A reminder for some memebers as to what the F stop is all about.

Started Jan 26, 2014 | Discussions
windsprite
windsprite Senior Member • Posts: 2,754
Re: After reading your " Sensors measure charge not current"
8

rhlpetrus wrote:

Bob, this is hopeless.

Don't give up so easily. The discussion has only been going on for ten years or so.

Julie

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windsprite
windsprite Senior Member • Posts: 2,754
Re: A reminder for some memebers as to what the F stop is all about.

bobn2 wrote:

windsprite wrote:

Messier Object wrote:

I don't often agree with Bob, however one needs to consider that the image made with the larger sensor and the 2x longer lens shows the same scene, but has been generated from 4x as many photons.

Why don't you often agree with Bob, then? The above, or some derivative of it, is basically all he ever says.

I don't know, sometimes I've been known to say 'who's buying the next round?'.

I stand corrected! And since it's just past Happy Hour here, I can truthfully say I'm still standing. Ba-dump-bump.

Julie

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Kim R Forum Pro • Posts: 17,895
Re: After reading your " Sensors measure charge not current"
4

windsprite wrote:

rhlpetrus wrote:

Bob, this is hopeless.

Don't give up so easily. The discussion has only been going on for ten years or so.

Julie

LOL  Love your sense of humor!

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bobn2
bobn2 Forum Pro • Posts: 64,317
Re: After reading your " Sensors measure charge not current"
5

rhlpetrus wrote:

bobn2 wrote:

gsergei wrote:

I am positive you have never finished your high school.

If you mean that I have never stopped learning, you are right.

Overall - a superb technical illiteracy. Can't argue with you, sorry.

I had realised that you can't argue with me, and yes you do display exactly the illiteracy you talk about.

BTW, the term "charge" is used for capacitance and is measured in Culons or Farades as in capacitors, not light sensitive diodes output , which is voltage/current.

'Coulombs' (for that is what it is) is the unit of charge. 'Farads' (for that is what they are) are the unit of capacitance. They are not the same thing, but related by the formula Q=CV - i.e. the charge is equal to the capacitance times the voltage. Maybe best to work those out before trying to explain how a sensor works.

Bob, this is hopeless.

Hi Renato, it depends which bit you think is 'hopeless'. Agreed, there is probably no hope of actually teaching gsergei anything. On the other hand, via the discussion, a few fewer people might end up thinking he's right.

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Bob

bobn2
bobn2 Forum Pro • Posts: 64,317
Re: A reminder for some memebers as to what the F stop is all about.

windsprite wrote:

bobn2 wrote:

windsprite wrote:

Messier Object wrote:

I don't often agree with Bob, however one needs to consider that the image made with the larger sensor and the 2x longer lens shows the same scene, but has been generated from 4x as many photons.

Why don't you often agree with Bob, then? The above, or some derivative of it, is basically all he ever says.

I don't know, sometimes I've been known to say 'who's buying the next round?'.

I stand corrected! And since it's just past Happy Hour here, I can truthfully say I'm still standing. Ba-dump-bump.

My memory of Japan is that beer is served in shot glasses, which means you can neck quite a few and still stand up.

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Bob

philosomatographer
philosomatographer Contributing Member • Posts: 539
*THIS* is what f/2.0 is all about...
5

...from this weekend, 35-100mm f/2.0 at f/2.0 (Olympus E-5).

Really, who the hell cares about all these equivalency arguments. There are such finer aspects of image quality and lens rendering that have a much greater impact on your photography. f/2.0 is more than sufficient for effective subject isolation even when the subject is enormous, and a couple of meters away.

Close Encounter

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RoelHendrickx
RoelHendrickx Forum Pro • Posts: 26,844
Glad that you had such big aperture
4

philosomatographer wrote:

...from this weekend, 35-100mm f/2.0 at f/2.0 (Olympus E-5).

Really, who the hell cares about all these equivalency arguments. There are such finer aspects of image quality and lens rendering that have a much greater impact on your photography. f/2.0 is more than sufficient for effective subject isolation even when the subject is enormous, and a couple of meters away.

Close Encounter

Glad that you had such big aperture.

Because the elephant would never have fitted in a smaller aperture.

No, seriously : that's an impressive shot.

Be glad that our 2x cropfactor allowed you to stay a bit further back.

