focus at infinity?


Status
Not open for further replies.

phantasia

New Member
Nov 9, 2003
639
0
0
The North
Visit site
#1
Hihi!

I knoe that focus at infinity is for far away objects...such as landscapes? But in wat situation can you actually use focus at infinity? As in how far is considered far?

Suppose i haf a tree 5m in front of me...does it make a difference if i focus on the tree...or i focus to infinity?

I'm oso thinking more of concerts...suppose i haf a cam which haf difficulty focussing in low lights...can i just set it to focus to infinity all the time and just shoot without bothering bout focus lock?

Thanks!!! :p
 

clive

Senior Member
Oct 9, 2002
2,537
0
0
Visit site
#2
usually more anything at 30m or more from u is taken as "at infinity" ^_^
 

justarius

Senior Member
Nov 9, 2003
1,226
0
36
Northeast
Visit site
#3
Sorry, chup in a bit... :D

How does hyperfocal focussing differ from focussing at infinity? Is the depth of field larger when using hyperfocussing techniques than simply focussing at infinity?

Thanks!
 

clive

Senior Member
Oct 9, 2002
2,537
0
0
Visit site
#4
there are detailed arguments that conclude that hyperfocussign gives u the maximum range of DOF, there are other studies that claim other wise...actually even if thay are correct to any extent, well our eyes wont really see much diff unless u intend to be very very meticulous (which i dont recommend, due to a pragmatic and time saving point of view ), it like the issue with DOF preview: press the button and the aperture blades stop down, viewfinder gets so dim that u cant even really see clearly, let alone judge the range of DOF that u want to be accdeptable...so, at the end fo the day, it really really doesnt matter loh (well, there r better thingsd to do, like swimming! ;-) ^_^
 

Kit

Senior Member
Jan 19, 2002
11,698
42
48
42
Upper Bukit Timah
Visit site
#5
A simple explaination. Hyperfocal focussing does not focus at infinity. It focuses on a spot some in front of the camera to give good DOF for foreground objects but at the same time, the background is still in focus. E.g. on a Canon 20mm f/2.8, when using f/8, the hyperfocal distance would be around 1m and anything in front of your camera that falls within the range of 0.7m to infinity would be in focus.
 

Kit

Senior Member
Jan 19, 2002
11,698
42
48
42
Upper Bukit Timah
Visit site
#6
Hyperfocal focussing is useful as you can preset the lens focus for fast snapshots as long as you can the object distance fairly accurately. Try it on scenes with layers(with foreground and background). Compare the shots focussed at infinity, you'll definitely see the difference, even with DOF preview.
 

justarius

Senior Member
Nov 9, 2003
1,226
0
36
Northeast
Visit site
#7
Ah, thanks for the explanations! So hyperfocussing will get you more foreground DOF as compared to focussing at infinity right?

I find that my eyes aren't very sharp...when stopping down in DOF preview, things which I think are in focus aren't...so trying to get a way to ensure sharpness when I need it and not on the camera's AF. Thanks! :D
 

Kit

Senior Member
Jan 19, 2002
11,698
42
48
42
Upper Bukit Timah
Visit site
#8
If you use hyperfocal focussing and know your lenses well enough, you don't even have to use DOF preview anymore. :) Just compose and shoot. If want to be a bit more kiasu, focus with a smaller aperture mark than the aperture you're using. E.g. if you're using f8 to shoot, focus using say..... the f11 mark on the lens.
 

justarius

Senior Member
Nov 9, 2003
1,226
0
36
Northeast
Visit site
#9
I see I see...so I basically have to make sure that I'm within the hyperfocussing distance and just shoot lar? Thanks! :D
 

Kit

Senior Member
Jan 19, 2002
11,698
42
48
42
Upper Bukit Timah
Visit site
#10
Hmm...... first you have to decide how far is your foreground objects is roughly. That will help you select the appropriate aperture. If you want to play safe, focus using the aperture that is a stop smaller than the chosen aperture to take the picture. So the aperture you use to shoot and the aperture mark on the lens you use to focus is different.
 

justarius

Senior Member
Nov 9, 2003
1,226
0
36
Northeast
Visit site
#11
hmm..guess I have to test it out soon. Being a film shooter, this sort of blurness issue very gek sim when you see your attempted 'artistic' shots going haywire cos it's out of focus...

