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02-20-2021, 09:44 PM - 1 Like   #1
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my thoughts on lossless equivalencies that help me think about my composition

Equivalence is used as a shortcut to use different lenses in different formats to get what you, or someone else, already did without having to think about. A jpg shrinks total information and destroys the rest. A raw keeps the information but makes you input what to do with it, called the creative process of developing your photo. Well there are ways of thinking about what is equivalent due to optics in easy general ideas that allow you to build up a photo and it can even build a photo to look like one that has already been done but you will understand what has been done. That information wasn't thrown away.

Here are the 2 main things.
1) Frame a subject the way you like at whatever fstop you like and no matter what lens you use it will have the same area in focus.
2)However far away you are from the subject to get that framing, the surrounding background will twice as big as the subject the same distance away from the subject as you are.
This does have implications but start with that.

Of course everyone talks about the bokeh. Here is the thing about bokeh. If you worry about bokeh you quit caring about what is in your background by default. the reason is you either have to move your background twice as far back or forward to get the same background. (see 2 above) So if you already don't care about the background just move your subject farther away from what ever is behind.

Now the corollary for the background. If you frame with a 100mm at 11m the background at 11m is 2x the subject frame and the 200mm would be 2x at 22m but at half that distance just 1x How convenient that distance is 11m. meaning the background for 100 at a given distance is twice the background for the 200mm at the same distance.

Now go learn one lens well on your system. Look at your subject and figure out how big a frame you should use. Now think about how much background you want around the subject. You should already know how much will be in focus because it is the same for any lens and just a little bigger for a different format. You learned one lens so you know how far away you need to be and how much background that will give you. If you want half the background use a 2x focal length. If you want twice the background use 1/2x the focal length.

You have composed the picture before you even had the camera in your hands. You could have used the format equivalence to figure out the lens to get a look and copied it but there was little of you in the creating process, you were not present for that part.

and think about that bokeh a little more. If the background is smaller it has to expand to fill the sensor. Just like zooming in on the back of your camera, things get blurrier. If you expand beofre taking a picture or expand after on the back of your camera it looks blurrier.

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02-21-2021, 12:28 AM   #2
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QuoteOriginally posted by swanlefitte Quote
and think about that bokeh a little more. If the background is smaller it has to expand to fill the sensor. Just like zooming in on the back of your camera, things get blurrier. If you expand beofre taking a picture or expand after on the back of your camera it looks blurrier.
and what if the background is the foreground?
02-21-2021, 03:00 AM   #3
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QuoteOriginally posted by swanlefitte Quote
A jpg shrinks total information and destroys the rest. A raw keeps the information but makes you input what to do with it, called the creative process of developing your photo
But when you produce a .jpg from your raw file, are you not "shrinks total information and destroys the rest" also ?

Regards composition, you also need to take account of perspective. The further away you stand from your subject, the more the background and subject will appear to move closer to each other.
02-21-2021, 10:00 AM   #4
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I'm not sure what you're saying. But my Fuji GSW690III has a fixed 65mm lens. Its equivalence is 28mm on your small format camera. I do not think about what someone else already did with their 28mm when I take a picture. And the equivalent FOV of that 65mm will not have the same look and feel as a 28mm on a small format camera. Two different lens brands of the same format and focal length can have completely different bokeh. That's an inherent property of a lens design.

02-21-2021, 11:33 AM   #5
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QuoteOriginally posted by tuco Quote
I do not think about what someone else already did with their 28mm when I take a picture. And the equivalent FOV of that 65mm will not have the same look and feel as a 28mm on a small format camera. Two different lens brands of the same format and focal length can have completely different bokeh. That's an inherent property of a lens design.
That is what I am getting at. Certainly don't think about what somebody took at 28mn or 65mm, think about what you want to achieve.
And the difference between a 6 blade straight vs a 9 blade rounded aperture calls you to think about what you want to create.
02-21-2021, 11:51 AM   #6
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QuoteOriginally posted by pschlute Quote
But when you produce a .jpg from your raw file, are you not "shrinks total information and destroys the rest" also ?

Regards composition, you also need to take account of perspective. The further away you stand from your subject, the more the background and subject will appear to move closer to each other.
On the first point, i struggled for how to state this and retain the information I wanted to convey in as short a way as possible.

With perspective you have 2 parts. You point out the subject to background. There is also subject elements like nose to eyes. The latter should be apparent if you learn one lens well. The background perspective should become apparent when you know that 2x lens takes 2x distance so 1/2 the background in the same amount of picture. If you see 3 cows instead of 5 cows around your subject in your photo they are bigger. Perspective tells us a cow gets smaller the farther away it is. I see this information included in what I am saying.
02-21-2021, 11:53 AM   #7
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QuoteOriginally posted by biz-engineer Quote
and what if the background is the foreground?
Still works.
02-21-2021, 01:10 PM   #8
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QuoteOriginally posted by swanlefitte Quote
On the first point, i struggled for how to state this and retain the information I wanted to convey in as short a way as possible.
Take your time. I don't have a busy diary at the moment.

QuoteOriginally posted by swanlefitte Quote
Perspective tells us a cow gets smaller the farther away it is. I see this information included in what I am saying

I disagree. You are describing magnification, not perspective. If a cow gets smaller, then so too does a background object. But this is not perspective. Perspective is the relationship between two or more elements in a scene, separated by distance relative to the camera. They can appear close to each other, or far from each other, depending ONLY on the distance between the objects, AND the distance from the subjects to the camera.


Last edited by pschlute; 02-21-2021 at 01:36 PM.
02-21-2021, 02:29 PM - 1 Like   #9
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QuoteOriginally posted by pschlute Quote
I don't have a busy diary at the moment.
So it's not just me then?
02-21-2021, 05:27 PM   #10
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QuoteOriginally posted by pschlute Quote
You are describing magnification, not perspective. If a cow gets smaller, then so too does a background object. But this is not perspective. Perspective is the relationship between two or more elements in a scene, separated by distance relative to the camera. They can appear close to each other, or far from each other, depending ONLY on the distance between the objects, AND the distance from the subjects to the camera.
In this gif there is a 3' wide tv close to 5' back which will cover the frame with a 35mm lens on my apsc sensor. The model is 2.5' away, half way between. The shift is to a 70mm lens and moving back another 2.5'. The model stays the same size. The tv gets bigger. You can see the whole frame and then a smaller part of the frame bigger. The tv, and thus cows are flat so the perspective is completely in the magnification. of course my placement wasn't exact. but I move twice as far back and the cows grow by half thus giving a perspective of being closer.

Edit: I did the Spinal Tap, Stonehenge of using inches instead of feet. 3", 3'
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Last edited by swanlefitte; 02-22-2021 at 04:00 PM.
02-22-2021, 09:34 PM   #11
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Looking at the gif we see all the interesting stuff has nothing to do with equivalence.
How does the 's' in 'cows' appear from behind the model?
At the bottom half of the photo you see a 3d of the model become 3d vs flat. That deals with the sine/cosine function of the angle looking down(perpendicular) vs looking across ( parallel) to the object. IE, look straight at the edge of a board and you see the edge, look down and you see the top.
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