Nidelva river through Trondheim Norway

Nidelva river through Trondheim Norway
by Saaru Lindestokke                

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So I've just started getting into photography. I'm currently experimenting with taking long exposure photos at night, but my house doesn't have the ideal surroundings for a good pic. Is there any way to make a SLR camera just take a picture of what it sees without focusing? (e.g just of the dark sky)

Right now, I have to point it at a light source and then quickly flip it upwards at the sky. Canon EOS Rebel by the way. I have a shutter release remote, though it still has to focus when you use it.

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8  
turn on Manual Focus – Ryan Feb 28 at 19:48
    
The phrase "just take a picture of what it sees without focusing" seems to imply that focusing is an extra, nonessential effect. That's not the case — "what it sees" is what's in focus (and/or blur, of course). Maybe that's not what you meant, but if it is, or for others with that same thought, see How can I take a photo with everything in focus with my DSLR? – mattdm Feb 29 at 1:13
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Possible duplicate of How do I focus in low light for long exposures? – Michael Clark Feb 29 at 4:21
up vote 9 down vote accepted

Your question boils down to auto vs manual focus. From the methodology you've described, it seems that you are attempting to use autofocus to get a picture of the night sky. That's not a great plan because the objects your camera can focus on in the night sky are pretty small points of light, and autofocus usually only works well under brightly lit conditions. You do have a couple of options though, both with and without auto focus.

Regardless of if you're going to attempt auto or manual focus, the fist thing you'll want to do is spin the dial to M mode. If you let the camera guess your exposure at night, you're unlikely to be happy with the results.

If you want to keep using auto focus you have a few option. The first thing you'll want to do is set your AF point selection to manual mode and select a single point. A quick google for your specific model should tell you how to do this, but you should end up somewhere in the menus that looks like the below image.

AF Point Selection Screen

You'll also want to set your AF mode to One Shot. This is likely set in a very similar way to the AF point selection above. This will keep the camera's focus locked once you set it. If you have it set to the other modes the camera will attempt to adjust the focus as you move your camera from one object to the next, which is precisely what we're trying to avoid.

AF Mode Selection Screen

Now aim your camera at a far away bright object, like a street lamp way at the end of your road. Line the object up under your focus point and press your shutter button half way and then hold it. Your focus should now be locked, and as long as you keep the shutter held halfway down it shouldn't move. You may now leisurely point your camera at the sky and fully depress the shutter release to take your picture. If you're using a tripod though, which you should since you're asking about long exposures, this may be a little difficult to pull off without taking a few accidental pictures on the way to repositioning the camera towards the sky.

Another option very similar to the last is to use the AE Lock button on the back of your camera to focus the distant object, instead of the half shutter press. See the below image for its location. You'll probably have to perform some setting in the menu of your camera to get this to work since by default this button locks exposure instead of focus, so again a quick google search for "rebel back button focus" will be your friend.

Back Button Focus

A final autofocus option is to use either of the above options to focus on your distant object and then switch your lens to manual focus. First thing you'll want to do is look at the left side of your lens (if it's attached to the camera, see image below). Here you should see at least one toggle switch with something like M on one side and A on the other. M stands for manual focus and A stands for autofocus. Right now it should be flipped towards A. This time, after you've focused on your distant object release your focusing button and the flip the switch in the side of your camera to M. Congratulations, you're now in manual focus mode and your focus point is locked unless you change it. You could use your remote to take a picture using this method or any of the methods I'll describe below.

Side View of Rebel and Lens

The problem with any of the above methods is that you're approximating your sky focus point (at infinitely) with something that is potentially much closer. This means there is a good chance that after you attempt any of these methods you may still end up with your sky photograph out of focus. This is why I would highly recommend manually focusing on the sky itself.

