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 Post subject: Want to know about those F-stops?
Unread postPosted: Thu Aug 18, 2005 10:13 am 
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Honorary Virtual Ranger
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Location: Red sand, why do I keep thinking of red sand?
F-stops are bothering you? Just read through this page while taking your time. Then go to sleep or work, whatever, come back and read it again. I think you will have figured it out then.

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 Post subject:
Unread postPosted: Thu Aug 18, 2005 1:16 pm 
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No figure..............

I am hoping I can stay awake long enough to get through the entire document. Not even to speak of reading it again.........

DvZ


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 Post subject:
Unread postPosted: Mon Feb 11, 2008 12:20 pm 
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Ok, beginner photographer talking here, so be patient with me. :P

What I'm understanding from this is:

The aperture of your camera is like an eye. The "hole" or "pupil" in the center allows light through. The bigger the "pupil" or hole opens, the more light is allowed through. Your F-stop determines how much the hole opens. Your shutter speed determines how fast the hole opens and closes.

The higher the f-stop, the smaller the opening of the aperture.
The smaller the fraction set by the shutter speed, the fast the photo takes and the faster the aperture opens and closes.

So,
1. If you are taking a shot at dusk, you would set a higher f-stop and slow shutter speed (and use a tripod to avoid camera shake!)

2. If you are taking a well-lit "easy" shot, you would use a low f-stop and fast shutter speed.

3. If you want movement blurring, lets say of a waterfall, but it was well-lit, you would use a high f-stop and a slowish shutter speed.
------------------------------
That's kind of what I gathered. Tell me if I'm on the right track. Its really sad... on my camera I have 3 f-stops: 2.4, 4.8 and 8.2. But I can't set my shutter speed. My camera is digital, so it likes to do things automatically by itself! xD Its very annoying when you are trying to purposefully get an effect like a glare or something.


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 Post subject:
Unread postPosted: Mon Feb 11, 2008 12:36 pm 
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Oh, one more thing I want to add:

The higher the f-stop, the more blurred the "background" of your picture is... That whole "clear focal point with blurred everything else" thing.

Well, that bit of info I've still been exploring with, but haven't mastered really.


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 Post subject:
Unread postPosted: Mon Feb 11, 2008 12:58 pm 
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Junior Virtual Ranger
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DQ .. go and visit www.outdoorphoto.co.za and you will find everything you need on this topic. You will also get a whole bunch of outdoor photographers who will be more than willing to help you with it.


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 Post subject:
Unread postPosted: Mon Feb 11, 2008 1:49 pm 
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Location: Red sand, why do I keep thinking of red sand?
Look in the memberlist there. :wink:

But Tzel has reminded me of a few photos I took while waiting for our ferry, with this topic in mind, look at the background, (and shuttertimes):

f/5.6 @ 1/400:
Image

f/10 @ 1/125:
Image

f/14 @ 1/60:
Image

The last photo is rather cluttered, the first is not really good either, but with the lens I used I can't go the the f/2.8 you really need for it. However you can see the effect of singling out the flowers from the background.

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 Post subject:
Unread postPosted: Mon Feb 11, 2008 8:24 pm 
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Tzel wrote:
Your shutter speed determines how fast the hole opens and closes.

The higher the f-stop, the smaller the opening of the aperture.
The smaller the fraction set by the shutter speed, the fast the photo takes and the faster the aperture opens and closes.

So,
1. If you are taking a shot at dusk, you would set a higher f-stop and slow shutter speed (and use a tripod to avoid camera shake!)

2. If you are taking a well-lit "easy" shot, you would use a low f-stop and fast shutter speed.

3. If you want movement blurring, lets say of a waterfall, but it was well-lit, you would use a high f-stop and a slowish shutter speed.
------------------------------


The faster the photo takes is due to shutter speed, not the speed your aperture opens, that just opens or closes to what you set it, speed is controlled by shutter speed.

