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Railfan Technology > A shot in the dark (how to focus in the dark?)


Date: 09/23/07 03:48
A shot in the dark (how to focus in the dark?)
Author: Mgoldman

I've never had problems with my Minolta XD-11, nor my Canon A2E when it came to
focusing a scene in the dark.

The Minolta, well it was manual, my eyesight was better and there was a split
screen for focusing.

The Canon had nine focus points and all I had to do was light the subject up
and line one of the red boxes up until I got confirmation from the camera by
way of a beep indicating it was in focus.

Last night, I was taking pictures of a still subject with my new 40D, I had
a tripod, I had a shutter release cord, and I had a large flashlight to
illuminate the subject in order to get a focal lock. I got it. I turned the
camera to manual focus to avoid hunting and took a 30 second exposure at f8
ISO 200 - and... it was blurry! I refocused every time, most were blurry.
The subject was my car and the focus point was the front wheel from about 18'
or so at 28 mm. All in high res 8 MP+ and unsharpmasked in PS. Canon L zoom,
24-105.

Attached see the best (my final manually focused car) and the worse of
my attempts (the soft F3's - seem relatively sharp, but they do not
"pop" note the wording and head light).

It wasn't until I used my best squint and guess that I was able to manually
focus it and I was good from that point forward. Very difficult without a
split screen focus screen and only a $20.00 pistol light.

How is it done? Doesn't a beep and a lit focus square verify focus?
If not, without a split focus screen, how do you know when you are
focused if you have very low light? Most len's seem to focus past infinity
also confusing the matter - focus all the way to infinity and then back a
hair seems rather iffy.

Suffering from a spat of photography amnesia... Thanks for your thoughts.







Date: 09/23/07 03:54
Re: A shot in the dark (how to focus in the dark?)
Author: Mgoldman

Here's what wheely bothered me in my initial attempts to
capture the car, despite lining up the focus point on
this very spot (cross haired focus point, at that) and
getting confirmation by the camera by way of a beep.




Date: 09/23/07 04:01
Re: A shot in the dark (how to focus in the dark?)
Author: Mgoldman

I am asking myself, why is it so hard to focus on an inanimate object?
Or, what am I doing wrong, these days.




Date: 09/23/07 04:16
Re: A shot in the dark (how to focus in the dark?)
Author: Mgoldman

I know I'm zooming in a bit, but it is noticable in
the uncropped image. What is shown is the point at
which the camera was focused on (acutally the number
boards just near the headlight and logo). This was
taken with autofocus using a 20D.




Date: 09/23/07 04:58
Re: A shot in the dark (how to focus in the dark?)
Author: Amtrak288

I love night photography! Focusing at night is no easy task, I found out with my Canon EOS Rebel T2 (It's a film camera, yes some of us still shoot film!) and I learned that once you have a fixed point in focus that you should turn off the Auto Focus so it doesn't continue to hunt around. I would think that once you have attained your focus point, then the image should remain in focus, however, I have learned in my travels that you shouldn't open the lens up wide-open (largest aperature) because of a loss of depth of field, which may contribute to the loss of focus, though this also depends on the lens your using. I usually shoot my night photos at f5.6. Here is a recent shot of Amtrak's Lake Shore Limited that I took a few weeks back. The photo specs are listed below:

Film: Kodak Ektachrome E100VS Pro 35mm Slide
Camera: Canon EOS Rebel T2
Lens: Tamron 28-80 f3.5-5.6 Zoom Lens
Exposure: f5.6 at approximately 30-35 seconds
Scanner: Epson Perfection 4490 Photo
Image/Color Correction: Adobe Photoshop CS3
Note: The lights on the platform at this station are the high-pressure sodium type that yield very "yellow" light so it took a bit of work in Photoshop to filter out that light!





Date: 09/23/07 06:32
Re: A shot in the dark (how to focus in the dark?)
Author: pennsy3750

Mitch -

You might try putting a small flashlight (ie, point light source) on your subject or on the ground near it. This gives you a reference point to manually focus.



Date: 09/23/07 11:18
Re: A shot in the dark (how to focus in the dark?)
Author: nls

Mitch, is that an IS lens you're using? If so, when taking shots off of a tripod, especially such long exposures, you really have to turn the IS off, as it will continue an attempt to stabilize, which makes the shots blurry. I can't see the big versions of your shots to tell if that really is the problem, but I've learned this the hard way!

Nick S.

http://www.nicksuydam.com



Date: 09/23/07 11:50
Re: A shot in the dark (how to focus in the dark?)
Author: Mgoldman

nls Wrote:
-------------------------------------------------------
> Mitch, is that an IS lens you're using? If so,
> when taking shots off of a tripod, especially such
> long exposures, you really have to turn the IS
> off, as it will continue an attempt to stabilize,
> which makes the shots blurry. I can't see the big
> versions of your shots to tell if that really is
> the problem, but I've learned this the hard way!
>
> Nick S.
>
>
AS mentioned originally, I am using a point source
light (pistol grip high powered flashlight) and an
appeture that is not wide open (f8 give or take).

As for IS, that very well could be it! I thought
about that just last night prior to my last few
shots and said - hmm.... Thanks for the confirmation.
Things did improve after I turned it off but at the
time I also was on manual focus. It could be that
simple, as I have just started to use the IS lens.



Date: 09/23/07 13:04
Re: A shot in the dark (how to focus in the dark?)
Author: engine3420

Back in the late 60's when I worked as a television camerman at a local station(KCOP-TV) whether I had the wide shot camera or the close-up ...I would zoom in tight on the subject and get my focus(manually) and then pull back out, you always got the best focus this way and it works the same for a still camera as long as your using a zoom lens and this is what I use because my 63 year old eyes (wearing glasses) cannot see well enough to use a fixed lens.

Chris





Date: 09/23/07 19:29
Re: A shot in the dark (how to focus in the dark?)
Author: lynnpowell

Mitch, you need to worry about that missing lug-nut on the front wheel of your car, too!



Date: 09/23/07 20:19
Re: A shot in the dark (how to focus in the dark?)
Author: Mgoldman

lynnpowell Wrote:
-------------------------------------------------------
> Mitch, you need to worry about that missing
> lug-nut on the front wheel of your car, too!

D'oh! I think it's just a plastic cap, but
thanks.



Date: 09/24/07 19:31
Re: A shot in the dark (how to focus in the dark?)
Author: nls

Mitch, I ran a "test" (we'll call it that, because it sounds better than 'I forgot to turn the IS off') tonight to see if what I mentioned earlier about the IS is really true. Here's a few full frame crops of the two shots:

With IS Off:

http://www.flickr.com/photos/nicksuydam/1435248945/

With IS On:

http://www.flickr.com/photos/nicksuydam/1435248819/

Quite a difference, I wasn't expecting it to be that bad!

Nick S.

http://www.nicksuydam.com



Date: 09/24/07 19:35
Re: A shot in the dark (how to focus in the dark?)
Author: Mgoldman

Wow - that's insane.

I read about it being an issue with the Nikon VR but never heard
anything about it being an issue with Canon's IS.

My results with /without were not as drastic but certainly evident.

Thanks for sharing the results.

(To those at the Bel-Del night shot - I'm not insane!)



Date: 09/26/07 02:40
Re: A shot in the dark (how to focus in the dark?)
Author: MrMRL

That Canon IS issue is interesting, and news to me. I will have to check this out in the future. Thanks for bringing it up!

Mr. MRL - Canon S2 IS



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