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08-24-2019, 12:25 AM   #226
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QuoteOriginally posted by Ian Stuart Forsyth Quote
So when you use the term equivalent exposure most people take that as meaning total light. Equivalent exposure is one that uses the same shutter speed and entrance pupil for there equivalent lenses with the same FOV.
So what your saying is as the OP in my original question I just miss spoke (used the wrong term) when I used the term "EQUIVALENT EXPOSURE" I should of said "get the same exposure"?
The term " EQUIVALENT EXPOSURE" refers to exposure (SS, ISO & F:stop) + FOV?

QuoteOriginally posted by Photobill Quote
Sample
I use a light meter and it says shoot the scene @ f2.4 Would I get approximately the same expo with a FF & APS-C body? Or would I need to open up to f:2 or f:1.8 on the APS-C to get the equivalent exposure as on a FF.



Last edited by Photobill; 08-24-2019 at 12:36 AM.
08-24-2019, 01:10 AM - 2 Likes   #227
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QuoteOriginally posted by Ian Stuart Forsyth Quote
Never did say that a light meter will give you a different exposure on different formats, however I have been saying all along that if you want to collect the same amount of light across different formats that you will need to use a different exposures for the different format sizes.
Well done. You get prize of the year for the answer most likely to confuse anyone asking a simple question about exposure. "collect the same amount of light" ...utter tosh.

---------- Post added 08-24-19 at 09:14 AM ----------

QuoteOriginally posted by Ian Stuart Forsyth Quote
To get the same exposure you would use the same ƒ/2.4 now to get the equivalent exposure ( as the more common used understanding) when most people that use the term equivalent exposure they are refereeing to total light
so on FF you will need to open up the lens to ƒ/1.6.
So when you use the term equivalent exposure most people take that as meaning total light. Equivalent exposure is one that uses the same shutter speed and entrance pupil for there equivalent lenses with the same FOV
More confusing babble. I have been on these forums for a number of years and have been taking photographs for even longer. Nobody talks about "total light" or "equivalent exposure" and means what you perceive it to mean.

---------- Post added 08-24-19 at 09:17 AM ----------

QuoteOriginally posted by Ian Stuart Forsyth Quote
Yes but as you just stated one will collect more light. of that light.
Are you sure the elves don't have torches ?

Last edited by pschlute; 08-24-2019 at 01:43 AM.
08-24-2019, 01:18 AM - 1 Like   #228
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QuoteOriginally posted by pschlute Quote
Well done. You get prize of the year for the answer most likely to confuse anyone asking a simple question about exposure. "collect the same amount of light" ...utter tosh.

---------- Post added 08-24-19 at 09:14 AM ----------





More confusing babble. I have been on these forums for a number of years and have been taking photographs for even longer. Nobody talks about "total light" or "equivalent exposure".

---------- Post added 08-24-19 at 09:17 AM ----------





Are you sure the elves don't have torches ?
I would've used a different term rhyming with 'bear pit', Peter, well done for your restraint!
08-24-2019, 01:20 AM   #229
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QuoteOriginally posted by pschlute Quote
The point is that pixels in an image file do not have a physical size.
Sure they doe have a physical size or I would not be able to photograph them
Here is the k7 Kind of look like they have a size too me




QuoteOriginally posted by pschlute Quote
It was you that brought pixel size into the discussion by claiming that every digital image required "huge magnification".
The magnification is the size difference between the image projected onto the sensor and how you ether view the image on the screen or whether you print it. it all comes from that projected image which has a size. you zoom in with your computer screen you are zooming in more on that projected image.








QuoteOriginally posted by Dartmoor Dave Quote
Please think very carefully about the important point that pschlute has stated far better and far more succinctly than I've done: Pixels in an image file do not have a physical size.
Now this next bit is going to blow your mind: a 16"x10.88" print from a 16 megapixel file is effectively a contact print. It's a print at 1:1 resolution, in which one pixel on the sensor equals one dot of ink on the print (told you it would blow your mind).
It can seem counterintuitive, which is why so many people prefer the comforting myths of equivalence, but when we're talking about digital photography the physical size of sensors and screens usually has very little to do with things. After all, your computer doesn't need to know the physical size of your monitor to display photos properly, does it? All it needs to know is the pixel resolution
A pixel when viewed on a computer monitor do not have a size because its just stored data but that data represents a sampling of a image at a 2 dimensional resolution that did occupy a space on the sensors surface.

