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Author Topic: Telephoto "reach"  (Read 9986 times)
Jonathan Wienke
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« Reply #20 on: August 26, 2005, 09:22:41 AM »
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Therefore the 20D with a pixel pitch of 6.42 microns gives us a 28% better resolution than the 5D with a pixel pitch of 8.24 microns for any same sensor size.
But that is only useful/true when one doesn't have sufficiently long glass to compose the subject properly in the viewfinder. In the majority of situations, the 5D's additional pixels can be used to capture additional subject detail in spite of the fact that they are spaced a bit further apart on the silicon. It's the same reason why my 1Ds got a lot more use than my 10D while I had it.
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BJL
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« Reply #21 on: September 02, 2005, 05:03:34 PM »
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Will the Nikon D2x continue the line? Probably not. 12MP on that size sensor is getting close to the useful limit.
Ray,
   how do you conclude that the 5.4 microns pixel pitch of the D2X is anywhere close to the limit? Even the lower quality interline CCD technology of inexpensive digicam sensors can get to less than half that spacing: around 2.5 microns is now common, which would lead to well over 50MP in DX format. (Not that almost anybody needs 50MP).
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jani
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« Reply #22 on: September 07, 2005, 07:52:00 AM »
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I just thought I'd resubmit something that I got from a Norwegian photo discussion group, regarding the cost of Canon's sensors:

Original source: http://news.techwhack.com/1878/canon-5d-is-finally-unveiled/

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Canon manufactures its sensors from 8 inch wafers (200mm dia). One 8 inch wafer yields 20 FF sensors(if there are no defects) but presently yields are at 25 %. Seventy two 1.6x (22.7x15.1mm) sensors can be made from one 8 inch silicon wafer. Yields for 1.6x sensors per silicon wafer are at 70+ %. So therefore, with each LSI batch, there are about 5 usable FF sensors for every 50 1.6x sensors. At the time the 1Ds-Mk2 was released, yields were 10 % per wafer. With fewer usable FF sensors per wafer, production costs per sensor were significantly higher and this reflected on the 1Ds's price when it was released. Canon sells far fewer 1D series bodies than the 1.6x 20D and Kiss n Digital's. Optimizing and increasing the yields is a slower process for FF sensors.

For those who don't quite get what a "wafer" might be, and can't visualize this, try the image of a wafer on this page (and if you're curious, read the article, too, although it's certainly tangential):

http://computer.howstuffworks.com/euvl.htm
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Jan
BJL
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« Reply #23 on: September 09, 2005, 02:17:14 PM »
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Ray,

a) to some extent, designing a lens of the same focal length for a smaller image circle allows improvements, but once the angular coverage is distinctly smaller than "normal", as with telephoto lenses, there is very little in it. Anyway, as I have said before, if and when there is an advantage to be had by designing a lens of a given focal length specifically for a smaller image circle, then such lenses can be designed for Canon EF-S, Nikon DX, Olympus Four Thirds etc. (Canon has done so at up to 60mm for their EF-S macro lens.)

 Photodo scores are based on measurements all the way to the edge of the 24x36mm format image circle (about 21mm radius), but for use on DX or EF-S formats of a bit less than 16x24mm, only measurements to about 15mm radius are relevant. As you have often observed, MTF is better nearer the center: see the noticable edge fall-off in Canon's MTF graphs for their 400/2.8.

Thus, if Photodo scores were recomputed for 15mm image circle radius only, the advantage for the 400/2.8 with this image circle compared to 600/4 with 24x36mm image circle would probably increase.

c) As to your price/weight comparison: given the clear cost advantages of a smaller format in other respects, a 400/2.8 for "16x24mm formats" only needs to break even on price and weight compared to a 600/4 for 24x36mm to leave the overall cost/weight advangage with the smaller format. So if a 400/2.8 is in fact a bit lighter and cheaper, this clearly gives the edge to the smaller format.

d) The above comparions are all irrelevant to overall DSLR market share predictions unless 24x36mm format bodies drop vastly in price, and so far you have provide no evidence that this will happen, only vague analogies that indicate it might not be impossible.

Optimism is fine, but please
i) say that it might possibly happen, not that it is inevitable
ii) spare a little optimism for continuing progress in sensors and lenses for smaller DSLR formats: selective optimism about the progress of your favorite format and pessimism about the far better selling alternatives makes no sense to me.
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Ray
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« Reply #24 on: September 09, 2005, 07:56:30 PM »
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If we get back to my hastily penned comment which didn't express what I was attempting to say, namely;-

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but I have no doubt that a 600/4 on a 1Ds2 would deliver higher resolution than a 400/2.8 on a Nikon D2X.
, the staement was supposed to be, I have no doubt that a 600/4 on a future full frame Canon camera with the same pixel densitiy as that of the D2X (ie. about 28MP total), would deliver higher resolution than a 400/2.8 on the Nikon D2X.

From the reviews I've read, the D2X almost has the same resolving power as the 1Ds2, but in the final analysis those extra pixels of the 1Ds2 do count for something.

