December 19, 2014, 08:55:54 PM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - AlanF

Pages: 1 ... 10 11 [12] 13 14 ... 79
166
Photography Technique / Re: Questions about Shooting the Supermoon
« on: August 13, 2014, 06:38:11 AM »
Nice shots, Alan and Febs.

For everyone who likes to photograph the moon, you should really try on the non-full phases. There is SO much more detail when the moon is a large crescent, half, and gibbous. The closer it gets to full, the less relief there is to show off all the surface detail. The best times, really, are a few days before through a few days after half, as you get the greatest amount of relief during that period, and the moon is bright enough not to require long exposures (crescents can be challenging, as you often need to use longer exposures....and it's best to use the lowest ISO you can get away with, as DR is still immense.)

Just used my time machine and picked up the 300/2.8+2xTC en route.

167
PowerShot / Re: SX 50 example
« on: August 12, 2014, 08:54:41 PM »
You want more. Well, here is a rainbow lorikeet at 1200mm, a well-known American at 674mm (I was able to sneak in a small camera into the audience) and sunset over Rome at 24mm.

168
Photography Technique / Re: Questions about Shooting the Supermoon
« on: August 11, 2014, 09:57:19 PM »
Am in Halifax, Nova Scotia, with just the Tamron 150-600 + 5DIII. It was somewhat cloudy, but I got a succession of shots, handheld at 1/1250, iso 640, f/8 600mm. Here is a typical one.Would have done better with the 300/2.8+2xTC on the 70D or 5DIII.

169
PowerShot / Re: SX 50 example
« on: August 11, 2014, 09:46:29 PM »
Alan, what settings did you use to be able to use Raw at 1200mm? I thought it was only jpeg. Thx

Program(me) or AV.

170
PowerShot / Re: SX 50 example
« on: August 11, 2014, 08:17:46 PM »
I have used the SX50 a lor for good bird photos. My favourite shot though is one of the Parthenon from the top of an apartment block in Athens, 2.2 km away. It was a typical hot evening with heat haze shimmer and and the Athens smog. 1200mm effective f, 1/320s, iso 80, hand held. Raw processed in DxO plus corrections for haze etc in PS. Downsized to 1200 px wide from 4000.

171
It must be a specific glitch with your lens, so send it back. I always use the central point focus and have taken several thousand shots with the Tamron on the 5DIII and have never encountered the problem you have found.

172
I actually had at one stage a 5dIII, 70D and 7D (with 300mm f/2.8II+2xTCIII) and tested them in good light by photographing lapwings on a raft at extreme distance. All the following shots are 100% crops, processed identically in DxO and with PRIME noise reduction, that virtually eliminates noise. Top is the 70D, which is 671x711 pixels; middle 7D; middle 7D, which is 643x655 pixels; bottom is 5DII, which is 483x447 pixels. In the next post, the 70D is tested against the 5DIII. Under these reach limited conditions, there seems little, if any advantage of using the APS-C.

Just off a cursory glance, it looks like the 5D III is better lit. If you don't mind, I'm going to downsample the middle 7D bird to the same size as the 5D III bird, so we can compare properly normalized results.
Please do so - I posted them to be used.

173
Really pushing it to catch a bittern a couple of 100 yards away. Again 100% crops, where the bird is just a few hundred pixels. The 70D is at the top. 5DIII at the bottom. There is no dramatic difference added by the extra reach. I am happy equally using either the 5DIII or the 70D in good light. However, the 5DIII is more tolerant to poorer light and is more resistant to camera shake for my hand held shots at lower shutter speeds.

174
I actually had at one stage a 5dIII, 70D and 7D (with 300mm f/2.8II+2xTCIII) and tested them in good light by photographing lapwings on a raft at extreme distance. All the following shots are 100% crops, processed identically in DxO and with PRIME noise reduction, that virtually eliminates noise. Top is the 70D, which is 671x711 pixels; middle 7D; middle 7D, which is 643x655 pixels; bottom is 5DII, which is 483x447 pixels. In the next post, the 70D is tested against the 5DIII. Under these reach limited conditions, there seems little, if any advantage of using the APS-C.

175
+1 My biggest mistakes are when my camera is set for point exposure for birds against a normal background and one flies by against the sky and I don't have time to dial in +2 ev to compensate or vice versa. Two more stops of DR would solve those problems.