To do this, start out by flipping the toggle on your lens to M. Now that your lens is in M mode you have to set the focus point manually. Somewhere on the lens is a focus ring. I'm guessing it will be at the far end of your lens, right next to the glass like in the photo above, but it may also be in towards the camera body. If you're using a zoom lens it's going to be a ring that is considerably smaller than the one that zooms the lens. Point your camera at the sky and spin this ring to one of it's stopping points. If you spin it in the direction of infinity your stars should be pretty close to small points of focused light. If you spun towards the near focus end of the focus range they'll be large, diffuse balls of light. If that's the case spin to the other extreme of the focus range.

Now that you're focused at infinity, start spinning the focus ring in the only direction it can go. You'll need to play with the focus a little around this range until you get the sharpest stars you possibly can. If you have live view on your camera I would highly recommend using it here. While in live view use the live view 100% zoom to blow up your sensor's image and point your camera at a bright star. Then use the focus ring to make this star sharply in focus and you should be all set.

Now all you have to do is play with the exposure settings, or look up some starting points online, and you'll be taking focused, long exposure night photographs in no time.

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Your fourth paragraph only works if the camera is set to "One Shot" AF mode. In "AI Servo" the camera will continually try to refocus wherever it is pointed. In "AI Focus" the camera will hold focus for a few seconds, then shift to "AI Servo" if it can't confirm focus is being maintained. – Michael Clark Feb 29 at 4:26
    
Good callout @Michael. Edited the post to include an AF mode setting step. – tittaenälg Feb 29 at 4:45
    
One way to screw up manual focus is if the viewfinder focus adjustment is off. It's worth checking. A quick way to do this is autofocus on a high contrast object, then tweak the little dial on the viewfinder. Then manual focus and take a test image. – Chris H Feb 29 at 6:52
1  
The viewfinder can't be more in focus than the image projected on the viewscreen. Softness in the viewfinder due to a mis-adjustment of the diopter wheel will never cause it to be sharper than the image projected on the viewscreen, only less sharp. Adjusting the diopter control will have no effect on a focus issue caused by the viewscreen distance from the lens (via the mirror) being different than the image sensor distance from the lens. – Michael Clark Feb 29 at 8:04
    
Also, I'm pretty sure that if you simply aim for "best focus" in the viewfinder, then diopter adjustment doesn't matter. I'm also pretty sure that for photographing the night sky, if the lens does what it says on the barrel, just focusing on infinity will be good enough in the huge majority of cases. – Michael Kjörling Feb 29 at 8:47

If you are taking picture of stars, then the camera needs to focused at infinity, instead of at some near light source. Such dark sky picture surely uses a wide aperture with little depth of field, so this is doubly important. At least focus on a light source way down the street (far away).

Or better, in manual focus mode, just setting the lens to its infinity mark will help But this is NOT necessary turned as far as it will go, it will likely go beyond infinity. Stay on the mark.

Or better yet, if your camera offers live view focusing, and allows you to zoom in deeply into that live view screen presentation, then when zoomed greatly (meaning, zoomed into live view, NOT with the lens), then you should be able to see individual bright stars, and can focus manually on one.

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If you're just playing around with a kit lens, trusting the focus mark isn't likely to get very sharp results compared to manual focus. – Chris H Feb 29 at 6:50
    
plus live view can be set to be bright independent from the actual exposure, which makes the stars more visible and easier to focus on. – null Feb 29 at 14:25

A DSLR stops performing autofocus when in manual focus mode. Most times, there is a switch on the side of the body next to the lens mount to due just that. This varies by camera but universally manual focus is indicated by the MF acronym.

Many lenses also have a manual focus switch or a kind of clutch for some Zuiko and Tokina lenses. In any case, setting either the body or lens to manual focus will work. No need to do both.

Once you are in Manual Focus mode, the camera will not autofocus. The lens will simply focus at the distance it is set for at that time. Anything closer or further (unless you are focused on infinity) will be out-of-focus. To adjust what is in focus, you have to turn the focus ring on the lens.

If you are looking to make more or less things in focus, search for questions regarding Depth-Of-Field on this site.