Since I'm not a Nikon owner and have little knowledge of the relative merits of their lenses, I'm assuming they have lenses of equivalent type and quality to Canon's, so I'm ignoring the fact that in practice one would not be using a Canon IS lens on the D2X.

Bearing this in mind, I think it would be reasonable to state that a D2X with a lens of the quality of the Canon 400/2.8 would produce very similar results to the current 1Ds2 with Canon's 600/4. The slightly lower resolving capacity of the D2X would be compensated by the slightly higher resolving capacity of the 400/2.8, as compared with the 600/4.

But what's the advantage here, of the D2X/400mm combination. The two lenses weigh about the same (the 400/2.8 is just a few grams lighter). They cost about the same, (the 400/2.8 might be a few dollars cheaper depending on where you do your shopping). The DoF with the 400 at 2.8 is about the same as that of the 600 at f4 with the larger sensor.

There are two relatively modest advantages that I see,

(1) the 400/2.8 is a faster lens and should allow the use of a faster shutter speed with the D2X for the same DoF, FoV and resolution. But this advantage is eroded if the D2X has more noise (which it certainly does at higher ISO's).

(2) the D2X body costs less than the 1Ds2. However, anyone who is really into getting fine results from high quality lenses will find such cost savings relatively small compared to the total cost of their lenses.

If we now do a bit of crystal ball gazing, and predict a time in the near future when we have 30MP full frame 35mm cameras, then such a camera attached to a 600/4 lens should according to my reckoning should produce a more detailed image than the current D2X with the 400/2.8.

Of course, in the meantime the D2X has not stood still. Perhaps we will by then have a 22MP D2X successor. My point is, there's a 'law of diminishing returns' at work here. At some level of pixel density, there's no more detail and resolution to be had without improving lenses. The pixels then just represent over-sampling to remove the need for an AA filter.

So I repeat, if the 'derogatory' cropped format is to survive, we will need a crop of DX and EF-S lenses that are off the Photodo scale of 1-5. There's going to be a squeezing from both ends. Whilst full frame comes down in price, P&S simultaneously goes up in quality. APS-C is not in an enviable position.
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Digi-T
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« Reply #25 on: August 22, 2005, 06:23:48 PM »
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I don't see how you could be misguided when you are producing beautiful images that you and others are enjoying. It doesn't matter how you get there as long as you are  happy with your photos.

T
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Ben Rubinstein
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« Reply #26 on: August 23, 2005, 06:00:40 PM »
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Why? are there more megapixels at the edges or something?
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Sheldon N
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« Reply #27 on: August 23, 2005, 07:26:07 PM »
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On the issue of pixel density....

The 20D sensor is 22.5mm x 15mm with ~8.2M pixels. This equates to a total of 337.5 sq mm sensor size (22.5 x 15) with a pixel density of 24,252.87 pixels/sq mm.

The 5D sensor is 35.8mm x 23.9mm with ~12.8M pixels. This equates to a total of 855.62 sq mm sensor size (35.8 x 23.9) with a pixel density of 14,865.96 pixels/sq mm. Therefore, if you crop to the same sensor size as the 20D (pixels/sq mm x 337.5), you get ~5.02 megapixels.

The 1Ds Mark II sensor is 36mm x 24mm with ~16.7M pixels. This equates to a total of 864 sq mm sensor size (36 x 24) with a pixel density of 19,228.44 pixels/sq mm. Therefore, if you crop to the same sensor size as the 20D (pixels/sq mm x 337.5), you get ~6.49 megapixels.

This means that for telephoto shooting in the Canon world, the 20D is king of extracting resolution from distant subjects (provided the lens provides the resolution to do so).

As an additional point of reference, the Nikox D2x has a pixel density of 32,820.6 pixels/sq mm, and the Canon Powershot S70 has a pixel density of 183,745 pixels/sq mm. Imagine if you could mount a 600mm f/4 L IS lens on the front of that! I think that equates to a 5x focal length "multiplier", or an equivalent of a 3000mm lens - and that's before you even break out the 1.4x Extender!

There is ultimately a point for every lens where more pixels doesn't help you out with additional resolution, but based on the high quality of most telephoto lenses and the pixel density seen in the point and shoot cameras, I think we have a lot of room.

Sheldon
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Jonathan Wienke
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« Reply #28 on: August 26, 2005, 01:21:06 AM »
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To calculate the area reduction for any crop factor exactly, divide 1 by the crop factor squared:

1.6x crop factor = 1 / (1.6 * 1.6) = 0.390625 = 39.0625% of the area of a full-frame sensor. That's close enough to 0.4 for most calculation purposes.
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Jo Irps
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« Reply #29 on: August 26, 2005, 04:28:43 AM »
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Thats all correct what Lin and Jonathan said, BUT the pixel size on both sensors are not the same. That also has to be accounted for if we compare both sensors. For the 20D the pixel lenght is 6.42 microns. The 5D has a pixel lenght of 8.24 microns, which is 28.35% larger.

