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 03/07/2011 08:44:18 AM · #1
A question came my way today. The person was shooting for the Day Taken at Night Challenge. In the very low light conditions, autofocus failed. Here is my response, in case others encounter same.

"Yes, in darkness, the autofocus system will fail you. The camera won't be able to find horizontal or vertical lines. The solution is to use Manual Focus. The data you are missing is the accurate prediction of the depth of field plane. For a given aperture size, you can be certain of the depth of field (a âzoneâ of acceptable sharpness) for a particular lens when focus is set to a specific distance. In the field, I use DOFmaster on my iPhone. There's also a website. And, the online calculator.

But, if you don't have access to DOFmaster, you can use the Zone Metering gauge on your lens. Well, at least most lenses have these marks. [ Just checked a picture of Canon EF-S 18-55mm f/3.5-5.6 II and it DOES NOT have that handy gauge.] So, you'll need to rely on DOFmaster, in one of its forms.

All I can say is.... you can trust your equipment to put things in the DOF plane in sharp focus if you set your manual settings as indicated in the DOFmaster guide."

I was surprised to discover the absence of the Zone Focus gauge on the EF-S lens. Canon took away a useful tool from a kit lens.

eta: lens picture

Message edited by author 2011-03-07 08:53:00.
 03/07/2011 09:02:55 AM · #2
Originally posted by hahn23:
A question came my way today. The person was shooting for the Day Taken at Night Challenge. In the very low light conditions, autofocus failed. Here is my response, in case others encounter same.

"Yes, in darkness, the autofocus system will fail you. The camera won't be able to find horizontal or vertical lines. The solution is to use Manual Focus. The data you are missing is the accurate prediction of the depth of field plane. For a given aperture size, you can be certain of the depth of field (a âzoneâ of acceptable sharpness) for a particular lens when focus is set to a specific distance. In the field, I use DOFmaster on my iPhone. There's also a website. And, the online calculator.

But, if you don't have access to DOFmaster, you can use the Zone Metering gauge on your lens. Well, at least most lenses have these marks. [ Just checked a picture of Canon EF-S 18-55mm f/3.5-5.6 II and it DOES NOT have that handy gauge.] So, you'll need to rely on DOFmaster, in one of its forms.

All I can say is.... you can trust your equipment to put things in the DOF plane in sharp focus if you set your manual settings as indicated in the DOFmaster guide."

I was surprised to discover the absence of the Zone Focus gauge on the EF-S lens. Canon took away a useful tool from a kit lens.

eta: lens picture

I had the same problem. My solution was to take a shot of the same scene in twilight while there was enough light for AF yo work, mark it and then use the mark in MF after dark.

03/07/2011 09:22:50 AM · #3
My solution was to bring out a flashlight. I lit the area I was going to focus on so that autofocus had enough light to work.

Another good option for anyone that has a hot shoe flash would be to use that to focus, and turn it off for the shot. Seems the red beams my 480 EX ii puts out help to quickly focus on just about anything (within reasonable distance of course)
 03/07/2011 10:30:25 AM · #4
Good suggestions for work arounds!

I had one other thought about this situation. When one has plenty of light for landscape images, it's pretty easy to stop down the aperture to f/18 or f/22 to ensure enough DOF to cover the subject at just about any focus distance beyond your arm's reach. But, in twilight/moonlight/starlight/streetlight there is not an abundance of light to make a pinhole-sized aperture effective. So, my plan (if it ever stops snowing) is to use a wide open aperture and ISO 400 (or ISO 800) to gather as much light as quickly as possible with shadows exposed correctly (a minimization of electronic noise strategy). To make that f/4 work, I'll need to focus at the hyperfocal distance and be aware of the minimum and maximum boundaries of the DOF plane.

So, what I'm doing is previsualizing my shot, which I will take on Wednesday night after sunset. Better to think this out in the peacefulness of day, rather in the chaos of night.
 03/07/2011 10:38:42 AM · #5
Originally posted by hahn23:
So, what I'm doing is previsualizing my shot, which I will take on Wednesday night after sunset. Better to think this out in the peacefulness of day, rather in the chaos of night.


Great advice. I went a small step beyond that and took some photos of the scene during the day. That allowed me to play with perspective, composition, etc with fast shutter speeds. Then when night came, I just had to go to approximately the exact same spot and only worry about how to expose the scene. That helped tremendously.
 03/07/2011 10:46:35 AM · #6
Originally posted by giantmike:
Originally posted by hahn23:
So, what I'm doing is previsualizing my shot, which I will take on Wednesday night after sunset. Better to think this out in the peacefulness of day, rather in the chaos of night.


Great advice. I went a small step beyond that and took some photos of the scene during the day. That allowed me to play with perspective, composition, etc with fast shutter speeds. Then when night came, I just had to go to approximately the exact same spot and only worry about how to expose the scene. That helped tremendously.

Super great advice! Thanks for sharing this.
 03/07/2011 12:08:11 PM · #7
Originally posted by giantmike:
Originally posted by hahn23:
So, what I'm doing is previsualizing my shot, which I will take on Wednesday night after sunset. Better to think this out in the peacefulness of day, rather in the chaos of night.


Great advice. I went a small step beyond that and took some photos of the scene during the day. That allowed me to play with perspective, composition, etc with fast shutter speeds. Then when night came, I just had to go to approximately the exact same spot and only worry about how to expose the scene. That helped tremendously.


I think this is a great solution, the place I plan on doing a long exposure is not too far away I could go there in the middle of the day get the correct focal length and play around with different scenes. Then when I go out at dark all the hard stuff will be taken care of.

Now if it will just stop raining.
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