Using F8 in a studio

donkeymusic

donkeymusic

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Carlo
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Morning,

When shooting in the studio i use F8 1/125 and iso 200.

Now i thought that using F8 would give me an acceptable depth of field, however today i was doing a shoot with two children, 6 month old boy and three year old girl. I had the boy data slightly on front of the girl and i was focusing o the boys face.the girls head at the time was probably no more than a foot away but appears to be very out of focus. Which i didn't expect.

Just looking for advice.

Thanks
 
F11, iso 400, or turn the flash up a stop, or use a 1.6 crop camera, or shorter focal length lens?

I regularly use f11 or even f16 when shooing more than one kid. The greater depth of field helps a lot because the little blighter's move about so focussing isnt so critical. The DoF is irrelevant because they are usually in front of a plain background. Lens aberrations (as the geeks will tell you) is supposed to ruin your images at that aperture, but I've got 24" and bigger prints tack sharp and are far less ruined than an image being out of focus.

You do need powerful lights however (400WS minimum or more) to do this and maintain your prime ISO, especially to keep any ratio between lights that you might be running, and if you're throwing it through a 2 or 3 stop reducing modifier. My main light is often an 1100 WS elinchrom, and it helps a great deal.
 
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Did you use a lightmeter? With 2 subjects especially kids where they move about you will possibly need a higher aperture. What focus settings did you have? Was it one af point or all of them?
 
I use f11 1/160 ISO 200

Pretty much always in focus whatever you do. Then change accordingly to gain or loose depth of field.
I have always found it best to use a smaller aperture and low iso. Then the light in the images is more or less all dictated by your control of the studio lights.
 
I also use 1/160" (safely under the radio trigger threshold) f/11 (as often in a light ambient surrounding), iso200 (base iso on D3) as a starting point.
Your recycle time and power capacity might influence what you can achieve, but I rarely have my 500R heads over 3/4 power so still good recycle time and power in reserve if needed
 
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<i thought that using F8 would give me an acceptable depth of field>
It depends on 1. the focal length of the lens you are using. 2. How far away you are from the point you are focusing on.
Then look up your depth of field tables to see if what you want is acheivable at that aperture. If not see what aperture is required to give the depth of field you want.
 
To those that mentioned it, Shutter speed is irrelevant in the studio. Doesn't matter if you use 1/60th, 1/125, 1/200th - The speed of the flash is your shutter speed.

Regards depth of field, this is related not only to the aperture but more so to the magnification of the subject on the sensor. Higher magnification means a MUCH shallower depth of field. So a longer focal length from the same camera position will give a shallower depth of field than a less magnified (wider focal length) image.

Gareth is pertty much saying that.
 
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EOS_JD said:
To those that mentioned it, Shutter speed is irrelevant in the studio. Doesn't matter if you use 1/60th, 1/125, 1/200th - The speed of the flash is your shutter speed.

Regards depth of field, this is related not only to the aperture but more so to the magnification of the subject on the sensor. Higher magnification means a MUCH shallower depth of field. So a longer focal length from the same camera position will give a shallower depth of field than a less magnified (wider focal length) image.

Gareth is pertty much saying that.
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Also, although this is perhaps just another way of saying the same thing, DOF is related not to the f/number but to the effective aperture of the lens. Effective aperture is the actual, physical size of the lens aperture.

Say you have a 100mm lens (F100)
and you're shooting at f/10. Divide the f/number (10) into F = 10mm.
Now, suppose that it's a 25mm lens. F25
And you're shooting at f/2.5. Divide the f/number (2.5) into F = 10mm.

So, the depth of field at f/25 on a 25mm lens is identical to that of f/10 on a 100mm lens or to f/5 on a 200mm lens or f/2.5 on a 400mm lens, etc.

The point is, just saying that f/8 should be enough isn't necessarily right, it depends on the focal length of the lens, because the effective aperture is what matters, not the f/number.
 
Garry Edwards said:
Also, although this is perhaps just another way of saying the same thing, DOF is related not to the f/number but to the effective aperture of the lens. Effective aperture is the actual, physical size of the lens aperture.

Say you have a 100mm lens (F100)
and you're shooting at f/10. Divide the f/number (10) into F = 10mm.
Now, suppose that it's a 25mm lens. F25
And you're shooting at f/2.5. Divide the f/number (2.5) into F = 10mm.

So, the depth of field at f/25 on a 25mm lens is identical to that of f/10 on a 100mm lens or to f/5 on a 200mm lens or f/2.5 on a 400mm lens, etc.

The point is, just saying that f/8 should be enough isn't necessarily right, it depends on the focal length of the lens, because the effective aperture is what matters, not the f/number.
Click to expand...

Gary, technically it's magnification you are talking about. What you describe above would only hold true if the subject is the same magnification (same size on the sensor) in each scenario. Magnification is made up of both focal length and distance to subject.
 
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EOS_JD said:
Gary, technically it's magnification you are talking about. What you describe above would only hold true if the subject is the same magnification (same size on the sensor) in each scenario. Magnification is made up of both focal length and distance to subject.
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Effectively, yes - but my point is that people need to be aware that f/ is no more than a formula that doesn't in itself guarantee that there will be the amount of DOF that they are looking for. For example, they can't say that at a distance of 10' the DOF at f/8 will be X with my camera, but they can say that at a distance of 10' the DOF at 5mm aperture will be X
 
Garry Edwards said:
Effectively, yes - but my point is that people need to be aware that f/ is no more than a formula that doesn't in itself guarantee that there will be the amount of DOF that they are looking for. For example, they can't say that at a distance of 10' the DOF at f/8 will be X with my camera, but they can say that at a distance of 10' the DOF at 5mm aperture will be X
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Why not?

