Focus to infinity?

onform

onform

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matt
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Hello

I generally take portrait and urban photo's but today as I have the day off work to look after my boys, the missus is off celebrating a certain saints day in london! I would like to turn my hand to a little landscape and maybe even a panorama. I dont have anything particularly interesting locally so I will concentrate purely on technical side of things.. maybe i will get something good who knows. :lol:

My Q is if i set my manual focus to infinity will this give me optimum focus across the image? I will use a high/small aperture and lowest iso.

I have until the littlest boy wakes up before i leave so if anyone who has an insight into this could help me out that would be great.. :wave:

Matt
 
If you use a small aperture the lens will give a large depth of field so focusing on just before infinity will give you an overall better optimum focus area.

There maybe some marks on your lens that will indicate the distances that will be in focus for a given aperture. The old fashion manual lens always had coloured lines to show this more clearly.
 
Do you mean like these? if i'm at 24mm focal length do i line up the infinty mark on the `white line or the red 24?? I seem to remember reading that the numbers in red are for infra red...is this correct???

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That's a strange looking scale. The old lenses mentioned normally have a line in the middle liek yours and then aperture numbers repeated left and right of it. You then use these markings along with your chosen aperture to see how much DOF you have. But this was from the days before firing test shots and chimping. I'm not sure if you cloud use the scale on that lens for a simliar thing as it has the focal length rather than aperture marked on the scale.
 
The red markings are the infrared focussing line-up marks at different focal lengths, so unless you are using IR film, ignore them and use the big white line in the middle!

Generally the most effective landscape photos have some good foreground interest, so focussing on infinity may not be best as it will probably put the foreground out of focus (depending on what aperture you're using). Some lenses have hyperfocal markings which show what range of distances will be in focus at a given aperture (like Kev M describes), but that's a bit of a black art as it's only an estimate based on a certain size of final enlargement of the image, and a few other compromises! However it is true that focussing just back from infinity and setting a small aperture (like f16 for example) will give you a very good range of subject in focus (depth of field). You may need to use a tripod though as a small aperture will necessitate a longer shutter speed. On a sunny day like today (where I am at least!) you can get away with hand holding as exposures will be something around 1/125 s at f16 using ISO 100 (known as the "sunny 16 rule").

Hope that helps and isn't just making it more confusing :nuts::lol:
 
onform said:
My Q is if i set my manual focus to infinity will this give me optimum focus across the image? I will use a high/small aperture and lowest iso.
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Doing that will give you a large depth of field but not the largest possible. What you need is to focus at the Hyperfocal Distance, this will give you the maximum possible depth of field. Using the hyperfocal distance can also allow you to get a large DoF with a wider aperture - for example approximately the same DoF can be achieved with f/8 at the HD as using f/16 focussed at infinity.
 
If you search for "hyperfocal distance " on here you will probably find some tables showing what and where the HD is at various focal lengths and apertures.

Actually using it is difficult because zoom lenses don't have depth of field scales on the barrel, but you can "guesstimate"; being an old film user I still use the depth of field preview button on my camera to show me what's in focus and what's not. But these days, as suggested, you can snap away and check your images on the LCD to see how sharp your image is.
 
I was advised some time ago that as todays digital only lenses (ie can't use on film cameras) do not have hyperfocal distances on them, just look through the viewfinder and pick a spot about one third into the scene and focus there. As long as you are on f11-16 this should be fine. I was also told don't go above f16 as you start to get image degredation due to some funny physics stuff (can't remember what it was called).

:)
 
photostar_1 said:
I was advised some time ago that as todays digital only lenses (ie can't use on film cameras) do not have hyperfocal distances on them, just look through the viewfinder and pick a spot about one third into the scene and focus there. As long as you are on f11-16 this should be fine. I was also told don't go above f16 as you start to get image degredation due to some funny physics stuff (can't remember what it was called).

:)
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The hyperfolal distance is not "on" the lens therefore you were advised wrong. What you may encounter is some lenses don't have a distance scale therefore it is hard to judge the distance.

The one third rule is a very loose rule, its much better to read and understand hyperfocal distance.

You get degradation after about f11, f8-11 is normally best but it does vary between lenses.
 
photostar_1 said:
.... I was also told don't go above f16 as you start to get image degredation due to some funny physics stuff (can't remember what it was called).

