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 on: October 20, 2014, 10:41:09 AM 
Started by marcfs - Last post by marcfs

Thanks for your quick response.  I'm looking forward to your review.



 on: October 20, 2014, 09:49:19 AM 
Started by marcfs - Last post by Bob Atkins
I'm sure the 7D MkII will perform well but I can't say for sure until I get one to test. It's on my request list and I expect Canon will loan me one to test when they become a bit more available. Can't say when that will be.

I can't really comment on BIF performance with a 300/2.8 MkII and 2x MkIII because  I don't have either one and so won't be able to test that combination. From all I've read it should be better than the current 7D though. Whether it will equal the 5D MkIII or 1D-X is difficult to guess.

 on: October 19, 2014, 11:06:31 PM 
Started by marcfs - Last post by marcfs
Hi Bob,

With all of the recent 7D Mark II beta test reports, I’m wondering if you have formed an opinion on how you think the new camera will perform?
Do you have any plans/timing to test the camera? 
Would you expect this camera to effectively focus for Birds in Flight with an ef300 f/2.8L IS Mark II and 2X Mark III extender? 


 on: October 19, 2014, 03:50:20 PM 
Started by mjperini - Last post by mjperini
I think Frank is correct and the real mystery is why Thom chose to attempt to quantify the difference between a 1" Sensor and a FF sensor in STOPS.
It doesn't make sense to offer a fixed difference when the FF sensor could be anywhere from 36mp to 16mp.

We all understand that larger sensors and larger pixels gather more light
But if we took the same properly exposed picture on 1" & FF sensors with Normal f/1.8 lenses, and we printed a 4x6 or 6x9" print of each, I really don't thing one would look '2.7 times worse'  than the other. With bigger prints we'd see differentiation.
I don't know how you turn that into stops.
Thom publishes a lot of helpful information which even a Canon guy like me can find helpful. My aim wasn't to find fault but to understand.
I don't think we'll get to understand exactly what he meant, but nrither do I think it matters any more.
Thanks to all

 on: October 16, 2014, 09:21:30 AM 
Started by mjperini - Last post by Frank Kolwicz is the site that is being discussed.

The quote in the original message of this thread comes from this, the second paragraph in the Hogan review:
"But you have to remember that from a light gathering standpoint (how many photons get recorded), the 1” sensor is 2.7x worse than full frame. So we actually have a “system” that’s closer to an FX f/5 one when used in really low light. That’s not terrible, but don’t think you’re going to solve the Nikon 1 small sensor problem with just an f/1.8 lens. As the light goes down this lens is not going to suddenly turn the V3 or other Nikon 1 into a low-light master. The photosite size is just too small, and the random nature of photons is going to definitely produce noise (quantum shot noise)."

Note the last line, all of this is about noise in the images and the part about it being a problem in low light is the first clue. As to why he uses an aperture value as the metric for noise level comparison, I don't know, it's a source of unnecessary confusion, as witnessed here. I think he's confused, too.

There is a standard way of reporting this metric with various levels of technical detail, but a standard deviation number should do for simple comparisons like this. See: for example.

I've tried to think of the things that aperture can affect and come up with these:  exposure, depth of field, noise, diffraction blur and, possibly, the angle of light on sensor (related to microlens design(?)). I bet there are others that I am unaware of, but even this is an unnecessary level of confusion to bring into a discussion of sensor noise effects.

 on: October 15, 2014, 08:40:29 AM 
Started by mjperini - Last post by mjperini
Keith, others,
I did ask Thom, and he was kind enough to reply, but it was not as helpful as I might have hoped.
I think we all understand that bigger sensors with bigger pixels are 'better ' --especially in low light,
but he seems to stick to this f/1.8 Cx = f/5 Fx equivalency, but doesn't choose to 'show the work' as to how he arrived at that conclusion.

I started this thread because I thought there was some principle that I didn't understand.
Now I think he is just referring to the lower light gathering and descriptive ability of smaller vs larger sensors, and quantifying it as a certain number.
He chose not to answer my question about if pixel size was the same on each sensor, or different resolution FF sensors.
I still don't feel as though I really understand what he is saying or to what degree it is correct or not.

I'm feeling that if he had a solid technical argument he would have made it, but nor do I feel that I understand exactly what he is saying. (more than that bigger sensors with bigger pixels are better)
It seems odd to put a single concrete number on the difference between the Nikon 1 sensor and any number of different resolution FF sensors and have it always be correct???

