October 20, 2014, 07:52:09 PM

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Messages - Sella174

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Just because a sensor is larger doesn't mean it has less noise and indeed, if you were to take two sensors that used pixels of the same design then both sensors would have equal noise.

But is that not what I've been saying all this time?

If you want to compare sensor technologies, then the size of the sensor is less imporant.  If you want to compare a FF camera to an APS-C camera, then it's essential to include the entire area of each because those are the defining characteristics of each.

So what's your intention?  Are you comparing sensor tech or actual cameras with FF and APS-C sensors?

I am comparing sensor technology, whilst neuroanatomist responds by comparing actual camera sensors. Very confusing.

Um, if you're excluding the light outside the center (crop-equivalent) area, you're not comparing a FF to a crop-frame; you're comparing a crop-frame to a crop-frame.

More correct would be say that one is comparing a crop of a "full-frame" sensor to a "crop-frame" sensor.

The comparison is absolutely meaningless unless you compare the full area of the FF against the full area of the crop-frame.

But even that is a meaningless comparison, because a "full-frame" sensor is physically larger in area than a "crop-frame" sensor and thus always illuminated by more light. For this type of comparison to have any real meaning, the two sensors must be normalized ... somehow.

Lenses / Re: This thing's gotta go!
« on: June 11, 2014, 05:31:56 PM »
Nikon 35-70mm f/2.8 AF-D Macro - fully disassembled, I was able to fix what was causing the zoom and focus to not be smooth, however, I was not able to reassemble it (I like fixing Canon gear much more)

I sometimes fix Nikon lenses and, yes, yuck to reassemble. You have to get all the gears and such correctly aligned in the correct order or it won't go back together. Very, very troublesome.

So it boils down to these two points?

Three points, actually. You forgot the +36MP "full-frame" camera, with lenses to match. (Oops, that's a fourth point.)

So you're wrong even about your own behavior.  Interesting.

OK, since my understanding is apparently wrong ... and I want to learn.

Given a "full-frame" sensor and a "crop-frame" sensor, made of the same "sensor technology", i.e. same size photosites, same A/D converter, same everything except area.

The statement is that a "full-frame" sensor gathers more total light than a "crop-frame" sensor.

Explain to me how and why the "full-frame" sensor collects more light in the centre area of the same equivalent size as the "crop-frame" sensor, than does the "crop-frame" sensor; or, stated differently, how and why does light falling in the area on the "full-frame" sensor outside the "crop-frame" equivalent centre area affect the amount of light gather within the designated centre area of the "full-frame" sensor, thereby causing said designated centre area of the "full-frame" sensor to gather more light than the "crop-frame" sensor.

I'm not really sure what your point here is ...

The point was simply that "full-frame" is not the ultimate objective in camera ownership for everyone who is not a "soccer-mom" and that some enthusiasts are quite happy with "crop-frame" cameras. I guess in the same way some are not content with the current 20MP'ish "full-frame" offerings from Canon, even though most "full-frame" users are quite happy as it stands.

Wrong.  Care to try again?

Who cares? I'll just move the lens forward, as all that does is change the aesthetic perception.  :P

Changing the distance would alter only perspective, an aesthetic change with no relevance to the sensor comparison.

No further comment ... it is futile.

Instead, you'll suggest (oddly since you have zero information to go on regarding how I choose glass) that I either don't care about color or image quality ("I have found that L-lenses generally have better colour and more pleasing image rendition than non-L-lenses (made by Canon). But I suspect you don't view lenses in this light.") or that I am somehow incapable of learning a concept ("If you don't know why this is desirable, then you also wouldn't understand it if I explained it to you). I prefer to speak plainly.

At some point you were unwilling to even consider my opinions, but simply followed that of the crowd. This situation seems to have changed. You still don't have to agree with me on anything, everything and this.  ;)

Don't retrofocal designs increase the back focus distance? How does reducing the back focus distance eliminate the need to increase the back focus distance? If the goal is a shorter back focus distance, then you are talking telephoto, not retrofocal, right? Maybe not.