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bobn2
bobn2 Forum Pro • Posts: 64,317
Re: After reading your " Sensors measure charge not current"
1

jnd wrote:

rhlpetrus wrote:

bobn2 wrote:

gsergei wrote:

I am positive you have never finished your high school.

If you mean that I have never stopped learning, you are right.

Overall - a superb technical illiteracy. Can't argue with you, sorry.

I had realised that you can't argue with me, and yes you do display exactly the illiteracy you talk about.

BTW, the term "charge" is used for capacitance and is measured in Culons or Farades as in capacitors, not light sensitive diodes output , which is voltage/current.

'Coulombs' (for that is what it is) is the unit of charge. 'Farads' (for that is what they are) are the unit of capacitance. They are not the same thing, but related by the formula Q=CV - i.e. the charge is equal to the capacitance times the voltage. Maybe best to work those out before trying to explain how a sensor works.

Bob, this is hopeless.

Hopeless for what, providing factually correct information? OP tried to post yet another thread which will make things straight, yet made couple mistakes, so those should be pointed out.

BTW do you know what CCD stands for? "A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value." (courtesy of Wikipedia).

I think Renato knows that. I think you've probably misunderstood what he was saying is 'hopeless'.

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Bob

Danielvr Veteran Member • Posts: 5,105
Trees and apples
1

We get that all the time with our teenage son.

We will remark on something about his behaviour or whatever; and he knows that we are right; but instead of just admitting it, he tries to find a mispronunciation in what we said.

Well, you of all people should appreciate that!
"You may be right materially, dad, but formally it just won't stand!"

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RoelHendrickx
RoelHendrickx Forum Pro • Posts: 26,844
Re: Trees and apples
1

Danielvr wrote:

We get that all the time with our teenage son.

We will remark on something about his behaviour or whatever; and he knows that we are right; but instead of just admitting it, he tries to find a mispronunciation in what we said.

Well, you of all people should appreciate that!
"You may be right materially, dad, but formally it just won't stand!"

Quite frequently all of us together are rolling over the floor laughing.

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philosomatographer
philosomatographer Contributing Member • Posts: 539
Re: Glad that you had such big aperture
1

RoelHendrickx wrote:

Glad that you had such big aperture.

Because the elephant would never have fitted in a smaller aperture.

No, seriously : that's an impressive shot.

Be glad that our 2x cropfactor allowed you to stay a bit further back.

Thanks, Roel!

My post was a little facetious I grant, luckily so was your reply (with "crop factor" and all...)

I certainly not only not feel limited by any equivalence argument, but I am liberated by the photographic opportunities I can take with the four thirds gear.

Sure, when I want very shallow depth of field with a normal view, I use my Summilux ASPH on my Leica rangefinder:

Cat and Lemon Trees

But when I want the ultimate in image quality and versatility insofar as lens performance is concerned, I reach for my E-5 and the SHG zooms.

Anybody still participating in the "equivalence" debate have a serious dead-horse-beating fetish - they should get out and take some photos, possibly with a "full-frame" system. Just remember to stop down those lenses to f/8 for a nice and even performance across the frame!

I use four thirds, 35mm "full-frame" (Leica), 6x7cm Medium Format (Mamiya), and 4x5in (Linhof) all on a regular basis. There are no optically better lenses than the Olympus SHGs when looking across all optical parameters.

Zeiss is the only manufacturer to have "caught on" with having to produce retrofocus, oversized lenses for ultimate performance on digital (the Otus 55/1.4). Manual focus, no weather sealing, single focal length, $3.5K

It'll be a while before somebody applies those ideas to an ultimate-performance f/4.0 (for "equivalence"), fast-focusing, fully weather-sealed zoom lens for 35mm sensors. Then we'll talk about cost and size, compared to the ZD 14-35mm f/2.0!

As it stands, we have junk like the Nikon 16-35mm f/4.0 that is not only huge like a telephoto lens, but distorts like a fisheye. See - only if they severely compromise on one parameter (distortion) do they manage a good showing with the others.

Truly uncompromising lenses are very rare in the 35mm world, yet we have them in the form of four zooms covering 7mm to 250mm in the four-thirds system. Of course, due to abandoned development, we are stuck with a "compromised" sensor, but such is life.

So - what were we debating in this thread again?

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bobn2
bobn2 Forum Pro • Posts: 64,317
Re: Glad that you had such big aperture
6

philosomatographer wrote:

Anybody still participating in the "equivalence" debate have a serious dead-horse-beating fetish - they should get out and take some photos, possibly with a "full-frame" system. Just remember to stop down those lenses to f/8 for a nice and even performance across the frame!

