50d dosen't want to take a picture

OK, I'm trying to keep on learning photography. Today I decided to take some photos into completely darked room. I try to do that in TV priority and I set up 30secs shutter speed. But my Canon 50d doesn't want to take a picture. I use 50mm 1:1.4 lens. When I turn on the light it works perfectly. What is wrong?

OK, I got the answer. I was in "Auto Focus" mode. I switched to manual and it takes photos under every circumstances.

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Originally Posted by Banner1976

OK, I'm trying to keep on learning photography. Today I decided to take some photos into completely darked room. I try to do that in TV priority and I set up 30secs shutter speed. But my Canon 50d doesn't want to take a picture. I use 50mm 1:1.4 lens. When I turn on the light it works perfectly. What is wrong?

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It's too dark and the camera can't lock focus on anything, it will not fire while in AF lens mode. You will need to switch lens to manual, and manually focus then release the shutter.

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Originally Posted by Amberglass

It's too dark and the camera can't lock focus on anything, it will not fire while in AF lens mode. You will need to switch lens to manual, and manually focus then release the shutter.

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I switched lens to manual, and it works so far. Thank you!!

In certain situations where there is not enough light but not completely dark, the lens might "hunt" (will keep focusing and re-focusing) to try an lock on to a point. In this case, it's best again to switch to manual on your lens. But in really difficult lighting situations, you're better off going completely manuel mode and dial in your f stop and shutter speed; gauge your exposure with the camera's meter.

It's not unusual to go completely manual on lens and camera either;). Just remember that in P, Av, and Tv mode, the camera will be doing most of the guess work for you. Again, there will come times where you "have to take the wheel" because the camera says you can't, when in truth you can but only when on manual:).

Hi Banner,

If you're experimenting with low-light photography (on a tripod) the easiest thing to "sort out the focus" is to simply have the room lights on (or use a torch) - let the camera focus - switch the lens to MF (focus stays in the same place) - lights or torch off - and then take the shot.

You could open the aperture as wide as possible and bump up the iso as high as possible; autofocus then switch to manual before returning iso and settings to what they were. But if it is really dark let the flash assist the focus. :)

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Originally Posted by Amberglass

In certain situations where there is not enough light but not completely dark, the lens might "hunt" (will keep focusing and re-focusing) to try an lock on to a point. In this case, it's best again to switch to manual on your lens. But in really difficult lighting situations, you're better off going completely manuel mode and dial in your f stop and shutter speed; gauge your exposure with the camera's meter.

It's not unusual to go completely manual on lens and camera either;). Just remember that in P, Av, and Tv mode, the camera will be doing most of the guess work for you. Again, there will come times where you "have to take the wheel" because the camera says you can't, when in truth you can but only when on manual:).

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I think it's gonna take several weeks before I will be able to go completely manual. However, it's my goal.

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Originally Posted by Colin Southern

let the camera focus - switch the lens to MF (focus stays in the same place) - lights or torch off - and then take the shot.

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Tonight I will apply this trick. Thank you.

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Originally Posted by Banner1976

I think it's gonna take several weeks before I will be able to go completely manual. However, it's my goal.

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If you don't have a copy, I highly recommend Bryan Peterson's photography series:

Understanding Exposure: How to Shoot Great Photographs with a Film or Digital Camera
Understanding Shutter Speed: Creative Action and Low-Light Photography Beyond 1/125 Second

or

Bryan Peterson's Understanding Photography Field Guide: How to Shoot Great Photographs with Any Camera

His books are written in a very easy to understand format with fun and easy assignments. My 10 year old daughter just started photography herself and has read these books, that's how easy it is to nail great exposures;). And she went straight to fully manual btw. Because of the instant gratification of the lcd on back (she's using a Nikon D70s), she can see where her mistakes are and/or where she needs to improve/adjust. Patience and tons of practice is the key not age:).