Broadly speaking, that is correct. However, the need for a retro-focal design is linked to the focal length of the lens and the desired image circle it must project.

I'll explain this with an example: a 50mm lens is a 50mm lens because that is the distance from the front element to the focal plane (e.g. the sensor or the film). Now, in the real world this 50mm generally includes a fair bit of the space inside the camera ... where the mirror swings in a Canon DSLR. Not enough space, so we must move the lens forward, i.e. increase the back focus distance. The answer is the retro-focal design.

Now, as the EF-S mount has a shorter back focus distance (smaller mirror), one could design some lenses without resorting to a retro-focal design. (This is also why mirrorless is so appealing in terms of lens designs.) Or use less of a retro-focal design. Less elements within a lens is always better ... up to a point, anyway.

Another factor is the effect that as the image circle becomes smaller, as with an APS-C sensor, the minimum focal length where one must start using a retro-focal design also decreases.

Plus, the EF-S mount allows for a fair amount of cheating in terms of the size of the optics, but that's another story.

You're suggesting that if I crop an APS-C FoV from a shot with my 1D X, that the IQ of the resulting 7 MP image will be the same as the IQ an uncropped image (assuming I adjusted the framing with a zoom lens or changing the distance).  Sorry, that's simply not true.   

Let's not assume, because by doing that you are changing the parameters of the experiment whilst conducting said experiment by introducing unquantified optical variances.

Redo the experiment. And please leave DoF at home.

In other words, not      usefulness on APS-C formats      corner quality      color quality. Now we have a reasonable idea of what moving the goalposts is. And congrats on being preposterously arrogant!

Your question was: "What do you expect to get from an EF-S L prime that you can't get from an EF L prime?" Therefore I did not mention the current attributes of L-lenses, because you specifically asked for what it was that I couldn't already get from using EF L-lenses and thus, for instance, good colour rendition and excellent corner quality are implied by default. And, even though I most definitely am "preposterously arrogant", I still won't stoop so low as to slap derogatory labels on you.

Honestly Sella, are you trying to be the representative of the niche of the niche of the niche group? The group of Canon users who, just will not agree to anything or anyone and want the most bizarre products to be produced by Canon, and only make up 0.00............1% of Canon users?

Read what I wrote, not what others told you that I wrote. Then learn to think for yourself, instead of having others think for you.

Finished? Now go look up the profit Canon's photographic division made last year and calculate what is 1% (the figure you so randomly plucked from others' posts) of that amount. That is the amount of additional money Canon could have made on each and every product made specially for us "niche of a niche of a niche 1% group of Canon users". Instead, we're spending that amount as a baseline elsewhere.

Think for yourself. Am I right or am I wrong?

So total light doesn't matter for image noise, only pixel size?  You do, indeed, have a sense of humor…perhaps that is some compensation for your poor understanding of how sensors work.

You stated that "larger sensors collect more total light". By using the term "sensors", you imply the whole sensor, i.e. all the photosites together. Then you use the phrase "total light", which implies all the light illuminating the total area of the sensor.

Now, because a "full-frame" sensor is larger in area than a "crop-frame" sensor, by simple geometric calculation a "full-frame" sensor indeed does collect more "total" light than a "crop-frame" sensor. BUT, the amount of light collected by the "full-frame" sensor for the area in its centre equal in size to that of the "crop-frame" sensor, is the same amount of light that the "crop-frame" sensor collects in totality.

(For the sake of the following, assume both sensors have the same end-resolution of, say, 18MP.)

The rub comes with the size of the photosites. As we stand today, the size of the photosites of a "full-frame" sensor are larger than those of a "crop-frame" sensor. This means that one photosite of a "full-frame" sensor collects more light than a photosite of a "crop-frame" sensor simply because it has a larger area that is illuminated. On a "crop-frame" sensor, that same area equal to the size to one photosite of a "full-frame" sensor is shared by several photosite. Thus they also have to share the light falling on said area.

This means that a "full-frame" sensor with the same photosite density as a "crop-frame" sensor will perform equally to the "crop-frame" sensor in terms of image quality ... and, of course, vice versa.

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