This is a case where you want more DR to eliminate the need for the photographer to make the necessary exposure change. If you encounter this situation a lot, I highly recommend reading Art Morris' blog, and maybe buy his book "The Art of Bird Photography". He has an amazing technique for setting exposure quickly and accurately, such that making the necessary change quickly to handle this situation properly would not be a major issue.

Personally, I wouldn't consider this a situation where more DR is necessary. It might be a situation where more DR solves a problem presented by a lack of certain skills...but it is not actually a situation where more DR is really necessary.

Autofocus is not necessary, automatic metering is not necessary, IS is not necessary. The fact is that having those features makes it a lot easier, and having an extra couple of stops of DR would also make it easier. It is not a question of lack of skill but having a camera that eliminates one more variable.

176
Jrista,
Great images and informative discussion. I have learned a lot. Very confusing to noobs. I remember someone on CR frequently talking about better resolution being related to " number of pixels on target." So with reach limited subjects, you need either higher focal length lens or more (ie smaller) pixels per area on the sensor, to get better detail resolution. Did I say that correctly?

Yeah, that's correct. BTW, it's me who has always said "pixels on target". ;) I read that a long time ago on BPN forums, from Roger Clark I think, and started experimenting with it. I think it's the best way to describe the problem...because it scales. It doesn't matter how big the pixels are, or how big the sensor is...more pixels on target, the better the IQ. If you are only filling 10% of the frame, try to fill 50%. It doesn't matter if the frame is APS-C, FF, or something else...it's all relative.

It is not true as a general statement that the more pixels on target, the better. There have to be optimum sizes of pixels and optimal numbers on target, as shown by the following arguments. The signal to noise of a pixel increases with its area: the bigger the pixel, the greater the number of photons flowing through it and the greater the current generated, and the statistical variation in both becomes less important.

True. However that does not falsify my claims about pixels on target. We don't look at pixels. We look at images. Noise is relative to area. If you take 6.25µm pixels and 4.3µm pixels, you can fit 2.1 of the smaller pixels into every one of the larger pixels. Assuming the same technology (which is not actually the case with the 5D III and 7D...but humor me here), those 2.1 smaller pixels have the same amount of signal, and therefor the same amount of noise, as the single larger pixel. Noise is relative to area. If you increase the area of the sensor which your subject occupies, you reduce noise as a RELATIVE FACTOR.


The dynamic range is also greater for large pixels than can accommodate a large number of electrons. A low megapixel sensor should have very good signal to noise and DR, but poor resolution. Now, see what happens as we progress to the other extreme. As, we decrease the size of the pixel, the resolution increases but the statistical noise starts to increase as the number of photons hitting each pixel decreases per unit time.

Per-pixel noise is an absolute factor. You are absolutely right that larger pixels have less noise and higher dynamic range. However ultimately, to maximize IQ, you don't want to achieve some arbitrary balance between pixel size and pixel count. You simply want to maximize the number of pixels on subject, regardless of their size. Because it really isn't about the pixels...it's about the area of the sensor your subject occupies.

In a reach-limited situation, the absolute area of the sensor occupied by your subject is fixed...it doesn't matter how large the sensor is. You will be gathering the same amount of light in total for your subject regardless of what sensor your using, or how big it's pixels are. Therefor, the only other critical factor to IQ is detail...smaller pixels are better, in that case, all else being equal.

The electrical noise also increases until the inherent noise in the circuit becomes greater than that due to the fluctuation in number of electrons generated by the photons. We all experience this as the noise caused by increasing the iso setting. The dynamic range also decreases. Eventually, the pixel becomes so small that it loses all of its dynamic range because the well is so shallow it can hold only a few electrons.

Actually, electronic noise within the pixels themselves, ignoring all other sources of read noise (which tend to be downstream from the pixels) is due to dark current. Dark current noise is relative to pixel area and temperature...and dark current noise DROPS as pixel size drops. The amount of dark current that can flow through a photodiode is relative to it's area, just like the charge capacity of a photodiode is relative to it's area. So, technically speaking, electronic noise does not increase as pixel size decreases. Again, dark current noise is relative to the unit area...pixel size, ultimately, does not matter.

When it comes to read noise overall, that actually has far less to do with pixel size, and far more to do with the downstream pixel processing logic, how it's implemented, the frequency at which those circuits operate, etc. Most read noise comes from the ADC unit, especially when they are high frequency. I've seen read noise in CCD cameras that use Kodak KAF sensors change from one iteration to the next. A camera using a KAF-8000 series had as much as 40e- read noise a number of years ago. The same cameras today have ~7e- read noise. They are identical sensors...the only real difference is read noise. That's because read noise isn't a trait inherent to the sensor...it's related to all the logic that reads the sensor out and converts the analog signal to a digital signal. Canon could greatly reduce their read noise, without changing their sensor technology at all...because the majority of their noise comes from circuitry off-die in the DIGIC chips.

