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10-09-2014, 07:24 AM   #31
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QuoteOriginally posted by JinDesu Quote
Or even just take a Nikon D800 and put it into crop mode. I assure you, putting the sensor into crop mode will not change your shutter speed/aperture/ISO given a specific exposure.
Northrup addreses this point specifically. The pricipal difference is in the noisiness of the image, reflecting the fact that in order to give an image of the same brightness from the fewer photons that are striking the smaller sensor, the camera is internally boosting its sensitivity.

10-09-2014, 07:29 AM   #32
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QuoteOriginally posted by Andi Lo Quote
I tested this myself, shooting 75mm/2.8 on FF yields a virtually identical image (DOF wise) to 50/2 on APSC. I'd assume the rest of the focal range is the same as well. Had both cameras side by side and I didnt change my distance (its a half body portrait). I dont think I bothered to make the ISO / shutterspeed the same, was only concerned with DOF when I did the tryout. I can post the images later if you want )
Why wouldn't it ? The contention here is that using the same lens on different formats somehow changes its apparent focal length and aperture.
10-09-2014, 07:30 AM   #33
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QuoteOriginally posted by marcusBMG Quote
Northrup addreses this point specifically. The pricipal difference is in the noisiness of the image, reflecting the fact that in order to give an image of the same brightness from the fewer photons that are striking the smaller sensor, the camera is internally boosting its sensitivity.
....no.... that's not how physics or the sensor works...

A cropped sensor will receive the same quantity of light per area as a larger sensor. The larger sensor will always have more photosites/pixels than the smaller one - so when you look at an equivalent FOV image between a larger and a smaller sensor, the larger sensor has better noise signal when SCALED to an equal pixel count.

I.e. 36MP D800 vs 16MP cropped mode - at 100% crop the noise is the same. You can literally see this in person if you have a D800. You can also see this is true by comparing 100% crops of a D800 to a D7000. The noise at the pixel level is the same in quantity and size. However, upon scaling to equal (whether you scale the 36MP down to 16MP or scale the 16MP up to 36MP), the signal to noise ratio favors the larger sensor.

A larger sensor does not absorb more light than a smaller sensor of the same technology. It just has more pixels/photosites. That's all.
10-09-2014, 07:31 AM   #34
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QuoteOriginally posted by kh1234567890 Quote
Why wouldn't it ? The contention here is that using the same lens on different formats somehow changes its apparent focal length and aperture.
I thought we were discussing DOF on different formats. My original point that you quoted was that a 18-50/2 zoom doesnt exist for APSC. So FF is the only format where I can shoot a zoom lens with that kind of DOF control.

If you agree that 75/2.8 on FF is equal to 50/2 on APSC dof wise, there's no contention between us


Last edited by Andi Lo; 10-09-2014 at 07:36 AM.
10-09-2014, 07:35 AM   #35
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QuoteOriginally posted by JinDesu Quote
A larger sensor does not absorb more light than a smaller sensor of the same technology. It just has more pixels/photosites.
My G1 and K-2 have the same number of photosites being both 12 MPx so the essential difference is in the size of the photosites. using the familiar bucket collecting raindrops analogy, smaller photosites collect fewer photons.

My point that you quoted was imprecise - sounds like Northrup is making more of a generalisation when in fact if you see his video he is careful and specific about what he is comparing with what (what "goalposts" he is moving) - sorry about that.

The general point that a smaller sensor is being struck by a smaller number of photons in simple relation to its area stands.

Last edited by marcusBMG; 10-09-2014 at 07:46 AM.
10-09-2014, 07:37 AM - 1 Like   #36
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QuoteOriginally posted by Andi Lo Quote
I thought we were discussing DOF on different formats with diffferent lenses. My original point that you quoted was that a 18-50/2 zoom doesnt exist for APSC. So FF is the only format where I can shoot a zoom lens with that kind of DOF control.

