September 23, 2014, 02:26:23 AM

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Messages - Sella174

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EOS Bodies / Re: Official: Canon EOS 7D Mark II
« on: September 22, 2014, 08:21:46 AM »
Finally Canon releases the camera we should have had years ago. Now for the (weather-sealed) EF-S L lenses to match ...  ;)

Well, if the lens is up to the job, obviously any high megapixel count sensor at a low ISO setting will provide more image detail than a bigger sensor with a lower megapixel count at the same ISO setting with the same lens.


Thanks for that lengthy reply. I now see where the problem lies: we are comparing different things. Oh, and thanks also for attributing statements which I never made to me.  ;)

If Sella wanted to compare tech he should have said so, but he used the term "full frame;" by definition, that is a sensor with dimensions equal to a frame of 35mm film.  That is the defining characteristic of "full-frame."

It is in truth neuroanatomist who keeps insisting that a sensor of "full-frame" size has better "characteristics" than an equal sensor of "crop-frame" size, e.g.

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.   


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.

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