Help converting exif details to 35mm equivalent please

Messiah Khan

Messiah Khan

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Alasdair Fowler
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Ive stumbled across some fashion/portrait shots that I love. I would love to attempt to do something similar so ive had a nosey at the exif data;

Orientation of image: 1
File change date and time: 2007:10:08 10:47:24
Image input equipment manufacturer: Leaf
Image input equipment model: Aptus 75
Software used: Adobe Photoshop CS3 Macintosh
Exposure time: 0.025
F number: 3.6
ISO speed rating: 100
Shutter speed: 5.32193
Aperture: 3.69599
Exposure bias: 0
Lens focal length: 0
Exposure mode: 1
Click to expand...

But as you can see, it was taken on a Leaf Aptus digital back. What I want to know, is how the increase in sensor size of a large format camera would affect the aperture? Ie, what does f3.6 on a large format system translate to on a DSLR?

Oh, and the pictures in questions are;
http://www.gusmarx.com/moda04.htm
Mainly picture 1 and 5
 
The aparure of a lens is independent of the camera it's used on. It relates to the physical diameter of the iris divided into the focal length. It's lens specific not camera. So the lens used on the Leaf Aptus back, if it could be fitted to your camera would still have the same aparture. F3.6 is still f3.6.

By the way the Aptus is a digital camera back, not a camera in itself. It can be fitted to a number of medium format cameras such as Hasselblad Bronica ect.

Try this link if you want some more information

http://www.leaf-photography.com/
 
Yep - f8 is f8 regardless of the actual size of the lens aperture. :)
 
Yeah I realise this. I should have been more clear. I was more referring to the dof that is achieved when using a certain aperture. So f3.6 on a Leaf Aptus back (48mmx36mm sensor size) gives say 10cm of focus at 2 metres distance from the subject. Is this the same for a DX sized sensor (23.7 x 15.7)? Or does the size of the sensor affect the dof acieved at a certain aperture?
 
You'll read that the smaller the sensor the greater DOF (at a given aperture) and whilst it's true it's very misleading if taken literally.

If we stood side by side photographing the same subject - you with a full frame sensor and I with a 1.6X crop sensor, you'd get the wider FOV, but DOF for both of us would be the same.

If however, I move back increasing the camera to subject distance until I'm getting the same field of view as your full frame sensor, then because the greater distance equals more DOF, I get more DOF than you, but it only applies when we're seeing the same field of view with both sensors.
 
The effective focal length of a lens will determine the DoF at a given aperture. It's all to do with a little thing called the Circle of Confusion. And it can be very confusing.

See http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/depth-of-field.html it might help.

In the good old days camera lenses came with depth of field indicators on them, even many zooms had this, I believe some Sigma lenses still do.

If you need to work out DoF then you could sit down with a calculator and work it out. You'll find the formulas out on the web. However I use a simple device called an expoaperture. You dial in the sensor size and focal length and it gives you the DoF at any aperture ( well between f1 and f64 )

So the longer the effective focal length the smaller the DoF at a given aperture

If it's any help with your original post I would bet that the camera format used is either 6 x 6 or 6 x4.5, so I would suspect he had limited depth of field on that shot
 
I thought the dof was to do with the magnification, not the focal length (Although the two are often linked)?
 
Yes, DoF is a function of magnification and aperture. But focal length also plays a part in defining the magnification - focus at 5m with a 100mm lens and a 300mm lens and clearly the 300mm will resolve a larger image.

This is also why macro lenses all have the same DoF at 1:1 regardless of focal length - they are all focused at a different distance which cancels out the difference in focal lengths.
 
I cant help with the question but god some of those models are skinny!:thumbsdown:
 
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