If you agree that 75/2.8 on FF is equal to 50/2 on APSC dof wise, there's no contention between us
As long as the circle of confusion stays the same
10-09-2014, 07:38 AM   #37
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Equivalence is primarily of use to those who believe that decisions regarding the purchase, use, and evaluation of photographic gear should be made on the basis of numerical specs, rather than the appreciation of actual images. Few people know what one stop of DOF means in terms of actual images (and the only way to know that is by looking at images --- many, many images --- and comparing and making evaluations based on personal aesthetic ideals). Equivalence is presented as a scientific formula (which it is within physics), but when applied to photography it becomes a tacit value judgment, implying a special importance to narrow DOF and low-light performance at the expense of all those factors which equivalence blithely ignores (such as microcontrast, color rendition, AF performance, bokeh, rendering, post-processing, etc.).

QuoteOriginally posted by marcusBMG Quote
Your 70-200 f2.8 equates to 105-300 f4.2!!!
Maybe in terms of physics. But are the lenses aesthetically equivalent? Because, like it or not, photography is an aesthetic discipline which involves people making non-scientific value judgments. It's the images, and how they affect our aesthetic sensibilities, that count, not scientific formulas. A 70-200 f2.8 lens may equate, in terms of a few narrow parameters of physics, to a 105-300 f4.2 lens; but that does not mean you're going to get identical images from each lens! The sharpness, microcontrast, rendering, bokeh, color rendition of each lens, as well as how the data recorded by the camera's sensor is interpreted, will have a palpable effect on the images produced by each lens; an effect, moreover, which equivalence simply ignores.
10-09-2014, 07:45 AM   #38
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QuoteOriginally posted by marcusBMG Quote
or bigger photosites - thats the comparison between my Lumix G1 and K-r both 12MPx. And bigger photosites absorb more photons.
Then make your statement clearer. You are saying, when normalized to the same MP count (whether by having larger photosites or having more pixels overall), a full frame sensor will outperform a cropped sensor in noise performance by more than one stop. That statement is generally true and can be seen in DXO ratings of sensors. But if I take a picture with a D800 at a given shutter speed/aperture/ISO and then I physically crop it afterwards - the exposure has not changed. So saying that the cropped sensor captures less light defies the definition of shutter speed/aperture/ISO.

The distinction may not necessarily be useful to everyone, but it is a specific distinction that should be understood to have better clarity in defining the different formats.

10-09-2014, 07:55 AM   #39
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QuoteOriginally posted by JinDesu Quote
The distinction may not necessarily be useful to everyone, but it is a specific distinction that should be understood to have better clarity in defining the different formats.
Right.

QuoteOriginally posted by JinDesu Quote
You are saying, when normalized to the same MP count (whether by having larger photosites or having more pixels overall), a full frame sensor will outperform a cropped sensor in noise performance by more than one stop. That statement is generally true and can be seen in DXO ratings of sensors
Well actually, not being a physicist or technician, merely (somewhat) scientifically literate, I am merely saying that I agree..

QuoteOriginally posted by JinDesu Quote
But if I take a picture with a D800 at a given shutter speed/aperture/ISO and then I physically crop it afterwards - the exposure has not changed.
I don't think this is the same thing.
10-09-2014, 07:59 AM - 3 Likes   #40
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So, if I'm gonna print a negative (the first sensor) from my Spotmatic and crop the enlarged image to a smaller size on the print (a second sensor) the original lens F-stop equivalent is gonna be . . . ummm? Oh, wait! What if I was usin' my half-frame Oly Pen-F?

And should I do this calculation before or after I compose in the VF and push the shutter button?

The rumored next gotta have feature for digital cameras is a special chip to do equivalence calculations for all possible formats, lenses and brand claims.

It's announcement is being delayed owing to arguments over the CPU speed and RAM needed for conversions to 8x10 view camera formats with glass plate negs and whether there's a need for an instant paper printout of the data or just a wireless/Bluetooth link to The Cloud with direct display in PF threads.
10-09-2014, 08:04 AM   #41
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QuoteOriginally posted by marcusBMG Quote

I don't think this is the same thing.
But that is exactly what a cropped sensor does. It physically cropped the image you received. Pacer above me makes good sensor with mentioning film.

