Focusing in Low Light

[Divemaster]

Hey everyone, I was taking a few photos last night and was having a really hard time focusing on a sailboat in the dark (then I realized the faint waves were actually slightly rocking the boat, blurring the boat slightly - newbie, I know). We had a beautiful night last night and couldn't help but take a few pictures, but was wondering if anyone had tips on focusing in the dark? I was thinking that a flashlight, shinning on the boat would have probably been my best bet, but figured I would ask the pros.

Thanks for your help!


Matt

 

[tirediron]

A flashlight might have worked well if it was strong enough, but the easiest way for something that it is beyond the "infinity distance" of your camera is simply to set the lens to MF and focus on infinity.

 

[TheKenTurner]

A flashlight might have worked well if it was strong enough, but the easiest way for something that it is beyond the "infinity distance" of your camera is simply to set the lens to MF and focus on infinity.

But he wanted to focus on the boat. Not the infinity distance.....

A flashlight would probably work best unless you for some reason have a super strong flash.

 

[Robin Usagani]

always find the part of the subject with the most contrast. This boat is probably the roof where it has white reflection of the moon.

 

[tirediron]

A flashlight might have worked well if it was strong enough, but the easiest way for something that it is beyond the "infinity distance" of your camera is simply to set the lens to MF and focus on infinity.

But he wanted to focus on the boat. Not the infinity distance.....

A flashlight would probably work best unless you for some reason have a super strong flash.

Judging by the photo he posted, unless the OP is using a super-tele, than the sail boat is going to be well beyond the "infinity distance" of his lens, so setting it to MF and infinity will render the sailboat perfectly focused. There is no way that a flash is going to illuminate that scene.

 

[SoCalTiger]

A flashlight might have worked well if it was strong enough, but the easiest way for something that it is beyond the "infinity distance" of your camera is simply to set the lens to MF and focus on infinity.

But he wanted to focus on the boat. Not the infinity distance.....

A flashlight would probably work best unless you for some reason have a super strong flash.

Judging by the photo he posted, unless the OP is using a super-tele, than the sail boat is going to be well beyond the "infinity distance" of his lens, so setting it to MF and infinity will render the sailboat perfectly focused. There is no way that a flash is going to illuminate that scene.

EXIF data shows his focal length was only 26mm. Also, he was using F/10. At that focal length and aperture he definitely doesn't need to be at infinity. The boat was closer than you are thinking.

 

[KmH]

Auto focus needs light to work, because it detects the contrast that edges have.

A flashlight might, or might not have worked.

Another consideration with a short focal length is that using a small lens aperture is not as critical for having a good DoF.

DoF is controlled by more than just the lens aperture. Focal length and focus point distance also have A LOT to do with DoF.

 

[cgipson1]

A flashlight might have worked well if it was strong enough, but the easiest way for something that it is beyond the "infinity distance" of your camera is simply to set the lens to MF and focus on infinity.

But he wanted to focus on the boat. Not the infinity distance.....

A flashlight would probably work best unless you for some reason have a super strong flash.

A powerful spotlight might have worked if the boat was a ways off.. but if the boat has people on it, how do you think they would feel about that? And if it was wide enough cover the entire boat, it would also have spill to the sides... which would create a totally unnatural looking photo.

Anyway.. his focus was probably sharp... it was the 30 second exposure and the movement of the boat that caused the boat to be "fuzzy", everything else is sharp! If you look at the light on camera right that are reflecting in the water... they appear to be "sharp" for the entire photo.. you can actually see individual wavelets in the light all through the photo, with no appreciable change in "sharpness"! SO.. the OP had good focus, or at least adequate DOF to cover the boat too (especially with such a short focal length). But a long exposure and ANY movement.. and boom.. fuzzy!

Another clue is the top of the mast is "fuzzier" than the rest of the boat.. it would move more than the hull would, based on any rolling motion of the hull (the hull acting as the pivot)

 

[Divemaster]

Thanks for the information, I thought that the picture came out pretty good, I just never realized how much the boat was actually moving.

 

[KmH]

Use the spotlight/flashlight just to auto focus, lock focus (or switch to manual so it can't re-focus), turn out the spotlight/flashlight, and release the shutter.

 

[aussiearef]

I reckon if you focus on Hyper Focal Distance everything including the boat will be in focus: Hyperfocal distance - Wikipedia, the free encyclopedia