If someone were to perform their photography at f/8 all the time, then there is no point to having an FF system. I suspect that a lot of people who don't understand equivalence have wasted their money that way. You can get the same results using FT at f/4, and have a smaller, lighter, cheaper system. Then again, you could get the same results using a top-end 1/1.8" compact at f/2, and have an even smaller lighter system. I've got FF, APS-C, Four Thirds and 1/2.4" interchangeable lens cameras. So long as the DOF is in a range they can all do, they'll produce almost identical results (given there is about 1 stop variation between them in sensor efficiency). So, apart from the benefit of more pixels, my Pentax Q at f/2 produces very, very similar results to my D800 at f/11 and is very much smaller.

I use four thirds, 35mm "full-frame" (Leica), 6x7cm Medium Format (Mamiya), and 4x5in (Linhof) all on a regular basis. There are no optically better lenses than the Olympus SHGs when looking across all optical parameters.

That is disputable. Certainly, the Olympus SHGs are very, very good, but 'there are no better' is a very strong statement that I don't believe you can substantiate.

As it stands, we have junk like the Nikon 16-35mm f/4.0 that is not only huge like a telephoto lens, but distorts like a fisheye. See - only if they severely compromise on one parameter (distortion) do they manage a good showing with the others.

Calling it 'junk' is simply extreme. It is of course a compromise lens, in Nikon's equivalent of the HG, not SHG lens, and it is giving the equivalent of an 8-17.5 f/2 lens on four thirds. It's worthwhile noting that the much vaunted Olympus equivalent, the 7-14 is only an f/4 lens, equivalent to an f/8 on FF. If Nikon were to make a 14-28/8, no-one would buy it, because it would be a simply pointless lens on FF.

Truly uncompromising lenses are very rare in the 35mm world, yet we have them in the form of four zooms covering 7mm to 250mm in the four-thirds system.

Yet the four thirds lenses are indeed 'compromised' in terms of light gathering power with respect to FF lenses. But then, making such lenses for FF would be pointless because you'd get the worst of both worlds, lower light gathering and large size. In the end, equivalence isn't at all about whether FF or FT is 'better' or 'compromised' it's about knowing what the tradeoffs are (in both cases) and deciding for yourself.

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Bob

tko Forum Pro • Posts: 13,065
Re: A reminder for some members as to what the F stop is all about.
5

They say things like " convince me, that the amount of light going through Olympus 25/2.8 is the same compared to Canon, e.g., 50/1.4 set to 2.8". I have to disappoint you.

Let save this statement, because the facts are about to get twisted very soon. Notice that in this comparison, the focal length of the Canon has doubled, as it should (but later . . .)

also there is a lot of "expert talk" that bigger lenses allow more light and therefore this results in less noise in the image. This is total BS.

How can any sane person NOT think a bigger lens lets in less light? So, astronomers have no interest in bigger telescopes? Really, this discussion should stop right here with this statement.

Now let's go through some lesson of optics. Some people visiting this website have no knowledge about the school items like : candela (don't confuse with Nelson Mandela), lumen, brightness, decibel, voltage, Amper, semiconductor electronic noise level, relative to signal vs absolute, etc.

And some are optical experts, rocket scientists, electrical engineers, with years of training in doing this stuff. Which one are you?

So, F2 on a lens means that this diameter of the opening of the optical instrument can fit TWO times into its focal length. For a 50 mm F2 lens it means that the aperture diameter at F2 is 25 mm.

Ah, but now you've conveniently forgotten that the Canon needs twice the FL for the same FOV, as you correctly pointed out before. By your own (correct) math, the M43rd 25MM lens has an opening of 12.5MM and the equivalent 50MM Canon lens has an opening of 25MM. Oops, twice the diameter, four times the light. This isn't rocket science. For the same FOV, you have half the FL in M4rds, which is half the diameter and four times less light.

Simple. No degree necessary.

Now about the sensor noise on FF cameras vs. 4/3 vs anything else. The ONLY reason why they (FF) have less noise and better dynamic range is because their individual photosites are BIGGER electronic devices. Any semiconductor/ transistor/ diode has its electronic noise, because inside its P-N-P or N-P-N layers there are electrons which move randomly even when there is no "useful" signal. This chaotic movement is called "noise". A bigger semiconductor device can put through higher DC current and have "relatively" less noise.