So, too large a pixel gives too little resolution, too small a pixel gives too much noise and too small dynamic range. You could have a 20 billion too small useless pixels on target where 20 million would be the optimal number. Because of the above reasoning, astrophotographers and astronomers match pixel size to their telescopes. For photographers, the optimal size for current sensors pixels is around the range of crop to FF.

Your ignoring the fact that you can always downsample an image made with a higher resolution sensor to the same smaller dimensions as an image made with bigger pixels. The 7D and 5D III are the cameras I used because they are the cameras I have. I often use the term "all else being equal" in my posts, because it's a critical factor. The 7D and 5D III are NOT "all else being equal". They are a generation apart. The 7D pixels are technologically inferior to the 5D III pixels.

So, ASSUMING ALL ELSE BEING EQUAL, there is absolutely no reason to pick larger pixels over smaller pixels, assuming your going to be framing your subject the same with identical sensor sizes. If your photographing a baboon's face, and you frame it so that face fills the frame with a nice amount of negative space. If you have a 10mp and 40mp camera, You should ALWAYS pick the sensor with smaller pixels. You can always downsample the 40mp image by a factor of two, and you'll have the same amount of noise as the 10mp camera. Noise is relative to unit area. It doesn't matter if that unit area is one pixel in a 10mp camera, or four pixels in a 40mp camera...it's still the same unit area. Average those four smaller pixels together, and you reduce noise by a factor of two. Which is exactly the same thing as binning for pixels during readout, which is also exactly the same thing as simply using a bigger pixel.

The caveat, here, is that with a 40mp sensor, you have the option of resolving more detail. You plain and simply don't have that option with the 10mp sensor. More pixels just delineates detail...and noise...more finely. Finer noise has a lower perceptual impact on our visual observation. If the baboon face is framed the same, then your gathering the same amount of light from that baboon's face regardless of pixel size. Photon shot noise (the most significant source of noise in our photos) is intrinsic to the photonic wavefront entering the lens and reaching the sensor. Smaller pixels simply delineate that noise more finely.

Jon
I am using the same source of information that you quoted for number of pixels on target - Clark.

http://www.clarkvision.com/articles/does.pixel.size.matter/

Quote: "The images in Figures 10 and 11 illustrate that combining pixels does not equal a single image. The concept of a camera with many small pixels that are averaged to simulate a camera with larger pixels with the same sensor size simply does not work for very low light/high ISO conditions. This is due to the contribution of read and electronics noise to the image. Again this points to sensors with larger pixels to deliver better image quality in high ISO and low light situations."

177
It is not true as a general statement that the more pixels on target, the better. There have to be optimum sizes of pixels and optimal numbers on target, as shown by the following arguments. The signal to noise of a pixel increases with its area:

But the signal to noise ratio of a given sensor area does not increase with increasing pixel size.
Quote

The dynamic range is also greater for large pixels than can accommodate a large number of electrons.

This is also untrue or the G15 wouldn't have more base ISO DR than the 1Dx despite having pixels with 1/14th as much area..

http://www.sensorgen.info/CanonPowershot_G15.html
http://www.sensorgen.info/CanonEOS-1D_X.html

There are factors other than pixel size that determine DR, which become the limiting factors for larger sensors - if size were the only factor then a Sony sensor would have the same DR as a Canon. However, it is basic physics that DR will eventually decrease with decreasing pixel size because of the number of electrons that can be accommodated in a well.

The noise of individual pixels is important as well as the overall noise of a particular area of sensor. That is, the overall signal to noise might be independent of the number of pixels, but the variation of signal within that area is what you actually see as noise.  Suppose you take a photo of a pure blue background. With a very low pixel density, you will see a very flat blue image. With very high pixel density, you would see lots of colour variation when you pixel peep.