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"Most times, there is a switch on the side of the body next to the lens mount to [switch to manual focus]." Where the switch is is camera-dependent. On Canon cameras, the auto/manual focus button is on the lens, not the camera. – David Richerby Feb 29 at 2:37

Other than manual focus way to accomplish what you want is to use back focus button. The idea behind is to separate the action of focusing from shutter button and to assign it to some other button (when is possible of course). I shoot all the time with back focus button and I am perfectly happy with this way

According to this Canon webpage BBF is applicable for EOS Rebel T3, T3i, T4

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The Rebel series (mentioned in the question) doesn't have a dedicated back focus button. Some of them allow the exposure lock button to be remapped to use as a back focus button, but I'm not sure all of them do. – Michael Clark Feb 29 at 4:13
    
@MichaelClark, according to this Canon webpage: learn.usa.canon.com/resources/articles/2011/… BBF is applicable for EOS Rebel T3, T3i, T4i – Romeo Ninov Feb 29 at 7:48
    
It is applicable if the exposure lock button is remapped to serve as an AF-ON button. Your answer ignores the need to remap a button set to another function by default. But that doesn't make much difference when there's not enough contrast in the night sky to allow AF to function at all, other than for the moon and brighter clouds. – Michael Clark Feb 29 at 9:02

Any process that requires that you press and hold a button while taking the shot, or even half-depress and hold the button, is destined to fail. The exposure time will be in the range of many seconds, perhaps as long as 30, and no-one can hold perfectly still for 30 seconds. Even if you hold your breath, your heart still beats.

The only method I recommend is to set the mode to M for manual, set the focus and use a remote release or self-timer so that you don't actually touch the camera as the photo is being taken.

To establish focus, there are a few options. First, some, but not all, lenses actually focus at infinity when set to infinity. You can test by setting the camera to M for manual, turn off AF on the lens, set the focus to infinity and then I suggest an aperture as wide as the lens will get, f/3.5 or f/2.8 or even wider, an ISO of 3200 and an exposure time of 20 seconds. Take the shot. Are the stars in sharp focus on the preview screen when zoomed in? If so, you are all set. Adjust the exposure time and ISO until you have an acceptable image.

If your lens does not actually focus at infinity when set to infinity, then we still have options. First, I suggest you set the focus manually by using, not the street-light at the end of the street, but the furthest light you can find. At one of my favorite night sky shooting locations, there is a barely visible light on the front of a house that is 3/4 mile away. When I focus using that light and then recompose on the stars, I get perfect focus.

The next method uses a green laser pointer. I bought one recently for under $13 US. Laser pointers can be very dangerous. Never point yours at any person or living animal and especially not at an airplane. You will probably go to jail for pointing a laser pointer at an airplane.

My technique is to point to the top of a tree that's 100 feet or more away. The spot is clearly visible and I can focus pretty easily. Recompose on the stars and shoot.

Finally, there is trial and error. Manually focus the lens at your best guess at infinity focus. Take a shot. Zoom in on a star on the LCD. Is it in sharp focus? If not, make a slight adjustment and try again. Keep going until you get a good one and enjoy.

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I did once photograph the night sky during new moon using a Canon 7D and the Tokina 11-16mm f/2.8 lens. In these conditions, it was way too dark for the camera's autofocus to be able to focus on anything.

Fortunately, even at f/2.8, switching the lens to manual focus, and setting focus to infinity, i.e. turning the focus ring until it would not turn anymore, did manage to bring the night sky in focus, as well as everything more than a few meters away. This will not work for all lenses however, as with many lenses, when the focus ring is turned all the way, their focus point is actually beyond infinity.

So the main problem in my case was not that of focus - it was actually composing the image as it was near impossible to see anything in the view finder.

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Be aware of that when most modern lenses focus past infinity when turned all the way to the stop. – mattdm Feb 29 at 15:40
    
@mattdm - I did intend to imply that in my answer, but I can see I wasn't very successful in that respect. I updated the answer to better reflect that – Pete Mar 1 at 8:10

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