:)
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It's called diffraction, and it gets more pronounced the smaller the aperture you use. After a certain aperture, going smaller just creates more diffraction effects that make the resolving power of the lens worse - this is called the diffraction limit of the lens and varies depending on lens and camera design.

wikipedia has a good long page on diffraction if you're interested :D
 
Dont be put off going above f8-f11 i have read some great stuff on photographers who regulaly shoot f22. I will have a search through my notes and come back with a few names
 
Studio16 said:
Dont be put off going above f8-f11 i have read some great stuff on photographers who regulaly shoot f22. I will have a search through my notes and come back with a few names
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I used to shoot regularly at f45 with great results, but that was with large-format Schneider lenses on a 5x4 film camera! Anything above about f11 on a small-sensor digital compact is going to be diffraction limited. Matt (the OP) has a Canon 5D with L-series lenses so he'd be hard-pressed to notice any problems up to f22 and probably f32.
 
photostar_1 said:
I was advised some time ago that as todays digital only lenses (ie can't use on film cameras) do not have hyperfocal distances on them, just look through the viewfinder and pick a spot about one third into the scene and focus there. As long as you are on f11-16 this should be fine. I was also told don't go above f16 as you start to get image degredation due to some funny physics stuff (can't remember what it was called).

:)
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Just a reminder that it's zoom lenses which don't have depth of field scales on them.

It's not a film vs. digital thing....
 
One small question I have is that with regards to Nikon zooms (or rather, more specifically, the 18-200mm/5.6) on a similar tangent:

The focussing ring goes all the way up until the (gold) line lines up with the Left most side of the infinity symbol.

I assume that this is counted as the 'maximum infinity' and that even if the line is set to what I would assume to be the infinity point normally (the middle of the symbol) that this is focussing on less than infinity



(unless somehow this is some new mega awesome AF-S spec extra that actually makes a lens focus past infinity and in to the next dimension)
 
jerry12953 said:
Just a reminder that it's zoom lenses which don't have depth of field scales on them.

It's not a film vs. digital thing....
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Zooms do have distance scales! There's even a picture of one above!!!

Its is only a few of the more budget lenses that do not, its not a full vs crop or a prime vs zoom divide
 
photostar_1 said:
I was also told don't go above f16 as you start to get image degredation due to some funny physics stuff (can't remember what it was called).
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Diffraction.

As has been suggested earlier, look up hyperfocal distance. If you focus at infinity then you are wasting half of the in focus range of your lens.

For every focal length of lens there is a hyperfocal distance for every f stop.

When set to that distance everything from half that distance to infinity will be in focus.

e.g. If the hyperfocal distance for a particular focal length is given as 11' at f16 then everything from 5' 6" to infinity will be in focus.

If you have an older style lens with depth of field scales, line up the infinity mark at the aperture setting used and at the position of the other mark of the same aperture will be indicated the close distance which will be in focus.



Steve.
 
DavePaliwoda said:
One small question I have is that with regards to Nikon zooms (or rather, more specifically, the 18-200mm/5.6) on a similar tangent:

The focussing ring goes all the way up until the (gold) line lines up with the Left most side of the infinity symbol.

I assume that this is counted as the 'maximum infinity' and that even if the line is set to what I would assume to be the infinity point normally (the middle of the symbol) that this is focussing on less than infinity



(unless somehow this is some new mega awesome AF-S spec extra that actually makes a lens focus past infinity and in to the next dimension)
Click to expand...

Focusing beyond infinity is quite common, and not such a strange thing as it sounds! Temperature changes can cause very slight changes in focusing on some complex lenses, so to allow for that the manufacturers build-in a bit of flexibility at the infinity end to allow the camera AF to get the subject in focus. Of course this means that most of the time you can manually focus beyond infinity. All this means is that an object at infinity is not quite focused on the film/sensor plane - a bit like being long-sighted. The lens isn't "seeing into another dimension" :)
 
Well I never... there have been a few more replies since I left the house..lol any way I did manage to try and get a couple of photo's of a very boring featureless landscape but by the time I got to it a fine haze or bluey mist had blanketed the countryside just enough to make any shot illegible. Tried to get the layered shadow look but I just didn't have enough time to work it out... I guess that's what landscape is all about though knowing a location and keep going back till you get it just right weather and all..

Keep up the interesting replies though as they make interesting reading for me.
 