Your number 1 and 2 are mixed up.
The will set a lower f-stop to get more shutter speed.
The smaller the f-stop the bigger the shutter speed at the same light.
For low light you want to use the camera with the aperture/iris fully open to let in more light, the more open it is, the lower the f-stop number, but you call it a bigger aperture/f-stop.

3 - correct .

Remember that there is only 1 correct shutter speed for a certain f-stop depending on the light available, you cant just set a f-stop and then set whatever shutter speed you want, as the two have to work together to create the correct exposure.
On my camera I just control my aperture(f-stop) , and see what shutter speed I get to see if that will work to stop blur(Or create it).

aperture/f-stop is primarily used to get different deapth of field, and this is its most important use to create a different look to your background focus.
DuQues photo examples highlight this nicely.


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 Post subject:
Unread postPosted: Wed Mar 26, 2008 8:07 am 
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Bucky said
Quote:
On my camera I just control my aperture(f-stop) , and see what shutter speed I get to see if that will work to stop blur(Or create it).


Bucky, what to do if the shutter speed does not take care of the blur?

Example:
You're at the 13th borehole KTP, first sunlight just falling on lion (drinking), and 2 cubs (playing) just in front of mom.

To get all in focus (DOF), I understand you need a higher f/stop? But with all the movement, you need a faster shutter speed, maybe 1/500?

But there is little light, so the camera "suggests" 1/50 or 1/100 = blurred images

What to do ?
Higher ISO
Zoom out, and crop later (I have a 100-400 Canon IS) - at this waterhole you are close enough, but what if subject is further away

Any advice appreciated, because I have messed up so many times in this type of situation :evil:

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 Post subject:
Unread postPosted: Wed Mar 26, 2008 9:20 am 
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I think you may be confusing the terms blur and out of focus.
blur is when either you move to much blurring the whole photo or the subject moves, blurring the part that is moving.
Out of focus is when your point of focus is incorrect, and this will blur everything in that focal plane.
So therefore you get two types of blur - motion or focus.

To try answer some of your questions -

Higher iso is a definite solution, even to push as far as 800 IF and that is IF your camera can handle that iso without looking like a noise experiment.
ISO 400 works pretty well though on most slr's.
Another thing is to make sure you are shooting with your camera on a bean bag or some sort of solid rest, this is the most important thing out.
Also be sure that when you press the shutter that you do not press it to hard.
In very low light I am as gentle as possible with my shutter press, and even hold my breath to stop the camera from moving, and have managed to create some good shots at super low shutter speeds by using this technique.

In low light I tend to open my lens fully up (Biggest aperture=smallest number value) and shoot to the circumstance, if there is not enough light to get all the animals in focus then tough luck.
Its no use trying to use f8 or f11 in low light to try get more things in focus, because you will movement blur the shot, either from your or the subjects movement.
A shot with only some parts in focus like the face will be usable, and in most cases look really good, but a shot where it is blurry because of camera movement is only good for the bin.
There is no way to have it all, and you need to go for a tight focus point in low light, and compose to suit this.
When there is a bit more light, then you can start going for more depth of field (More stuff in focus) with a higher aperture like f8 or f11 to get plenty of things in focus.
f8 is fine to get a whole medium sized animal into focus, a group or big things like ellies may well need f11.

My standard aperture settings unless I want something specific from a shot are F4/5.6@iso400 in the early morning, and then F8@iso200 during a bright day, or f8@iso400 on a cloudy day.
I will still drop to the lowest aperture sometimes if I want a more portrait sort of shot with lots of background blur(out of focus blur)
For a landscape I go to f11 on the shorter zooms of below 100mm and this gets all in focus.

The zoom length will not make any difference if an animal is moving, its just that with more zoom you will notice it easier.
The biggest thing with more zoom though, is that the longer your focal length, the more motion blur you will get with your own movement.
a shot taken at the same shutter speed at 20mm will not show blur as easily as a shot at 600mm.


Last edited by bucky on Wed Mar 26, 2008 10:15 am, edited 1 time in total.

