focus in bad light: possibly a silly question

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soliberus

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I'm the relatively new owner of a D40 and I'm struggling with taking photos indoors (bad light).

How do I focus/expose in bad light when I use the flash (onboard), as the flash only fires once the shutter opens... there is no pre-flash to assist with focus/exposure before the actual photo is taken?

I hope my question makes sense :|
 
Manual focus, get a faster lens, or increase the amount of light.

I have used a torch before, works in a pinch...
 
:lol: use a torch...i haven't thought of that one :lol:

Yes, the kit lens isn't exactly known for it's sheer speed. I guess manual focus is the answer in my case... or perhaps a torch ;)
 
Turn the focus assist light on. Pretty sure it'll tell you how to do that in the manual.
 
Are you aiming the focus point at something with good contrast? e.g. aim at an eye, or mouth, or logo, not a smooth cheek or a plain, featureless area of clothing. Perhaps aim at something else, the same distance away, but with better light or contrast. Then recompose back to your subject.
 
or measure the distance and set the focus manually using the dial on the lens - you know - the way they did it in the old days ;)
 
another alternative is if you've got a flash (eg nikon sb600/800/900, don't know what offbrand flashes do it), then it has a fantastic grid illuminator built in, that basically shines a red grid of lines at the subject, that helps the camera focus.
 
soliberus said:
I'm the relatively new owner of a D40 and I'm struggling with taking photos indoors (bad light).

How do I focus/expose in bad light when I use the flash (onboard), as the flash only fires once the shutter opens... there is no pre-flash to assist with focus/exposure before the actual photo is taken?

I hope my question makes sense :|
Click to expand...

Hi I have just tried my D40 and kit lens in a dark room.
It focused OK without the assist light - 2 sec at f4.2.

Of the three focusing areas only the middle one is sensitive to both horizontal and vertical detail. The outer two are sensitive to horizontal detail only (with the camera in landscape orientation)

Why do you think it is not focusing?
Are the pictures out of focus?
or is it that you are not getting a focus point light up ?
or is it that you are not getting a beep?
 
That shows the lens has indocators for the focal length Steve - not the focus distance
 
I have a hazy recollection that only the central focussing point works with AF-Assist in low-light...
Check what the manual says about that - pretty sure it did for the old D100 - I'd imagine that the older tech is still in use on lower-spec cameras as well...
 
Arkady said:
I have a hazy recollection that only the central focussing point works with AF-Assist in low-light...
Check what the manual says about that - pretty sure it did for the old D100 - I'd imagine that the older tech is still in use on lower-spec cameras as well...
Click to expand...

I don't use AF Assist as my D40 seems to focus OK without it, as long as I orientate the focusing points correctly but I have just tried it and you are right, the light only comes on when the central focusing point is selected.
 
itsdavedotnet said:
another alternative is if you've got a flash (eg nikon sb600/800/900, don't know what offbrand flashes do it), then it has a fantastic grid illuminator built in, that basically shines a red grid of lines at the subject, that helps the camera focus.
Click to expand...

:plusone:

I do this from time to time, the grid lines lights are more powerful than the on camera assist, also less distracting.
 
AndyB said:
or measure the distance and set the focus manually using the dial on the lens - you know - the way they did it in the old days ;)
Click to expand...

I use the split prism and line up the edges :D

itsdavedotnet said:
another alternative is if you've got a flash (eg nikon sb600/800/900, don't know what offbrand flashes do it), then it has a fantastic grid illuminator built in, that basically shines a red grid of lines at the subject, that helps the camera focus.
Click to expand...

also it lets you focus on something without contrast like say a plain white wall as the grid is what it focuses on :D
 
@suvv

Sometimes I don't get a beep. The focus assist comes on and you can hear the auto-focus motor trying to focus, but it's just not focusing. Other times it does focus, but then afterwards the photos is soft/slightly out of focus.

It's a bit of a hit-n-miss for me.

I'm going to turn this question into metering direction...

When the camera takes a meter reading (in bad light), does it take into account the flash will fire and adjust the exposure accordingly...or does it expose as if the flash is not going to fire?
 
my camera has differing settings for flash
auto
red eye
slow

auto sets the speed..depending on the zoom setting anywhere from 1/30 to 1/80...
red eye i dont use
slow allows me to set the speed and also get some ambient lighting on the shot to come through

speed isnt really what flash is about ...its power and distance along with fno

i adjust my flash power to compensate for burning out if i am using slow setting

my flash power can be adjusted +/- 2.0...it remains i have to experiment quite a bit to get a good balance between ambient and the fill

letting the flash supply all the illumination is a last resort..but usually the only one leaving the shots looking like cut out images
 
soliberus said:
@suvv

Sometimes I don't get a beep. The focus assist comes on and you can hear the auto-focus motor trying to focus, but it's just not focusing. Other times it does focus, but then afterwards the photos is soft/slightly out of focus.

It's a bit of a hit-n-miss for me.

I'm going to turn this question into metering direction...

When the camera takes a meter reading (in bad light), does it take into account the flash will fire and adjust the exposure accordingly...or does it expose as if the flash is not going to fire?
Click to expand...

Regarding focusing it may be that the camera is using one of the outer focusing areas as it is set to Closest subject. The outer focusing areas are sensitive to horizontal detail only and may have trouble focusing.

Set the AF-area mode to Single area, the bottom option. You then use the L & R on the 4 way switch to choose which of the 3 focusing areas you want to use. If you look through the viewfinder while changing the areas you will see them flash red as you select them, make sure that the centre one is selected. Take a shot using the centre focusing area and see how it goes. If you are shooting something without much horizontal or vertical detail try rotating the camera slightly to see if it focuses, if it does keep the shutter button pressed and move the camera back to where you want it.

Regarding the flash the camera does take into account that the flash will fire, in fact there is a pre-flash before the shutter opens to determine how much flash is needed.
It is quite complex but in matrix and centre-weighted metering the camera tries to balance the flash and the ambient light and to prevent overexposure of the subject by the flash.
In spot metering the flash and ambient exposures are determined independently and the camera tries to get the flash exposure of the subject correct regardless of the ambient brightness.
 
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