Uneducated_Rick said:
Zooms do have distance scales! There's even a picture of one above!!!
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On that 24-70 zoom? That's not a DOF scale Rick, those are infra red focusing marks, as I'm sure someone explained earlier. ;)
 
CT said:
On that 24-70 zoom? That's not a DOF scale Rick, those are infra red focusing marks, as I'm sure someone explained earlier. ;)
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I think he means the metres/feet numbers in the window to the left of the infinity symbol. Either way i'm not quite sure how it works,,,lol some more reading up i suppose. :lol:
 
That is a distance scale so I was correct, but the preivous post did say DoF scale :whistling: shouldn't speed read other responses.
 
onform said:
I think he means the metres/feet numbers in the window to the left of the infinity symbol. Either way i'm not quite sure how it works,,,lol some more reading up i suppose. :lol:
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Well the infra red marks aren't something you need to be worrying about at this stage, but it's not that complicated, so we may as well deal with it.

If you chose to put that lens on a film camera loaded with infra red film that's when those marks would be needed. Infra red light, which is what infra red film records, has a different wave length to 'normal' light. What this means in practice, is that you'd look through the viewfinder and focus as usual, then check the distance scale on the lens to see at what distance you've focused. Whatever that distance is, it will be aligned with the white focusing mark. You now need to shift the focus point to compensate for the infra red lights wave length.

To do that you just twist the lens focusing collar to re-align the focus distance with the red mark which corresponds with the focal length at which you're using the zoom. As you can see it's a slight adjustment at 70mm but gets larger as the focal length decreases.
 
Uneducated_Rick said:
That is a distance scale so I was correct, but the preivous post did say DoF scale :whistling: shouldn't speed read other responses.
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There aren't many lenses in Canon's EF range that have true DoF scales. None of the zooms do as they would need to change with focal length, and even the primes only have a minimal pair of marks for a single aperture (of the lenses I own at least). The only Canon lens I've got with a proper set is my 24TSE which is manual focus only. Other MF lenses have them, but I'm not sure about other manufacturers' AF lenses - perhaps a Nikon owner could enlighten us?
 
CT said:
...
If you chose to put that lens on a film camera loaded with infra red film that's when those marks would be needed. Infra red light, which is what infra red film records, has a different wave length to 'normal' light. What this means in practice, is that you'd look through the viewfinder and focus as usual, then check the distance scale on the lens to see at what distance you've focused. Whatever that distance is, it will be aligned with the white focusing mark. You now need to shift the focus point to compensate for the infra red lights wave length.

To do that you just twist the lens focusing collar to re-align the focus distance with the red mark which corresponds with the focal length at which you're using the zoom. As you can see it's a slight adjustment at 70mm but gets larger as the focal length decreases.
Click to expand...

You can do IR photography with digital camera as well. Most DSLRs have at least some IR sensitivity, so you get some interesting results using an IR-pass filter that blocks visible light. Exposure times often have to be very long but it's a fun technique to try!
 
So according to the on-line depth of field calculator... at 24mm on full frame camera and f16 if I focus my camera 122.4 cm away everything from 62.4cm to as far as the eye can see will be in focus???? I think I need to take a tape measure with me next time lol..
 
So according to the on-line depth of field calculator... at 24mm on full frame camera and f16 if I focus my camera 122.4 cm away everything from 62.4cm to as far as the eye can see will be in focus???? I think I need to take a tape measure with me next time lol..
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Not exactly, everything will be in 'ACCEPTABLE' focus. The question then is acceptable to who? Ive found unless you require close up focus ie. pebbles in a stream then focus a third into the frame or what is more important.
 
dcash29 said:
Not exactly, everything will be in 'ACCEPTABLE' focus. The question then is acceptable to who? Ive found unless you require close up focus ie. pebbles in a stream then focus a third into the frame or what is more important.
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Depending what you enter your C of C as, so the DOF will change. Focussing a third into the shot does not take this into account.
 
try to keep your measurements in meters and millimeters. Not like those penis gobblers and there love of feet and inch`s.
 
oldfella said:
try to keep your measurements in meters and millimeters. Not like those penis gobblers and there love of feet and inch`s.
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A better idea would be to use whichever system you feel more comfortable with. Especially if you need to estimate distance.

And it's inches, not inch's.


Steve.
 
Metric's for people who think 203.2mm sounds more impressive than 8 inches;)
 
snowy said:
Focusing beyond infinity is quite common, and not such a strange thing as it sounds! Temperature changes can cause very slight changes in focusing on some complex lenses, so to allow for that the manufacturers build-in a bit of flexibility at the infinity end to allow the camera AF to get the subject in focus. Of course this means that most of the time you can manually focus beyond infinity. All this means is that an object at infinity is not quite focused on the film/sensor plane - a bit like being long-sighted. The lens isn't "seeing into another dimension" :)
Click to expand...

Sweet-o, thanks!
 
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