It's funny when non-technical people try to (mis)describe well known analysis. The bulk of the noise is due to the quantum nature of light, and it's inherent randomness. Less light = more randomness = more noise. Actually, the number of errors in this one paragraph is staggering. Sensors aren't diodes, sensor don't carry current, and sensors have noise due to thermal contributions.

This is kind of like flat earth arguments, where a non-technical person hijacks a lot of technical information he doesn't understand, and twists it to his point of view.

tko Forum Pro • Posts: 13,065
simply embarrassing
7

No point in arguing with the true believers.

I am positive you have never finished your high school.

Overall - a superb technical illiteracy. Can't argue with you, sorry.

BTW, the term "charge" is used for capacitance and is measured in Culons or Farades as in capacitors, not light sensitive diodes output , which is voltage/current.

You don't have a clue. Charge is the number of stationary electronics. Current is the moving electrons. Sensors are capacitive devices, not diodes. Charge coupled devices = CCD (you've heard that term before?)

Next time spell Coulombs and Farads right, or use cut and paste from whatever web site you're visiting.

It will be amusing to see the resulting indignant technical mishmash and insults you'll retort with.

Lets see a show of hands. How many believe a larger telescope doesn't let in more light?

veroman Veteran Member • Posts: 4,862
Re: A reminder for some memebers as to what the F stop is all about.

gsergei wrote:

.... If Olympus were to put only 3 Mp into their 4/3 sensor it would be the same of better than any Canikon you know in terms of noise and DR, but then you would complain about the low resolution ....

Sergie: according to what you've posted, the E-1 ... with "only" 5MP and rather large photo sites ... should then have outperformed the competition in the noise and DR departments,  but it didn't and doesn't. How come?

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goblin
goblin Veteran Member • Posts: 3,544
Re: A reminder for some memebers as to what the F stop is all about.

veroman wrote:

Sergie: according to what you've posted, the E-1 ... with "only" 5MP and rather large photo sites ... should then have outperformed the competition in the noise and DR departments, but it didn't and doesn't. How come?

Oh, come on, that's a cheap one...
It is clear that the above is only true in an "all other things being equal" context, which implies sensors of sorta kinda the same generation. And same technology, which is why the whole photosite size story can be correct most of the time but by no means universal.

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Great Bustard Forum Pro • Posts: 44,114
Entirely incorrect.
4

gsergei wrote:

Hi, all.

I've just had a quick look at the thread started by Dave Gaines about equivalence , again. He has made a very good point overall. Surprisingly, there are still photographers who fundamentally don't know what the aperture is all about. They say things like " convince me, that the amount of light going through Olympus 25/2.8 is the same compared to Canon, e.g., 50/1.4 set to 2.8". I have to disappoint you: YES ,it is the same. Why? -because it is a relative measure, not absolute. F2.8 on a Lumix LX3 allows the same illumination of sensor as PL 25/1.4 set to F2.8, the same as Canon 50/1.4 set to F2.8 !!!

also there is a lot of "expert talk" that bigger lenses allow more light and therefore this results in less noise in the image. This is total BS.

Now let's go through some lesson of optics. Some people visiting this website have no knowledge about the school items like : candela (don't confuse with Nelson Mandela), lumen, brightness, decibel, voltage, Amper, semiconductor electronic noise level, relative to signal vs absolute, etc.

So, F2 on a lens means that this diameter of the opening of the optical instrument can fit TWO times into its focal length. For a 50 mm F2 lens it means that the aperture diameter at F2 is 25 mm. That's it, people. It has never meant FF versus 4/3 versus whatever sensor/film size you had in your camera. Just the optical geometry. Easy ? Accordingly , F11 means that this diaphragm /aperture diameter will fit 11 times into the instrument's focal length. It's been like that since the inception of photography in the 19th century.

Now about the sensor noise on FF cameras vs. 4/3 vs anything else. The ONLY reason why they (FF) have less noise and better dynamic range is because their individual photosites are BIGGER electronic devices. Any semiconductor/ transistor/ diode has its electronic noise, because inside its P-N-P or N-P-N layers there are electrons which move randomly even when there is no "useful" signal. This chaotic movement is called "noise". A bigger semiconductor device can put through higher DC current and have "relatively" less noise.

