Chris@sabor
Senior Member
Yes, so doesn't that prove that if you shoot the full frame will produce a better image if it can match the lower ISO in the dx?
Help me understand FX vs. DX
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Chris@sabor
Senior Member
Yes, I think that's exactly my point. He had to degrade the fx image to match the images of dx or micro 4/3s by the crop factor, if I'm understanding it correctly?
Take any lens and point her with the end towards a wall. Then shine a flashlight at the front element.
You'll see her cast the light at the wall. Now draw a square inside the circle of light.
If you divide that square into two parts, does that in any way affect the light hitting the now smaller part?
You'll see her cast the light at the wall. Now draw a square inside the circle of light.
If you divide that square into two parts, does that in any way affect the light hitting the now smaller part?
No. FX usually does better in low light because the sensor is physically larger, so the pixels themselves are physically larger. This means the larger pixel 'collect' more photons per pixel compared to a DX pixel.
I use a D7200 and D810 for birding. I could easily live without the D7200, its really a luxury tbh. I couldn't say that about the D810. The D7200 is not great for northern European winter birding, the D810 is. Even in summer the D810 cropped image is very very close to the D7200
Chris@sabor
Senior Member
Thank you all.
No. Tony's whole point in making that video is to get the same depth of field for a given image size with different sensor sizes. There is no "degrading" of the image, just cropping to match subject size and show depth of field. I like Tony's books and instruction, but I think he gets way to zealous about the f/stop crop factor thing he espouses.
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Chris@sabor
Senior Member
You're right, it was about DOF. Thank you for setting me straight!
It's confusing, but with all of your great posts I think I understand a little better...
Stoshowicz
Senior Member
Clarkvision: Does Pixel Size Matter
Excerpt
Conclusions
Current good quality sensors in digital cameras are photon noise limited. This means there is no possible improvement in performance for the high signal region (bright things in an image) except to increase quantum efficiency of the devices and/or the fractional active area for which the sensor converts photons to electrons (called the fill factor). As both of these properties are reasonably high already, there is limited room for improvement. And even if these properties were improved, there would still be a big difference between large and small pixels. Larger pixels enable higher signal-to-noise ratios at all levels, but especially at low signal levels, assuming the lens scales with the sensor. The obvious improvement still possible would be to reduce the read noise, but that would likely improve large sensors also, thus large sensors with large pixels will always have an advantage for the same field of view, and correspondingly longer focal length lenses are used. Whether the difference in noise is great enough for you to choose a larger sensor, and thus likely a larger and heavier camera, is a decision you must make for yourself.
When choosing between cameras with the same sized sensor but differing pixel counts, the one with larger pixels (and fewer total pixels) will have better high ISO and low light performance (assuming read noise and fixed pattern noise are similar, which may not be the case), while the camera with more pixels can deliver images with finer detail in good light. You will need to decide where that trade point is. My models show the optimum in DSLR-sized sensors have pixels around 5 microns. You will need to determine what your prime imaging will be. For low light work, I might bias the pixels to a little larger than 5 microns; if low light/high ISO work is not as important, I might bias my choice to slightly smaller than 5 microns. For P&S cameras with small sensors, I prefer cameras with pixels larger than 2 microns.
Because good digital cameras are photon noise limited, the larger pixels will always have higher signal-to-noise ratios unless someone finds a way around the laws of physics, which is highly unlikely. Important to remember, however, is larger pixels enable more light to be collected, but it is the lens that delivers the light. An analogy is buckets of water. A large bucket will hold more water than a small bucket. But if you want to collect more water in a given time, one must turn the faucet on higher. So too with cameras and lenses: the bigger lens collects more light and delivers it to the sensor.
Image detail can be blurred by diffraction. Diffraction is more of an issue with smaller pixels, so again cameras with larger pixels will perform better, giving sharper images with higher contrast in the fine details. A direct example of this effect is a small sensor P&S camera can be diffraction limitied at f/5.6 to f/8, whereas the larger pixels in a DSLR will not show the same effects until f/11, f/16, and slower. And given the same pixel count in the P&S and DSLR, the DSLR will resolve finer details.
My boiling down..
So to get similar noise AND detail results, one uses a longer lens on the FX and a lower ISO on the DX assuming the same number of pixels.