For those that care here is my email to him and his answer: (Both in their entirety)
Thanks for an informative site, I read it regularly.
In the 18mm review I came across a statement that I'm having great
difficulty understanding.
" the 1" sensor is 2.7x worse than full frame. So we actually have a
³system" that¹s closer to an FX f/5 one when used in really low light"
Seeming to equate f/1.8 normal CX with F/5 normal Fx ?? (despite the fact
that f/1.8 is the correct exposure in both cases)
Is this just another way of saying bigger sensors are better in low light?
If the CX &FX sensors were both cut from the same wafer so pixels were the
same would this still be true??    In the real world we have Fx sensors
36 to 16MP, would both be f/5 equivalents??
By saying "in really Low Light" implies that it might not be true for
brighter light.
If it involves 'Total light falling on the sensors would that not be
proportional to sensor area whic is different by a factor of 7+ rather
than the crop factor which is a ratio of diagonals 2.7
I'm really confused here and I might not be alone.
Thanks for any light you can shed on this

Thom's Answer:
Exposure is one thing, equivalence is another. In this case, even if we
shot in bright light with a Nikon 1 with the 18.5mm at f/1.8 and shot an
FX camera from the same spot with a 50mm lens, to get equivalent images
we¹d be at f/5.

Low light would add to the woes because of quantum shot noise. A larger
photosite is going to collect more photons and produce less random results
(less noise).

Thom Hogan, writer/photographer

 on: October 14, 2014, 11:28:17 AM 
Started by mjperini - Last post by Bob Atkins
I'm not sure about the concept of "wasted" photons. All lenses and all formats "waste" photons since sensors are rectangular and lenses produce a circular image circle which is larger in diameter than the diagonal of the sensor.

It really all boils down to "the bigger the pixels the lower the noise" (at the same ISO, Aperture, and exposure time, sensor structure and electronics) and that's really all that's important.

I suppose he's commenting on the fact that some of the smaller sensor camera makers may push the availability of fast lenses as a selling point. While that's true, the fast lenses still don't compensate for the smaller sensor and smaller pixels. The fast lenses for small formats also don't provide the shallow depth of field that they do on larger formats either.

Apart from cost and convenience, there's no getting around the fact that bigger is better when it comes to pixel and sensor size from the point of view of image quality. This shows up more in low light situations.

 on: October 14, 2014, 09:49:58 AM 
Started by mjperini - Last post by KeithB
Did you try asking Thom?

He might just be wrong.

It especially is unclear since he is reviewing a fixed lens, not a sensor. While the crop sensor "uses" less photons than FF, those photons are just lost outside the chip. If you would change the focal length to an equivalent FOV, you would not "waste" any of the photons.

 on: October 13, 2014, 04:00:41 PM 
Started by mjperini - Last post by mjperini
Thanks very much.
It just didn't make sense to me. and when I tried to do more 'homework' , it became less clear.
So if it doesn't make sense to you either, I just won't worry about it.

Thanks Again,

 on: October 12, 2014, 10:05:58 PM 
Started by mjperini - Last post by Bob Atkins
Well...he says "But you have to remember that from a light gathering standpoint (how many photons get recorded), the 1” sensor is 2.7x worse than full frame".

For a start that's not true. A 1" sensor has a 2.7x crop factor. It's 13.2 x 8.8mm which gives an area of 116 A full frame sensor is 24 x 36mm which gives an area of 863 sq. mm or 7.4x the area. Therefore, for a given illumination, a FF sensor will collect 7.4x as many photons as a 1" sensor, not 2.7x. in fact 2.7 is the linear multiplication factor (lens focal length multiplier), but 7.4 is the area multiplier (2.7 squared is 7.3)

So I really don't know what he's trying to say in numerical terms. I'm not quite sure what 2.7x worse means without defining all the other parameters. What's the measure of "worse"? Is it signal to noise ratio? If so, at what illumination level? If we're talking about photons per pixel if each sensor has the same number of pixels, then the 1" sensor is 7.4x "worse", i.e. it collects 7.4x fewer photons.

The low light comes in because signal to noise ration is determined by Shot noise (based on photon arrival statistics) when few photons are collected. When a lot of photons are collected the overall noise is mainly a function of thermal noise and amplifier noise. In addition there is always some level of quantization noise, "salt and pepper" noise and possibly row and/or column noise thrown in.

Sensor noise is a rather complicated subject. Bottom line is that smaller sensors (smaller pixels) generate more noise, but the source of that noise can vary with exposure time and illumination level.

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