October 01, 2014, 04:29:18 PM

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Messages - Sella174

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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.

You've moved them so much I've lost track -- where was that again?

Actually, I only moved them once: back to their original positions. It is you and your friends who keep moving them about due to assumptions based on hero-worship and indoctrination.

don't forget that these ef-s primes will be priced like ef primes if they did exist.  So a market of folks that won't spend more than $800 on a body will obviously be more than willing to spend $1500 on one lens.

Price check on the 70D is about $1000. The upcoming 7D2 will be, what, about $1500. Whatever, because the price of the camera is irrelevant to this "EF-S L-prime" discussion. The fact is that such lenses would be, as some have said, an "investment" that will last several cameras.

For example, given the sales volume difference, it's possible that EF-S L primes would be more expensive than comparable EF L primes.

I was not asking for Canon to make EF-S lenses for which there are already EF lenses available. I was asking for lenses for which there are no equivalent EF primes, like for example an EF-S 35mm f/1.8 L MACRO or an EF-S 10mm f/4 L or an EF-S 75mm f/1.2 L ... or an ...

He's going to tap-dance around this as well: he'll say sure, a bigger sensor captures more light, but if Canon put Sony-quality sensors in their APS-C cameras that would be almost as good as Canon's FF (other than 1DX).

I think he's moved the goal posts all the way to Antarctica already, let's see if how long it takes to hit the next continent.

What happened? You're suddenly back at stage one.

Um, okay, but that's not what I asked. At least, that's not what I intended to ask. Let me add the missing letter to my question:

What do you expect to get from an EF-S L prime that you can't get from an EF L prime?

You are moving the goalposts, but what the hey ... I'll walk right into it, so's you-know-who can have a giggle.

An EF-S L-prime would take advantage of the shorter "back-focus" distance. This could possibly eliminate the need for a retro-focal design in certain focal lengths, as an example. If you don't know why this is desirable, then you also wouldn't understand it if I explained it to you. And I suspects you don't, which why you also cannot fathom the point of EF-S primes (L or not).

Larger sensors collect more total light ...

True, because a "full-frame" sensor covers a larger area (864mm2) than a "crop-frame" sensor (337.5mm2). Basic geometry.

... meaning better IQ.

Wrong, because it is the size of the photosites (and cross-talk between them) that determines image quality, together with the lens.

Feel free to argue the point, but you'll only succeed in making yourself look more foolish.

You're still at stage one, neuroanatomist. Others are already at stage four. Come on, hup, hup, hup!

I'm sure he'll move the goalposts again, though.

Yes, back to their original positions!

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