings so you can just let it do its stuff.

Try setting 100 iso, F8 and 1/200th and take some shots in a normal room at night. You can set flash compensation if you want more or less light from the flash than it meters for. In a big room open up the aperture and/or raise the ISO if the flash does not have enough power. Remember anything that reflects the flash back at the lens will quench the flash and can cause under exposure.

Fill flash where you blend with available light is something completely different.
 
you're overestimating the correct shutter speed. The crop factor simply crops - for a rule of thumb like the 1/focal length one, you don't need to take into account crop factor. Think of it like taking a photo with a FF camera and cropping it. Now you've cropped it you don't suddenly need to use a higher shutter speed.
 
Not convinced you're right their Leo

Yes, as a crop factor it doesn't actually change the focal length of the lens, it just appears to do so by cropping into the image the lens could take if all of it was used

But any such crop is magnifying the image, and hence would magnify any problem with it such as camera shake - so the 1/focal length as a min shutter speed based on the crop magnification is still a safer option methinks
 
Thanks for all the advice and info everyone, I haven't had chance today to try anything yet but will have at the weekend. (famous last words)
 
DiddyDave said:
Not convinced you're right their Leo

Yes, as a crop factor it doesn't actually change the focal length of the lens, it just appears to do so by cropping into the image the lens could take if all of it was used

But any such crop is magnifying the image, and hence would magnify any problem with it such as camera shake - so the 1/focal length as a min shutter speed based on the crop magnification is still a safer option methinks
Click to expand...


In the end, it's a rule of thumb rather than something to follow religiously. However, I have got plenty of sharp photos at 1/300 with a 300mm lens, and I have also got a relatively sharp photo at 1/15th with a 15mm lens on a P&S (crop 7times) with no IS...

It's going down the wrong path to use "magnifies" with anything regarding crop. While an image may appear less sharp, it would be because, if you viewed it 100%, each pixel would be smaller, and so any shake would cover more pixels, than a 5D or whatever.

However, you could apply that "crop factor magnifies shake" concept to the 1Ds Mk III. At 22MP, it has the pixel pitch of a 13MP camera with a 1.6 crop sensor. Therefore, if you viewed a 13MP 1.6 image and a 22MP 1Ds image at 100%, they would show the same amount of image.
but to be safe, I'd just try and keep the shutter speed as high as possible anyway.
 
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