178

Personally, I believe the idea of a lens "outresolving" a sensor, or a sensor "outresolving" a lens, is a misleading concept. Output resolution is the result of a convolution of multiple factors that affect the real image being resolved. Sensor and lens work together to produce the resolution of the image you see in a RAW file on a computer screen...one isn't outrsolving the other. I've gone over that topic many times, so I won't go into detail again here, but ultimately, the resolution of the image created by both the lens and sensor working together in concert is closely approximated by the formula:


It is not a misleading concept, just one that has to be used carefully. There are many processes in physics and chemistry where the end result is related to the all the components usually summed as reciprocals; e.g. resistors in parallel in an electric circuit; the overall resolution of an optical system, etc. Where those components all make similar contributions, none of them dominate and all are taking into the reckoning. E.g, a 1 ohm resistor in parallel with a 1 ohm has an overall resistance if 0.5 ohms. However, if dominates the system then the others are unimportant - the overall resistance of a 1 ohm resistor in parallel with a 100 ohm, is little different from a  1 ohm parallel with a million ohm, all very close to 1 ohm. If a lens at a particular aperture produces a point source that gives an image much smaller than a pixel, then increasing the number of pixels could be useful to increase resolution as the lens is outresolving the sensor. If the lens projects a point source to a size that is much larger than the size of a pixel, the sensor is outresolving the lens and it is a waste of time increasing the number of pixels. When the point size is similar, the situation is indeed more complicated as neither dominates.

179
Jrista,
Great images and informative discussion. I have learned a lot. Very confusing to noobs. I remember someone on CR frequently talking about better resolution being related to " number of pixels on target." So with reach limited subjects, you need either higher focal length lens or more (ie smaller) pixels per area on the sensor, to get better detail resolution. Did I say that correctly?

Yeah, that's correct. BTW, it's me who has always said "pixels on target". ;) I read that a long time ago on BPN forums, from Roger Clark I think, and started experimenting with it. I think it's the best way to describe the problem...because it scales. It doesn't matter how big the pixels are, or how big the sensor is...more pixels on target, the better the IQ. If you are only filling 10% of the frame, try to fill 50%. It doesn't matter if the frame is APS-C, FF, or something else...it's all relative.

It is not true as a general statement that the more pixels on target, the better. There have to be optimum sizes of pixels and optimal numbers on target, as shown by the following arguments. The signal to noise of a pixel increases with its area: the bigger the pixel, the greater the number of photons flowing through it and the greater the current generated, and the statistical variation in both becomes less important. The dynamic range is also greater for large pixels than can accommodate a large number of electrons. A low megapixel sensor should have very good signal to noise and DR, but poor resolution. Now, see what happens as we progress to the other extreme. As, we decrease the size of the pixel, the resolution increases but the statistical noise starts to increase as the number of photons hitting each pixel decreases per unit time. The electrical noise also increases until the inherent noise in the circuit becomes greater than that due to the fluctuation in number of electrons generated by the photons. We all experience this as the noise caused by increasing the iso setting. The dynamic range also decreases. Eventually, the pixel becomes so small that it loses all of its dynamic range because the well is so shallow it can hold only a few electrons.

So, too large a pixel gives too little resolution, too small a pixel gives too much noise and too small dynamic range. You could have a 20 billion too small useless pixels on target where 20 million would be the optimal number. Because of the above reasoning, astrophotographers and astronomers match pixel size to their telescopes. For photographers, the optimal size for current sensors pixels is around the range of crop to FF.

180
Regarding birds and DR...to be honest, I have not found that dynamic range is the issue when photographing birds.

So two golden eagles swooping in to take out a bald eagle at your back, silhouetted in the sun doesn't present a DR issue? What about bighorn rams fighting each other in uneven forest light? People wait all year for those moments, heck, they wait years. A second later, it could be gone.

Dynamic range is the single biggest issue with wildlife photography, IMHO. That's why the shadow recovery in the Sony sensors is so appealing.


Quote
Anyway, when it comes to bird and wildlife photography, dynamic range is just not an issue.


I completely disagree.  It's the issue. Are you going to sneak around a grizzly bear in the bushes to get the right angle? (that's a great way to get yourself killed). Or how about tramping in the willows on a mountain lake to get just the right light on a bull moose? (another good way to get killed).  What about when a squirrel decides to watch sunset over Glacier Point in Yosemite? Are you going to command the sun to rise from the west so you can get the good light? If you are shooting tame birds or zoo animals, maybe it's not much of an issue. But for actual wildlife? Top of the list.

The only one with the control in wildlife photography is the animal. They do what they want, when they want, and under the lighting conditions they see fit. It's your job to take the punches and get to the 12th round.

+1 My biggest mistakes are when my camera is set for point exposure for birds against a normal background and one flies by against the sky and I don't have time to dial in +2 ev to compensate or vice versa. Two more stops of DR would solve those problems.

Pages: 1 ... 10 11 [12] 13 14 ... 79