08-24-2019, 01:23 AM - 1 Like   #230
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QuoteOriginally posted by Ian Stuart Forsyth Quote
Sure they doe have a physical size or I would not be able to photograph them
Here is the k7 Kind of look like they have a size too me
You are photographing a sensor. Re-read my quoted words. In an image file pixels do not have a physical size
08-24-2019, 01:24 AM   #231
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QuoteOriginally posted by Ian Stuart Forsyth Quote
Sure they doe have a physical size or I would not be able to photograph them
Here is the k7 Kind of look like they have a size too me
You are photographing a sensor. Re-read my quoted words. In an image file pixels do not have a physical size
08-24-2019, 01:24 AM - 2 Likes   #232
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QuoteOriginally posted by Photobill Quote
So what your saying is as the OP in my original question I just miss spoke (used the wrong term) when I used the term "EQUIVALENT EXPOSURE" I should of said "get the same exposure"? The term " EQUIVALENT EXPOSURE" refers to exposure (SS, ISO & F:stop) + FOV?

Don't let them con you into blaming yourself for the mess this thread ended up in. Most actual photographers would take the term "equivalent exposure" to mean the phenomenon of reciprocity. 1/125 at f/11 at ISO 100 is equivalent to 1/250 at f/8 at ISO 100, and they are both equivalent to 1/500 at f/11 at ISO 400. . . and so on. They are all the same amount of exposure.

But unfortunately there are equivalentists. People who have become obsessed with the idea of trying to take photos with the same field of view, same depth of field, and same amount of noise on two different formats. So they always assume that that's what the word equivalent means whenever it crops up.

Once they'd got it into their heads that they wanted to do this same photo on different formats thing, they started imagining how cameras would have to work to make it happen. What they ended up with doesn't have much resemblance to the way that digital cameras actually do work. . . but hey, as long as it makes equivalence seem to work then that's all that matters. And they'll now dive into any thread where anyone uses the word "equivalent" in any context, reciting the same litany of myths over and over again, hoping that eventually people who do know how cameras work will stop correcting them so that they can imagine they've won.

So to boil it all down: Equivalence is an attempt to explain how digital cameras work, but it only makes sense if you ignore how digital cameras actually work. Hope that clarifies things.
08-24-2019, 01:27 AM - 2 Likes   #233
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QuoteOriginally posted by Ian Stuart Forsyth Quote
The magnification is the size difference between the image projected onto the sensor and how you ether view the image on the screen or whether you print it. it all comes from that projected image which has a size. you zoom in with your computer screen you are zooming in more on that projected image.
Nope. When an image is recorded in digital form by each pixel in a sensor it has no size at all. View that image file at 100% on a computer screen or a soccer stadium large screen..... and each pixel will be displayed at a physical size based only on the resolution of the viewing medium.

08-24-2019, 01:37 AM - 3 Likes   #234
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QuoteOriginally posted by Ian Stuart Forsyth Quote

So when you use the term equivalent exposure most people take that as meaning total light. Equivalent exposure is one that uses the same shutter speed and entrance pupil for there equivalent lenses with the same FOV.


.
In the real world (not Humpty Dumpty in Wonderland) equivalent exposure is used to mean any combination of shutter speed, aperture and ISO that gives the same exposure.

eg 1/250 f8 ISO 100 is equivalent to
1/125 f11 ISO 100

https://www.shutterbug.com/content/equivalent-exposure


Edit. Dartmoor Dave beat me to it.
08-24-2019, 01:45 AM - 1 Like   #235
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QuoteOriginally posted by Ian Stuart Forsyth Quote
Sure they doe have a physical size or I would not be able to photograph themHere is the k7 Kind of look like they have a size too me

Cool, a photo of a K7 sensor. So let's talk about what we're actually seeing here.

Each of those tiny little square things is a pixel. Each pixel holds a photodiode that converts photons into electrons, plus various transistors that read the accumulated charge, reset the diode to take another photo, etc. . .