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 Post subject:
Unread postPosted: Wed Mar 26, 2008 10:00 am 
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Bucky thank you so much for such an informative reply. I have definately learned a lot from your post.

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 Post subject:
Unread postPosted: Wed Mar 26, 2008 11:24 am 
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Thanks bucky for taking the time to reply in detail - it is making a lot more sense now. I think my problem is more subject movement, and then lack of depth of field. As you say, I may have to accept only one subject in focus in poor light.

While I can, just one more question - Am I right in thinking that, in low light conditions, it may be best to swtich off IS, rest the camera on a bean bag, allowing a lighter touch on the shutter press - or do I lose more than I gain this way.

Thanks
Peter

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 Post subject:
Unread postPosted: Wed Mar 26, 2008 11:43 am 
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That would all depend on how steady you are.

What a lot of experienced guys do, is to use IS in low light, then to shut it off during the day. They also use a bean bag or mount of sorts, IS should not be seen as a reason not to use a rest.

When people say you should turn IS off on a tripod or something, this does work to make shots even sharper, but with ample light.

If you want to turn IS off, then ideally you need a very solid tripod or rest and a remote shutter switch so you don't even touch the camera.


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Unread postPosted: Thu Mar 27, 2008 12:07 pm 
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Personally I only turn IS off under 2 circumstances. Lens is on a VERY sturdy tripod (beanbags though essential don't count as very steady!) - especially older lenses which apparently can be damaged with IS on and on tripod.

Secondly if battery almost dead and no where to recharge and no backup battery! IS does use extra power. But you really should not get into this mess in the first place!

Richard

ps ISO 1600 OK many DSLRs if you are prepared to use something like neat image, noise ninja etc. Can give very good results. The noise reduction in photoshop (any version / variety) is not nearly as good as these standalone programs.


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Unread postPosted: Thu Mar 27, 2008 3:11 pm 
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Thanks Bucky and Richard.

Still trying to get my mind around the role of the IS - I am trying to make a decision between the Canon 24-105L IS 4.0 and the 24-70L 2.8.

I am 90% wildlife photography, and the 100-400L IS handles just about everything very well, except landscapes and subjects close to the vehicle, so I am agonising over which of these two lenses as the solution. Also, the 100-400 is slow, not good in early morning /dusk.

Quote:
Image Stabilizer provides the ability to take a handheld shot at 3 stops less than your standard “non-IS” lens would be able to do


Hmmm... meaning a 3 stops smaller aperture? Allowing greater DOF? Less blur from shake? But no blur reduction if subject in motion. And shutter speed would need to be reduced?

So how important is IS in choosing between these two lenses for wildlife photography? Anybody had experience with both?

Really appreciate your thoughts and advice.

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Unread postPosted: Thu Mar 27, 2008 3:30 pm 
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F2.8 wins hands down.

Why - because it lets in double the amount of light .

Imagine a lion or leopard walking along the road next to you in early light, with the f2.8 you can perhaps get the shot, with the f4 maybe not.

Motion blur can only be countered with a big aperture like a f2.8 or a high iso resulting in loss of clarity.
Richard is quite right by saying that stand alone noise reduction programs can do good work, but the more noise that needs to be removed, the more sharpness and detail you loose, because those fine details in a picture tend to get "cleaned up".

That said, between those 2 lenses, the 24-70 is a finer lens, and is sharper than the 24-105.
The bigger the zoom, the bigger the loss in clarity.

The 24-105 is designed for people walking about doing say for instance weddings that need the versatility of 1 lens and IS because they hand hold a lot, if you think about it I reckon this lens was designed specifically for this purpose.

For a wildlife tog, you are generally shooting out of a car or a hide, so you always have the availability of a rest.
Consider also that the f2.8 will already give you 1 stop extra against shake, while the IS lens may give you two/three it is up to the electronics which may not be spot on.

In the smaller lenses as I mentioned earlier movement blur caused by the photographer is not as easy to see as with a zoom, but motion blur because of the subject will stay the same, so a faster f2.8 lens will make a difference.


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