Excerpt
Conclusions
Current good quality sensors in digital cameras are photon noise limited. This means there is no possible improvement in performance for the high signal region (bright things in an image) except to increase quantum efficiency of the devices and/or the fractional active area for which the sensor converts photons to electrons (called the fill factor). As both of these properties are reasonably high already, there is limited room for improvement. And even if these properties were improved, there would still be a big difference between large and small pixels. Larger pixels enable higher signal-to-noise ratios at all levels, but especially at low signal levels, assuming the lens scales with the sensor. The obvious improvement still possible would be to reduce the read noise, but that would likely improve large sensors also, thus large sensors with large pixels will always have an advantage for the same field of view, and correspondingly longer focal length lenses are used. Whether the difference in noise is great enough for you to choose a larger sensor, and thus likely a larger and heavier camera, is a decision you must make for yourself.
When choosing between cameras with the same sized sensor but differing pixel counts, the one with larger pixels (and fewer total pixels) will have better high ISO and low light performance (assuming read noise and fixed pattern noise are similar, which may not be the case), while the camera with more pixels can deliver images with finer detail in good light. You will need to decide where that trade point is. My models show the optimum in DSLR-sized sensors have pixels around 5 microns. You will need to determine what your prime imaging will be. For low light work, I might bias the pixels to a little larger than 5 microns; if low light/high ISO work is not as important, I might bias my choice to slightly smaller than 5 microns. For P&S cameras with small sensors, I prefer cameras with pixels larger than 2 microns.
Because good digital cameras are photon noise limited, the larger pixels will always have higher signal-to-noise ratios unless someone finds a way around the laws of physics, which is highly unlikely. Important to remember, however, is larger pixels enable more light to be collected, but it is the lens that delivers the light. An analogy is buckets of water. A large bucket will hold more water than a small bucket. But if you want to collect more water in a given time, one must turn the faucet on higher. So too with cameras and lenses: the bigger lens collects more light and delivers it to the sensor.
Image detail can be blurred by diffraction. Diffraction is more of an issue with smaller pixels, so again cameras with larger pixels will perform better, giving sharper images with higher contrast in the fine details. A direct example of this effect is a small sensor P&S camera can be diffraction limitied at f/5.6 to f/8, whereas the larger pixels in a DSLR will not show the same effects until f/11, f/16, and slower. And given the same pixel count in the P&S and DSLR, the DSLR will resolve finer details.
My boiling down..
So to get similar noise AND detail results, one uses a longer lens on the FX and a lower ISO on the DX assuming the same number of pixels.
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Don Kuykendall_RIP
RIP :(
I have the D7100 and the D750. My longest lens is the 70-300. I will try to remember to shoot the D7100 at 300mm and then put the lens on the D750 and shoot at 300mm. then go home and crop the D750's image to the same view as I got on the D7100.
Did I get that correct?
Just for fun, not very scientific, and not the best subject, but i did a similar quick 'experiment' with crop factors earlier this year. Taken with a D810 and then a D7200. (Exif may show the D7200 photo as a D810, it wasnt. Software recognition error. Full exif shows last photo as 700mm equivalent)
D810 Uncropped
D810 Cropped
D7200
D810 Uncropped
D810 Cropped
D7200
Chris as you saw it is a very valid question.
FX (general larger sensor):
- Generally larger pixels for same MP count (D750)
- Possible more pixels (D810) which allow to have more detail when resolution is reduced or allow to crop.
- uses more light (uses more of the circle of an FX lens)
- captures more light, but you need to be closer to your subject
DX (generally smaller sensor):
- Generally smaller pixels (more noise), but more pixels on the subject
- uses less light (uses less of the circle of an FX lens)
- captures less light, but you get the same field of view farther away from your subject
Larger pixels are good for quality (generally high ISO and colour depth per pixel). e.g. D4S, Sony A7S, Canon 1DX, ...
More pixels are good for resolution (more detail). e.g. D810, Sony A7RII, Canon 5DS R, ... but most go here to Medium Format (A lot of large pixels) Pentax 645, Hasselblad or Phase One
Example here are the high end cameras, since they are created as options for the professional users and proof that even they need to choose.
DX might waste light (uses less of the circle of FX lenses), but allows for smaller solutions (DX lenses) + impression of more reach (narrower field of view). The size of pixels like on a DX 24MP is currently not offered by Nikon on FX, so when you crop an FX to DX size you always loose megapixels (= detail) with the same lens and distance.
As others have concluded it depends on your situation between the D750 (better in dim light) and D7200 (better detail) and the difference is not huge, even if I believe it is important in practice, as most say having both is ideal. The D810 is a good intermediate between them. The other point is that the best Medium Format is unusable due to size and cost and availability.
That is why there is not one clear answer: you need to balance practical use, budget and importance of quality vs detail. Quality versus detail is where you seem to be in doubt still, like most involved in the discussion.
I think you understood something, FX captures more light for the same image (that means you need to be closer to the subject though), but you mix that up with there is a need a different aperture for the have the same exposure, which is wrong.
