# Canon will not work in very low light



## Grandpa Ron (Apr 18, 2019)

I have a Canon Rebel T6 that I have been using for low light photography.

I have jacked the ISO up to 6400 for some nice star photos, I have tried various ISO values to capture landscapes with just the ambient sky glow. I have shots of the moon at it various phases.  All that seems to work fine.

However, occasionally the camera seams to sense there is not enough light for a photo and will not take a picture. I noticed this with the crescent moon. When I tried to reduce the exposure.

Is this normal, or should I be able to take a picture even with the lens cap on? 

I shoot most of these low light shots in Manual mode but I am wondering if I am missing something in one of the 472 camera settings in the menu.


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## Banjor (Apr 18, 2019)

Grandpa Ron said:


> However, occasionally the camera seams to sense there is not enough light for a photo and will not take a picture. I noticed this with the crescent moon. When I tried to reduce the exposure.
> 
> Is this normal, or should I be able to take a picture even with the lens cap on?



If you have one-shot focusing enabled, and you are using AF, the shutter won’t fire if the camera can’t find focus. Switching to MF will let you take pictures even if they are out of focus.

If you are shooting the moon, just switch to MF and focus on infinity.


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## Derrel (Apr 18, 2019)

"one-shot focusing" enabled= AI Servo, in Canon-speak, no?


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## zombiesniper (Apr 18, 2019)

Derrel said:


> "one-shot focusing" enabled= AI Servo, in Canon-speak, no?



Canon calls one shot focussing  "ONE SHOT", AI SERVO is continuous auto focus and AI FOCUS is a bastardized combo of the two.


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## Derrel (Apr 18, 2019)

I never use single focus, unless I NEED a speedlight and its AF assist beam. I prefer AF-C 99.5% of the time, and have NO USE,at all, for AF-I, a really  stupid idea IMHO


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## photoflyer (Apr 19, 2019)

Turn the AF off and then try focusing manually through live view.


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## Grandpa Ron (Apr 19, 2019)

Nothing beat the collective wisdom of the photo group.

I switched to manual focus and all is good.

Thank you very much.


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## Dao (Apr 19, 2019)

Some hot shoe flash has a Auto focus assist beam/LED that can also help.


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## Derrel (Apr 19, 2019)

Dao said:


> Some hot shoe flash has a Auto focus assist beam/LED that can also help.



AF assist usually requires 1) AF enabled in 2) single shot AF mode..no Continuous or AI Servo mode focusing.


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## Dao (Apr 19, 2019)

Derrel said:


> Dao said:
> 
> 
> > Some hot shoe flash has a Auto focus assist beam/LED that can also help.
> ...



Yup, that is right!


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## Derrel (Apr 19, 2019)

One night in the mid-1990's we had some raccoons in our back yard and I tried to get a few pics using a MF film camera and a flash.Had I owned an AF camera and flash, it would have been trivial to capture some well-focused shots.


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## TCampbell (Apr 20, 2019)

"One Shot" uses a behavior called "focus priority"
"AI Servo" uses a behavior called "release priority"

Focus priority says that when you press the shutter button, the camera's priority is to assure focus has been achieved before taking the shot.  This means the AF point you selected (or at least one AF point if you allowed the camera to auto-select from any AF point) must have confirmed focus or it wont take the shot.  If there isn't adequate light to allow a focus lock, then it will give up and you get no shot at all.  This only happens if the lens is set in auto-focus (AF) mode.  It will take a shot if you switch to manual focus.

Release priority says that when you press the shutter button (completely), it _will_ take the shot immediately -- whether it had time to focus or not.  Use with care ... half-press and make sure you are happy that it has achieved focus before you completely press the shutter.  If you press it completely without pausing to wait for focus, you'll just get a bunch of out-of-focus shots.  But this is usually used by people doing action photography who are tracking their subject while holding the shutter button in the half-pressed position (and the camera will continue to focus) ... that way when you find that decisive moment when you want the shot, you can press the shutter completely and it WILL take the shot immediately.


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## BasilFawlty (Jun 1, 2019)

photoflyer said:


> Turn the AF off and then try focusing manually through live view.


Agreed.  And just to add to that, when shooting the moon, I'd suggest using a tripod and, while in live view, use the Zoom Function to zoom in to x10 zoom and then use manual focus to get the sharpest edge of the moon that you can (which may not necessarily be at full infinity)


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## Grandpa Ron (Jun 1, 2019)

I thought it strange that the sharpest focus in not at Infinity.

But I did not make the optics. I just use them the way they work.  

Thanks for the tip, I thought it might be something wrong in the optics.


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## BasilFawlty (Jun 1, 2019)

Grandpa Ron said:


> I thought it strange that the sharpest focus in not at Infinity.
> 
> But I did not make the optics. I just use them the way they work.
> 
> Thanks for the tip, I thought it might be something wrong in the optics.



It's reasonable to think that full-stop infinity would be where you would put it for focus on very far objects.  Seems logical.  But, for example, on my Rokinon 14mm, when I'm focusing on stars, the sharpest focus I get on stars is  just a little but off of full-stop infinity.  If I go beyond that, the stars start to get unfocuses.  Weird, I know.


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## Derrel (Jun 1, 2019)

Some lenses focus "beyond infinity". Yes, that's possible.


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