It should be quite simple to work out the dof these days as pretty much any smartphone will have a simple application to providxe that now Garry.

Can you explain again your workings for dof as in the previous post you just mentioned aperture and focal length but not distance (which is a major part of the equation as f/l and distance to subject make up the magnification part.
 
Not forgetting that DoF is only relevant when printing out - and it depends how big you print out (and how far away you view it) as to how deep the DoF is.
 
EOS_JD said:
Why not?

It should be quite simple to work out the dof these days as pretty much any smartphone will have a simple application to providxe that now Garry.

Can you explain again your workings for dof as in the previous post you just mentioned aperture and focal length but not distance (which is a major part of the equation as f/l and distance to subject make up the magnification part.
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I'm not sure that there is really anything to explain here, the point that I'm trying to make is that the aperture part of DOF is controlled by the effective aperture and not by the f/number, which are not the same thing - I think that a lot of people think that f/8 is f/8 is f/8... and don't realise that f/ is just an expression of focal length divided by effective aperture.
And yes, magnification/distance are other important parts of the equasion.

Not forgetting that DoF is only relevant when printing out - and it depends how big you print out (and how far away you view it) as to how deep the DoF is.
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That isn't right. Magnification/image size/viewing distance are all very relevant regardless of whether it's a print, an image on a webpage or on the camera monitor. It's just that unsharpness shows up more in larger prints/magnifications/shorter viewing distances.

The important part here is that DOF is subjective, based on assumptions based on viewing distance, circle of confusion and on what is 'acceptable' to the viewer, the objective (and theoretically correct) approach is to say that an image is only sharp at the point of focus, everything else is unsharp to a greater or lesser extent - which comes back to the OP, saying that his shots are out of focus - which really means is that they are not acceptable to him, because part of any image on a different plane to the point of focus are always out of focus, unless of course you use the scheimflugg principle to shift the plane of sharp focus, on a suitable camera.
 
Before this all gets out of hand....can the OP show us a pic? Pixelate the features if they are sensitive images - we should be able to figure it out from hair.
 
Garry Edwards said:
That isn't right. Magnification/image size/viewing distance are all very relevant regardless of whether it's a print, an image on a webpage or on the camera monitor. It's just that unsharpness shows up more in larger prints/magnifications/shorter viewing distances.
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We agree with each other Garry ;) I usually use the word rendering the image but was lazy this morning and used printing.

The problem most people have is accepting that DoF is a perceived thing, not something that is defined when you take the image. As you mention, the thing to understand is that a lens is only completely in focus at one distance - anything closer or further away is out of focus - even if only a few millimetres. Having said that, the rate at which focus changes is determined by focal length, aperture and subject distance. Whether you perceive something as out of focus is determined simply by how big you render the image and from what distance you view it. View it big enough and anything that is off the focal distance will appear to be out of focus. Conversely, view it very small and from a long way away and everything will appear sharp!
 
Garry Edwards said:
I'm not sure that there is really anything to explain here, the point that I'm trying to make is that the aperture part of DOF is controlled by the effective aperture and not by the f/number, which are not the same thing - I think that a lot of people think that f/8 is f/8 is f/8... and don't realise that f/ is just an expression of focal length divided by effective aperture.
Click to expand...

I see Garry sorry I didn't read the point right then.
 
f25 on a 25mm lens is the same as f10 on a 100mm lens....are you sure?

You are now saying a wide angle lens stopped down has as little depth of field as a slight telephoto on a less stopped down aperture. OR did you miss out a decimal point? As it reads, it is rubbish. If you MEANT f2.5 on a 25mm lens, then I agree.

Accuracy is important, some people would have taken what you wrote as gospel and spouted rubbish for ever more.
 
Simon, I actually think Garry is right. In each scenario the subject would need to have the same MAGNIFICATION on the sensor

So that means that at the same magnification the 25mm lens would need to be much closer to the subject than the 100mm lens.
 
What a load of cobblers being written in that other thread.

The whole reason f/ is expressed as an f stop is so that the ratio remains constant to allow in the same amount of light.

f8 IS f8 regardless of which lens you use. The difference between f8 on a wide angle lens and f8 on a telephoto will be how close you need to be to get the same size subject - but THE LIGHT REACHING THE FILM PLANE WILL BE THE SAME. (Sorry, I still have a film plane, it just happens to be electronic nowadays). In order to keep the amount of light striking it the same at the same aperture, the size of the hole changes - long teplephoto needs a bigger hole to keep the ratio the same as a wide lens at the same aperture.

f-stop NUMBER remains the same. Actual hole in diaphragm changes to suit that f stop for the focal length.

Set your lights up for f8 and use whatever lens you like at f8 and the exposure will be the same. Light fall off in corners due to wide angles and light coverage notwithstanding - main subject covered by lighting.
 
That makes sense Simon.

I think the issue is that the OP wasn't getting enough dof at f8.
 
Lensflare said:
f25 on a 25mm lens is the same as f10 on a 100mm lens....are you sure?

You are now saying a wide angle lens stopped down has as little depth of field as a slight telephoto on a less stopped down aperture. OR did you miss out a decimal point? As it reads, it is rubbish. If you MEANT f2.5 on a 25mm lens, then I agree.

Accuracy is important, some people would have taken what you wrote as gospel and spouted rubbish for ever more.
Click to expand...
Yes, a decimal point escaped:eek:
I meant f/2.5
 
You said f2.5 @400mm - How can they both be that?
 
Yes, that's some of the theory.

Anybody else want to see pictures so we can maybe help?
 
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