Thanks!
 

mikedsjr

New Member
Mar 17, 2004
7
0
0
#13
Kit said:
A simple explaination. Hyperfocal focussing does not focus at infinity. It focuses on a spot some in front of the camera to give good DOF for foreground objects but at the same time, the background is still in focus. E.g. on a Canon 20mm f/2.8, when using f/8, the hyperfocal distance would be around 1m and anything in front of your camera that falls within the range of 0.7m to infinity would be in focus.
Does hyperfocus work on all lenses?
 

Jia Wang

New Member
Feb 20, 2004
1,306
0
0
43
Starry Night
www.pbase.com
#14
phantasia said:
Hihi!

I knoe that focus at infinity is for far away objects...such as landscapes? But in wat situation can you actually use focus at infinity? As in how far is considered far?

Suppose i haf a tree 5m in front of me...does it make a difference if i focus on the tree...or i focus to infinity?

I'm oso thinking more of concerts...suppose i haf a cam which haf difficulty focussing in low lights...can i just set it to focus to infinity all the time and just shoot without bothering bout focus lock?

Thanks!!! :p
The only time I focused at infinity was for the following shot of the heavenly stars which I took up in a mountain in Nepal... Exposed the film for 13 mins, aperture at f3.5, in almost total darkness (and cold) late at night...

 

justarius

Senior Member
Nov 9, 2003
1,226
0
36
Northeast
Visit site
#15
Cool! :thumbsup: :thumbsup: But it looks a bit shaky (as in the star trails aren't truly circular...)

mikedsjr: I believe hyperfocussing techniques can be used on all lenses, but most modern zoom lenses does not provide a DOF scale on the lens, making it hard to use this technique.
 

justarius

Senior Member
Nov 9, 2003
1,226
0
36
Northeast
Visit site
#17
kex said:
most,if not all NIKON lens have HF marking.
Erm, my 28-80G and 75-240D doesn't, but my 3 primes does. I don't know about the higher end zoom lens though. Guess I should change my statment to 'some modern zoom lens lack DOF markings..' :D
 

zod

New Member
Mar 30, 2003
1,279
0
0
#18
what's hyperfocal focussing???
 

Jed

Senior Member
Jan 19, 2002
3,911
0
0
UK
Visit site
#19
clive said:
usually more anything at 30m or more from u is taken as "at infinity" ^_^
Doubt that. Depends completely on what lens and what aperture you're using. With a 400mm lens at f2.8 for instance, your DOF at 30m is only from 29.5m to 30.5m. Easy to see that if you just focus at infinity, something just 32m away won't be in focus. Stopping down to f5.6 changes that to 29.1m to 31m in focus, still not sharp enough.

I've explained this already before on this forum when some time ago at national day someone suggested shooting planes in flight just by focusing at infinity. Not going to work.
 

Cash

Deregistered
Jan 10, 2004
200
0
0
#20
phantasia said:
Hihi!

I knoe that focus at infinity is for far away objects...such as landscapes? But in wat situation can you actually use focus at infinity? As in how far is considered far?

Suppose i haf a tree 5m in front of me...does it make a difference if i focus on the tree...or i focus to infinity?

I'm oso thinking more of concerts...suppose i haf a cam which haf difficulty focussing in low lights...can i just set it to focus to infinity all the time and just shoot without bothering bout focus lock?

Thanks!!! :p
at 5m, focus at 5m. if not, use zone focussing to get apparent sharpness.
 

Status
Not open for further replies.
Top Bottom