[beholder3]

.

Please, please, please try to stop thinking in terms of optical enlargement. It's just numerical values recording the charge captured by individual photodiodes.

Never stop thinking about enlargement.

The enlargement determines most relevant attributes, like noise and sharpness and dynamic range and dof.

Regardless of pixelcount or photodiodes working.

In these matters film and digital all work the same, like it or not.

Smartphone sensors only underperform a K-5 because of the much higher enlargement and its effects.

[pschlute]

But here is the thing, it did matter when the image was created, which means it will matter when you print it.

mmmm...so your assertion is ..."it mattered when I pressed the shutter so it matters now"

---------- Post added 08-23-19 at 07:56 PM ----------

It is not the images we look at that decides the size, it is how the image was captured that do.

If you look at a large printed image, how do you know the size of the negative if you did not capture the image?

In many fields like science or automation it is very important to know the size of the captured image.

Que ?

[stevebrot]

As I said I should know this, but I do not 😞

Thanks to anyone that can set me straight. 🙌

How many times did you run out of popcorn?


Steve

[GUB]

(of equal quality, only bigger, same exposure)

Define equal -- same micro elf count or same micro elf size?

[Bob 256]

One more time. I think I addressed this topic earlier or in another thread.

Assuming you have perfect glass with 100% transmission - everything else has to do with f-stop and scene brightness - period (almost -see below). The sensor is just a flat surface and if you image a gray rectangle on it, the brightness of that image will be the same regardless of focal-length, the size of the sensor, or the distance to the actual rectangle (assuming there is no air to reduce light intensity). Changing the f-stop will change the rectangle's image brightness.

This principle fails if you have a "point source" - an object so small that it is no longer rectangular but more like a star (which remain the same size in even the most powerful telescopes). The sensor brightness of point objects is related to the square of aperture (area) and not f-stop directly. If you have a 500mm f4 lens and a 50mm f4 lens, stars or point objects will appear about 100 times brighter using the 500mm lens because its aperture is 100 times larger (area-wise) in order for it to have the same f-stop (f4). Hence it gathers more light and point objects are brighter with a larger aperture at a given f-stop.

Now you might think the same would apply to a rectangle - increasing the aperture as in the previous example will gather more light. That's true but since it is a rectangle and the image is 10 times larger with the 500mm lens, that gathered light is spread over a sensor area 10 times as large and that makes the sensor brightness the same for the larger rectangle image. Not so with a point object - size stays the same (a point more or less).

Increase or decrease the sensor size and nothing changes (except the size of the rectangle in the finished image - due to cropping).

The one other factor I pointed out in the other thread is that sensor pixel density can have an effect on sensor sensitivity which is not related to the OP's question. Changing sensor sensitivity does not change the brightness of the image on the sensor though it will change the apparent brightness of the object (like putting sunglasses on). This can confuse some people because when a different size sensor is compared, the pixel density may change but if the same ISO is maintained (correcting for sensor sensitivity differences), that gray rectangle should stay the same gray.

Now throw in some not-so-perfect glass and some atmospherics (smokey air) and you will see some brightness changes from those sources, however the above rules apply prior to that happening.

[Dartmoor Dave]

Never stop thinking about enlargement.

The enlargement determines most relevant attributes, like noise and sharpness and dynamic range and dof.

Regardless of pixelcount or photodiodes working.

In these matters film and digital all work the same, like it or not.

Smartphone sensors only underperform a K-5 because of the much higher enlargement and its effects.

Then you might be able to answer a conundrum for me. You see, I've got computers around the house running Windows 7, Windows 10 and Ubuntu Linux. They each have monitors of different screen sizes, although the resolutions are all the same. I've been searching and searching on each operating system, but I can't seem to find where I enter the physical screen sizes I'm using. It's obvious where to enter the resolution, but physical screen size. . . nope.

I can't find anywhere to enter the physical size of my camera sensor either.

So how on earth do those computers know how to enlarge my photos correctly from the physical size of the sensor to the physical size of the screen? I'm starting to wonder: Do you think it might possibly be that all that actually matters is the pixel resolution?

(Breaking my cardinal rule about not posting with some glasses of grape-based happy juice inside me. Hope I spelt everything right.)

[slartibartfast01]

Now you might think the same would apply to a rectangle - increasing the aperture as in the previous example will gather more light. That's true but since it is a rectangle and the image is 10 times larger with the 500mm lens, that gathered light is spread over a sensor area 10 times as large and that makes the sensor brightness the same for the larger rectangle image. Not so with a point object - size stays the same (a point more or less).

Yes but a rectangle could be considered to be a infinite number of point sources.

[dbs]

How many times did you run out of popcorn?


Steve

Hi Steve

Well I have run out of popcorn, I was about to ask Photobill if he had any left....on second thoughts getting drunk with Dave that;ll do

Dave

[GUB]

So how on earth do those computers know how to enlarge my photos correctly from the physical size of the sensor to the physical size of the screen? I'm starting to wonder: Do you think it might possibly be that all that actually matters is the pixel resolution?