Exposure is only dependent on aperture and shutter speed, try to remember that.
On the other hand this does not help at all. I find the aperture crop factor as promoted by photozone for Depth of field equivalence, also not very helpful.
FX (general larger sensor):
- Generally larger pixels for same MP count (D750)
- Possible more pixels (D810) which allow to have more detail when resolution is reduced or allow to crop.
- uses more light (uses more of the circle of an FX lens)
- captures more light, but you need to be closer to your subject
DX (generally smaller sensor):
- Generally smaller pixels (more noise), but more pixels on the subject
- uses less light (uses less of the circle of an FX lens)
- captures less light, but you get the same field of view farther away from your subject
Larger pixels are good for quality (generally high ISO and colour depth per pixel). e.g. D4S, Sony A7S, Canon 1DX, ...
More pixels are good for resolution (more detail). e.g. D810, Sony A7RII, Canon 5DS R, ... but most go here to Medium Format (A lot of large pixels) Pentax 645, Hasselblad or Phase One
Example here are the high end cameras, since they are created as options for the professional users and proof that even they need to choose.
DX might waste light (uses less of the circle of FX lenses), but allows for smaller solutions (DX lenses) + impression of more reach (narrower field of view). The size of pixels like on a DX 24MP is currently not offered by Nikon on FX, so when you crop an FX to DX size you always loose megapixels (= detail) with the same lens and distance.
As others have concluded it depends on your situation between the D750 (better in dim light) and D7200 (better detail) and the difference is not huge, even if I believe it is important in practice, as most say having both is ideal. The D810 is a good intermediate between them. The other point is that the best Medium Format is unusable due to size and cost and availability.
That is why there is not one clear answer: you need to balance practical use, budget and importance of quality vs detail. Quality versus detail is where you seem to be in doubt still, like most involved in the discussion.
I think you understood something, FX captures more light for the same image (that means you need to be closer to the subject though), but you mix that up with there is a need a different aperture for the have the same exposure, which is wrong.
Exposure is only dependent on aperture and shutter speed, try to remember that.
On the other hand this does not help at all. I find the aperture crop factor as promoted by photozone for Depth of field equivalence, also not very helpful.
Danno
Senior Member
I always thought that the light was a constant... FX vs DX was an issue of geometry. Smaller smaller sensor changes the angles of the captured light coming thru the lens and that's it. It is like a pair of scissors. As you close them at the handle the angle of the tips get closer together too. The lens is allowing the same image thru, but the receptor at the end is smaller so instead of capturing an Image X size that you would with an FX you capture one X/1.5 or about 67% of the area. Since focal length affects the view-able angle an FX camera will capture what one would expect from a 35 mm camera from days past and the crop would only capture about 67% of the same image with the same lens...
Translating that to focal length a 100 mm lens on a DX camera captures the same size image as a 150 mm lens would capture on a FX.
Of course the ability to manage that that image is hindered in the DX because stuff is smaller, and you do not get the additional magnification of the FX lens, so they do seem to have less noise at higher ISO. I am sure there is additional clarity in the lens when it is tuned for FX or DX like zeroing a rifle scope at a given distance.
Translating that to focal length a 100 mm lens on a DX camera captures the same size image as a 150 mm lens would capture on a FX.
Of course the ability to manage that that image is hindered in the DX because stuff is smaller, and you do not get the additional magnification of the FX lens, so they do seem to have less noise at higher ISO. I am sure there is additional clarity in the lens when it is tuned for FX or DX like zeroing a rifle scope at a given distance.
Danno
Senior Member
I liked this video by Nikon.
FX & DX Format Lenses Explained | Learn About FX Lenses & DX Cameras from Nikon
FX & DX Format Lenses Explained | Learn About FX Lenses & DX Cameras from Nikon
Danno
Senior Member
You right, the lens shows what can be captured, but the sensor limits how much is able to be captured. I should have said angle of view captured on the sensor. I am taking this from those "angle of view" charts that are available to define the impact focal length has on angle of view.
thanks
Chris@sabor
Senior Member
I'm not trying to add to your work load but I would be very interested in your opinion based on first hand experience.
Thanks again Don!
Chris@sabor
Senior Member
On my monitor, I think the cropped D810 image appears better. I see less noise in the backround (look at the side mirror). This is with a higher megapixel than the D750 so still interested in seeing how that would fair,
Thank you for sharing this!
salukfan111
Senior Member
You are absolutely wrong. What comes out of the ass of a lens is the same regardless of what the lens is connected to. The sensor contains numerous targets and each target gets the same light intensity regardless of the size of the sensor. The new 50mp + sensors on the canons (and soon to be nikons) is nothing but an oversized dx sensor.