The DPR once had a very useful parameter in the camera specification table describing the sensor's photosite in micrometers. there one could easily see that larger Canikons had bigger photosites, something like 8 micrometers vs Olympus's (don't remember precisely) 4.6 or something like that, therefore their light sensitive "transistors" were bigger and could provide higher DC current compared to Olympus's or any other smaller sensor. It is This DC micro current that gives you higher DR and less noise, NOT the size of the sensor. Mind you , if Canon were to put 50 megapixel into its FF sensor it will have a much worse performance for noise and DR compared to their own 16 Mp or whatever on their current offerings. Again it has to do with pixel density (diodes per square mm) and size of the electronic device,it has nothing to do with 36x24 mm. If Olympus were to put only 3 Mp into their 4/3 sensor it would be the same of better than any Canikon you know in terms of noise and DR, but then you would complain about the low resolution, yeah, right !

The megapixel race is for stupid consumers and marketing boys/ploys, it has nothing to do with photography. I am totally against it. I don[t need even 16 MP on my EM1 and would love to see a new Olympus sensor with 10 or even 8 MP but with a higher quality sensor properties. That's it.

In the mean time : kudos to Olympus engineers for designing their fine lenses !

thank you for reading and now I will retire to my morning coffee.

Photo amen to all of you.

Wow. Just wow. Everything you wrote is entirely incorrect, and I will prove it wrong with a single example that you can all do at home.

Let's take a photo of a scene with an E5 + 35-100 / 2 at 50mm f/2 1/200 ISO 3200 and 100mm f/2 1/200 ISO 3200 (note that we have used the same lens, same f-ratio, same shutter speed, same ISO, same sensor, and thus same sensor efficiency and pixel size).

We now crop the 50mm photo to the same framing as the 100mm photo and display both photos at the same size. Which photo is more noisy and why?

(Hint: while the sensors are the same size, the cropped photo uses only 1/4 the area of the sensor, and thus only 1/4 as much light makes up the cropped photo as the uncropped photo.)

bobn2
bobn2 Forum Pro • Posts: 64,317
Re: A reminder for some memebers as to what the F stop is all about.
2

goblin wrote:

veroman wrote:

Sergie: according to what you've posted, the E-1 ... with "only" 5MP and rather large photo sites ... should then have outperformed the competition in the noise and DR departments, but it didn't and doesn't. How come?

Oh, come on, that's a cheap one...
It is clear that the above is only true in an "all other things being equal" context, which implies sensors of sorta kinda the same generation.

Compare it with cameras of the same generation....

And same technology, which is why the whole photosite size story can be correct most of the time but by no means universal.

No-one has put up any good evidence that the 'whole photosite size' story works at all, yet alone that it is 'correct most of the time'.

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Bob

(unknown member) Veteran Member • Posts: 9,549
Both sides are sort of right
3

As far as I can tell, the amount light is relative. Light does not increase in density  or anything like that with a full frame, and 2.8=2.8 as far as shutter speed and iso goes.

The main difference with sensor size is that the larger the  sensor, the less you have to enlarge the image when developing it. That's why full frame (and medium and large format) tend to have more resolution even with the same megapixels. It was the same in film days. Increased megapixels  is sort of like using a finer film grain, but it's only going to get you so far.

Depth of field differences we all know and can all agree on.

DR and noise differences depend as much on current tech as anything else, so we see a D7100 outscoring Canon full frame sensors on DXO. Clearly though,  we can see the there is both a correlation between sensor size and these things, and sensor tech and these things, at least at this point in digital camera development.

All that said, the differences between these cameras is not worth arguing about (though I admit it can be fun sometimes).

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John Krumm
Juneau, AK

veroman Veteran Member • Posts: 4,862
Re: A reminder for some memebers as to what the F stop is all about.

goblin wrote:

veroman wrote:

Sergie: according to what you've posted, the E-1 ... with "only" 5MP and rather large photo sites ... should then have outperformed the competition in the noise and DR departments, but it didn't and doesn't. How come?

Oh, come on, that's a cheap one...
It is clear that the above is only true in an "all other things being equal" context, which implies sensors of sorta kinda the same generation. And same technology, which is why the whole photosite size story can be correct most of the time but by no means universal.

I was speaking of "the same generation" when I said the E-1 should THEN have outperformed the competition. Again ... it didn't, still doesn't and never will. Again, according to what was posted, it should have. Seems someone or something is in error.

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