The elves have tape measures?

[Fogel70]

Then you might be able to answer a conundrum for me. You see, I've got computers around the house running Windows 7, Windows 10 and Ubuntu Linux. They each have monitors of different screen sizes, although the resolutions are all the same. I've been searching and searching on each operating system, but I can't seem to find where I enter the physical screen sizes I'm using. It's obvious where to enter the resolution, but physical screen size. . . nope.

I can't find anywhere to enter the physical size of my camera sensor either.

You enter it at the same place where you told your film camera to capture 36x24mm frames on the film.
It is called the shutter button.

So how on earth do those computers know how to enlarge my photos correctly from the physical size of the sensor to the physical size of the screen? I'm starting to wonder: Do you think it might possibly be that all that actually matters is the pixel resolution?


(Breaking my cardinal rule about not posting with some glasses of grape-based happy juice inside me. Hope I spelt everything right.)

[GUB]

You enter it at the same place where you told your film camera to capture 36x24mm frames on the film.
It is called the shutter button.

So on that basis sensor size is in the exif. You were asked where in the exif in post 204. Now is a good time to tell us.

[Gimbal]

Define equal -- same micro elf count or same micro elf size?

Same Tech level, but to make it easier let's say a K1 in crop mode and a K1 in full frame mode. Enlarge both images 20 times and the center crop rectangle will be identical.

[swanlefitte]

Just for fun was a song on a 78rpm longer than the song on a 45rmp record? Now days how long is that mp3 file?
A koen for the day.

[Photobill]

How many times did you run out of popcorn?


Steve

Just a couple of times Steve, I decided to move onto beer & pretzel's 😉

---------- Post added 08-23-19 at 11:12 PM ----------

Hi Steve

Well I have run out of popcorn, I was about to ask Photobill if he had any left....on second thoughts getting drunk with Dave that;ll do

Dave

Just made a big order from Amazon for pretzel's you need me to send some over Dave?



What have I learned today??
#01: Gub thinks the truck is more useful

#02: Dartmore Dave Really can blow my mind (great printer / megapixel factoid)

#03: Dartmore Dave might be on mushrooms, he's seeing fast moving elves painting.

#04: Gub might of got into Dartmore's Daves stash, he's seeing elves with tap measures.

#05: Make sure you stock up on snacks & beverages before you ask a question 😉

I don't know about that but i know the truck is more useful.

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.

microscopic elves painting oil paintings very quickly?

The elves have tape measures?

[Ian Stuart Forsyth]

My reply was to your post

But a meter only gives one reading.

One of the problems with this line of thinking is that for raw or jpg you can have vastly different size of exposures when deciding what is correctly exposed for that scene and the file formats jpg or raw when you are writing them to your card.

Yes the meter will only give you one reading but for raw or jpg they can be very different in the size when you select for those raw or jpg file if your goal is a correctly exposed image.

You are confusing the issue. My point is that a aps-c camera meter, a FF meter, a MF camera meter, and a handheld incident meter will all give the same exposure reading and all expose a scene identically. Yet you continue to claim that exposure is dependent on sensor size.

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.

---------- Post added 08-23-2019 at 11:42 PM ----------

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. "
Please answer it. And note the word exposure - not the term gathered light.

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.

---------- Post added 08-23-2019 at 11:49 PM ----------

Many, many moons ago when I would develop and print my own film, I would uses various sizes of paper, 5x4 or 10x8. I don't recall having to give a longer timed exposure on the 10x8 prints

If you are using the same speed of film and you are shooting at a shallower DOF then yes you can shoot your camera at the same shutter speed but once you need to shoot at the same DOF then yes you would need to shoot at a longer shutter speed.
For the larger format you need to stop the lens down for the same DOF and if you are holding your film speed you would need to slow down your shutter.

---------- Post added 08-24-2019 at 12:18 AM ----------

Does not a lens have a maximum opening? This opening would only allow in a maximum amount of light. Yes deferent sizes of sensor's can absorbs deferent amounts of light from the same lens but the exact same amount of light passes through the aperture???

Yes but as you just stated one will collect more light. of that light.

The one item that I have not seen brought up is:
Is it a lens designed for a aps-c or is it a lens designed for a FF?
The FF lens would allow in "MORE" light than a lens designed for a aps-c sensor so wouldn't it technically have better light gathering capability. ����������������������������
NO NEED TO ANSWER! I WAS JUST AMAZED IT NEVER GOT BROUGHT UP

You have to remember that different formats when using the same FL of lens on both cameras have very different FOV, what the small format is doing is disregarding some of the light and this narrows your FOV. So you will need to use a lens with a different FL to match the FOV for that other format .

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.

So the real light gathering ability of the larger format is that it can use a longer FL to project more light onto the sensor at ƒ/2.8 than a shorter FL lens ( same FOV) at the same ƒ/2.8 on a cropped body as it has a much smaller entrance pupil when compared to its FF counter part lens. 71mm entrance pupil for the cropped and for the FF lens 107mm entrance pupil.