I'm pretty sure that a D800 and a D7000 does not do anything fancy with their ISO calculations just because they have different sensor sizes. If they did, you would immediately notice a difference in the D800 crop mode vs the D7000 normal output.
10-09-2014, 08:07 AM   #42
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I'm with Northrup, pacerr, I blame the marketing departments and their hired minions, they have a vested interest in confusion and misunderstanding...
10-09-2014, 08:07 AM   #43
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QuoteOriginally posted by marcusBMG Quote
How can a smaller sensor catch the same amount of light as a larger sensor. it can't and it doesn't.
So if I grab a Nikon D800 and mount a full frame lens, then take two photos with the same settings, but one with whole sensor, and one with "crop mode" enabled, the second photo will suddenly be darker? No, it will be equally bright. Light per area will be the same, total area will be smaller (so total light recorded will be smaller), but the photo frame will be equally bright (same exposure) and the DoF will be the same. Only the crop will have a smaller field of view, due to cut off corners. There is a reason why Sunny 16 rule doesn't care about the size of your film

Last edited by Na Horuk; 10-09-2014 at 08:12 AM.
10-09-2014, 08:13 AM   #44
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QuoteOriginally posted by JinDesu Quote
But that is exactly what a cropped sensor does. It physically cropped the image you received.
And at the same time much of the light transmitted through the lens is discarded, no longer hitting the sensor. Thats the moment at which the analogy pacerr gives falls down, I think. Taking a print from a neg is a completely different photographic moment to the taking of the pic.

---------- Post added 9th Oct 2014 at 16:20 ----------

QuoteOriginally posted by Na Horuk Quote
So if I grab a Nikon D800 and mount a full frame lens, then take two photos with the same settings, but one with whole sensor, and one with "crop mode" enabled, the second photo will suddenly be darker? No, it will be equally bright. Light per area will be the same, total area will be smaller, but the photo frame will be equally bright (same exposure) and the DoF will be the same. Only the crop will have a smaller field of view, due to cut off corners.
Because, as I already said, the camera compensates internally for the fewer (total) photons that are being collected, in order to conform with the set ASA.

QuoteOriginally posted by Na Horuk Quote
There is a reason why Sunny 16 rule doesn't care about the size of your film.
But it does care about your aperture. If you sell yourself a false aperture as per my original post then there are consequences
Actually I think the reason you can say that about the sunny 16 rule is not because there is less light hitting the smaller formats, it is because thats the way the ASA is defined - to allow for consistency between formats.

Last edited by marcusBMG; 10-09-2014 at 08:24 AM.
10-09-2014, 08:27 AM   #45
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QuoteOriginally posted by marcusBMG Quote
And at the same time much of the light transmitted through the lens is discarded, no longer hitting the sensor. Thats the moment at which the analogy pacerr gives falls down, I think. Taking a print from a neg is a completely different photographic moment to the taking of the pic.

Because, as I already said, the camera compensates internally for the fewer (total) photons that are being collected, in order to conform with the set ASA.

But it does care about your aperture. If you sell yourself a false aperture as per my original post then there are consequences
Take his film analogy, take the film and cut the edges off to fit a APS film size. The brightness will not change, and neither did the exposure and all relevant settings.

With regards to the Sunny 16 rule - take a fully manual 35mm camera and a fully manual 110 camera and take the same ISO100 film and cut it to fit the 110 camera. Shoot F16 and 1/125s and you will see that both cameras have the same image brightness when process. They just have different FOV/how large you can print them - but the exposure stays the same. Now, if you take a lens that is somehow F16 (a pinhole lens) and you mount it on the 35mm camera and you also mount it on the 110 camera, by posts in this thread, the 110 camera should see F16 x (110 film's crop factor) for the exposure - which is not a correct statement.
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