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Originally Posted by Amberglass

If you don't have a copy, I highly recommend Bryan Peterson's photography series:

Understanding Exposure: How to Shoot Great Photographs with a Film or Digital Camera
Understanding Shutter Speed: Creative Action and Low-Light Photography Beyond 1/125 Second

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I just ordered both of them! Plus: Understanding Close-up Photography: Creative Close Encounters with or without a Macro Lens.:D

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Originally Posted by arith

You could open the aperture as wide as possible and bump up the iso as high as possible; autofocus then switch to manual before returning iso and settings to what they were. But if it is really dark let the flash assist the focus. :)

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I did the opposite for a low-light photo. I dropped the ISO down to 64, used an 15 second shutter speed with auto focus, and incandescent white balance. My histogram showed low values yet my highlight indicator picked up some over exposed pin points of light. The room was totally dark but I had a small shaft of light flowing into the room from another area.

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Originally Posted by Banner1976

I just ordered both of them! Plus: Understanding Close-up Photography: Creative Close Encounters with or without a Macro Lens.:D

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Examples of macro work without the use of a macro lens, both taken with 50 1.4:

http://backup.cambridgeincolour.com/...95dd4c70_b.jpg

http://backup.cambridgeincolour.com/...c7c3192a0f.jpg

Just encouraging you Banner1976:).

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Originally Posted by arith

You could open the aperture as wide as possible and bump up the iso as high as possible; autofocus then switch to manual before returning iso and settings to what they were. But if it is really dark let the flash assist the focus. :)

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Hi Arith,

I'm afraid that this "trick" is for metering, not focusing - it doesn't make an ounce of difference to the AF as the aperture is always wide open while focusing, and the ISO is a hardware amplification to the signal being read off the sensor after the shot is taken.

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Hi Arith,

I'm afraid that this "trick" is for metering, not focusing - it doesn't make an ounce of difference to the AF as the aperture is always wide open while focusing, and the ISO is a hardware amplification to the signal being read off the sensor after the shot is taken.

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Cor; that is what I've been doing. Must be just lucky. :confused:

I'm virtually blind and in a dark place haven't got a hope of manually focusing, so I've been doing that and choosing a similar distance more lightly lit places as well as turning the camera on its side; but I thought it was working.

Otherwise I pop the flash up. Well, what do I do now in a really dark place out of range of the flash apart from guess:(

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Originally Posted by arith

Well, what do I do now in a really dark place out of range of the flash apart from guess:(

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Hi Arith,

There's quite a few techniques you can use ...

- Get to know your depth of field for the distance / aperture / focal length that you're shooting; If you're shooting at a relatively small aperture then focusing isn't critical.

- Use a torch to illuminate the subject - focus - then switch to manual focus (I have the same problem with early morning shoots, so I use a 6x D-cell torch with a 600 lumen 3x LED kit on the end - works a treat).

- Focus on something else at the same distance and then switch to manual

- Use the distance scale on the lens

There's ALWAYS a way :)

Cheers; I always use f8 in dark places like Cathedrals with their windows covered and 28mm lens so my hyperfocal distance is 5.2 metres. A 56mm lens is 4 times further so 50mm probably 20 metres.

The actual dof is more of a guess for closer distances but I was given a rule of thumb fomula which I've forgotten but was something like (size of definable object)/WD x 3.2 x (distance of object focussed on) where WD is (focal length)/(f-stop).

I did say it was rule of thumb.:)
So say that if we require an object 1mm in size to be definable on a 28mm at f8 where the object is 1 metre away we get 2/7 x 3.2 or 90 centimetres.

Don't seem right to me; but instead using the CoC of approximately 0.02mm gives 1.8 centimetres in my head.

Using thishttp://www.dofmaster.com/dofjs.html

gives 39 centimetres; so maybe I just forgot the rule or it just doesn't work. :)

I haven't really had a problem with focussing yet though and usually only use AF to get an idea of distance then using the scale on the camera for a rough idea of dof.

Is there an easy to remember rule of thumb? I've got one for hyperfocal distance but dof from these equations is hard to do in my head.http://www.dofmaster.com/equations.html

Actually forget what I said because I've just had another look and the equations just look like H/(H+s) and H/(H-s) of course both times distance. Where H is the hperfocal distance and s is focus distance.