Once the accumulated charge has been measured, it's converted into a digital value and saved. It isn't saved as a physical instance of a thing of an actual size -- in the way that the grains of chemicals on a piece of film are -- it's just a number representing a measured value. It no longer has any physical size, and it will continue not to have any physical size until the number gets converted into some display medium that does have a physical size so that human beings can look at it.

The great thing about it being just numbers is that we can do all sorts of amazing things with the data on our computers, which we call post-processing. And speaking of computers, I notice that none of the equivalentists have explained yet how my computer enlarges the physical size of my sensor to the physical size of my screen, when it doesn't know what those sizes are.

Last edited by Dartmoor Dave; 08-24-2019 at 01:52 AM.
08-24-2019, 01:57 AM   #236
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QuoteOriginally posted by Photobill Quote
So what your saying is as the OP in my original question I just miss spoke (used the wrong term) when I used the term "EQUIVALENT EXPOSURE" I should of said "get the same exposure"?
The term " EQUIVALENT EXPOSURE" refers to exposure (SS, ISO & F:stop) + FOV?
The most common use of equivalent exposure that I have seen being used in photography is that of one that uses the same equivalent FOV, the same subject distance, the same shutter speed, the equivalent DOF ( this would be a different ƒstop) and equivalent iso ( this would a different iso).

In photography we are mostly interested in these 4 things FOV, DOF, Shutter speed and subject distance as these are how we use our cameras to captured images.

Shutter speed allows us to control how much light we let in and how much motion we capture.
ƒ stop also allows us to control how much light we let in and also how much of the image is acceptably sharp with DOV control
Subject distance really sets up the perspective of the image.
This is why the common use of trying to capture equivalent images we try and hold these options that we have at our disposal.
So if we want to compare how each format can work within this controls we look towards equivalency to tell us how the format size influences the setting used in the camera and to get these equivalent photographs.

If we want to capture equivalent DOF then we need to use different ƒstops, if we want to let the same amount of light thru the lens for each formats then we also need to use a different ƒstop. And by this time I hope that you can see that equivalent ƒstops will let the same amount of light and also have the same DOF as they are closely tied together.

If want to shoot with the same amount of motion blur then we need to use the same shutter speed.

If we want to shoot the same image with the same perspective then we need to shoot from the same position with the camera.

If we want to capture the same image with same FOV we also have to use a different FL to hold that FOV.

If we want to hold the same outgoing image lightness because we are using a different ƒstop for the same DOF we need to use a different iso setting.
08-24-2019, 02:03 AM - 1 Like   #237
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QuoteOriginally posted by Ian Stuart Forsyth Quote
The most common use of equivalent exposure that I have seen being used in photography is that of one that uses the same equivalent FOV, the same subject distance, the same shutter speed, the equivalent DOF ( this would be a different ƒstop) and equivalent iso ( this would a different iso).

No it isn't.


https://lmgtfy.com/?q=equivalent+exposure
08-24-2019, 02:03 AM - 1 Like   #238
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When I go out to take pictures with a K-1 I don't give two hoots what settings a K-3 would use to get a similar picture. I really don't.
08-24-2019, 02:04 AM - 1 Like   #239
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QuoteOriginally posted by Photobill Quote
The term " EQUIVALENT EXPOSURE" refers to exposure (SS, ISO & F:stop) + FOV?
Only to nutters.
It is a great example of Pavlova's dog syndrone -
Use the word "equivalent" and all the equivalencers start salivating!
08-24-2019, 02:21 AM   #240
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QuoteOriginally posted by Ian Stuart Forsyth Quote
Lets use a 200mm ƒ/2.8 for a cropped sensor and look at the size of the front element and then compare it to that of a lens that will project the same FOV on a FF body, you would need 300mm. Now if we look at a 300mm ƒ/2.8 that front element is much larger than the one found on that 200m ƒ2.8 lens. Larger front element = more light for the same exposure . As you can see for the same FOV and the same ƒ/2.8 there will be very different amounts of light going thru the lens and onto their sensors.
Once more you are showing total ignorance of the inverse square law. The 300mm iris is 50% further from the sensor. It needs to be physically 50% larger in diameter to give the same light intensity on the pixels.
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