If we devide 12.8 megapixels by 2.56 = 5 Megapixels (as jani explained), we also have to allow 28.35% to adjust for pixel size. Hence 5 megapixel become 6.4 megapixel.
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LesGirrior
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« Reply #30 on: August 26, 2005, 10:52:44 AM »
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I'm still confused about the original subject.  

Isn't the extra "reach" on a 1.5x sensor one of their biggest advantages (in certain situations)?
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LesGirrior
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« Reply #31 on: August 26, 2005, 12:49:45 PM »
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After reading the article again, I'll add another quote to the first "Other than lower cost, there isn't much advantage".

I guess the advantages/disadvantages weigh in heavier/lighter for different people doing different work.

Lots of cool information in this thread, very interesting read.
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BJL
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« Reply #32 on: August 31, 2005, 02:49:57 PM »
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For another, it seems that few 35mm format lenses have enough resolution to exploit the potential resolution of a 30MP sensor; at least, probably not many zooms.

However, as technology progresses, it is reasonable to presume that better lenses will eventually become available at an affordable price.

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Fields like low light and high speed action photography are likely to be best handled by DSLR's with somewhat smaller sensors, smaller pixels, and shorter lenses. ...

The introduction of the 5D could lead one to think that this is the beginning of the end for the cropped 35mm format. ... there's no advantage in telephoto reach with standard EF lenses once the pixel density of the full frame reaches that of the cropped frame, as it's already done comparing the D60 with the 1Ds2, and comparing a future 25-30MP FF with the 20D.
I seriously doubt that there is a lot of room for resolution improvement in 35mm format lenses; that lens technology is too mature. The example of the discontinued 200/1.8 is not very relevant: such a telephoto lens with its narrow angular field of view is far easier to correct for abberations and such than normal to wide lenses.

And the evidence offered for the idea that larger formats will be able to match the sensor resolution (lp/mm, pixel spacing) of smaller formats instead suggests the opposite, through its time lag and price gap. The 1DsMkII matches the pixel size of the D60, but only several years later and at a far higher price; meanwhile the 20D (and D2X) again jump far ahead of the 1DsMkII for sensor resolution, and at lower prices.

What is worse, the 5D has the advantages over the 20D of being newer and far more expensive, and yet has distinctly lower sensor resolution (and lower frame rate.)


I am puzzled why some people ignore all trends in order to cling to the the belief that larger DSLR formats will someday offer something for nothing: sensors of more than twice the area, with the same pixel pitch and so more than twice as many photosites, and lenses with more than twice the image circle area yet with the same resolution (lp/mm), all at no significant price increase. And all this is meant to happen despite the funding handicap for the larger formats of having far lower sales revenues than the smaller DSLR formats from which to finance all the required R&D.
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BJL
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« Reply #33 on: September 01, 2005, 06:17:37 PM »
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... at some point, little purpose will be served by increasing pixel density.
I just deleted a longer reply in favor of this: far before DSLR formats reach any technological limits on pixel density, they will be beyond the resolution/sharpness that the great majority of SLR users will bother to pay extra for, and larger 35mm format sensors will always cost more by enough to discourge those customers from buying them. Indeed, I suggest that the Nikon D2X is already beyond that level of image quality, and the same resolution will soon be possible in a lower level DX format body at far less than the cost of the 5D, for the same reasons that the 5D can cost so much less than the 1DsMkII.

So the pursuit of "ultimate pixel count limits" with larger formats will be the domain only of a small minority of SLR users who crave such extremes enough to actually pay for them, not just to fantasize about them in internet forums.

As a reality check, who has seen D2X prints, or even 1Ds prints, that reveal the resolution limits of their sensors? How large were those prints, and how close did you have to go to see the problems? (No test pattern viewing please!)
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jani
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« Reply #34 on: September 02, 2005, 11:30:01 AM »
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Maybe my assumption has at least one major flaw, but you haven't explained it to me yet.
Well, the explanation was further down in the same post that you so delicately snipped.
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Jan
BJL
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« Reply #35 on: September 02, 2005, 01:04:27 PM »
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What lenses do you think are missing for EF-S mount that are relevant to more than a small fraction of SLR users?
BJL,
Sorry! You've just shot yourself in the foot.

For the APS-C format to survive it needs more than a small minority of adherents.
Ray,
  you must be totally out of touch with the current patterns of lens usage if you think that all but "a small minority" demand fast wide to normal prime lenses like 24/1.4 or 20/1.4.

Or otherwise, you are right, but Canon, Nikon, Olympus, Pentax, etc. are all wrong, which I very much doubt. Because NONE of those companies are offering any such fast short focal length primes for their mainstream DSLR formats, even though such lenses are quite feasable to make; such lenses are lacking not only for EF-S, but also for Nikon's DX, which is solidly aimed at covering the professional level, and are also lacking for Four Thirds, Pentax DA and Konica-Minolta DT.

That leaves only your example of the 400/2.8: but Canon and Nikon do both have 400/2.8 lenses that are perfectly usable with EF-S and DX bodies! Surely you know that at such long focal lengths, nothing is gained by designing for a smaller than 35mm format image circle? Or do you believe once again that you are right about lens needs and every major camera/lens maker is wrong, in that every one of them is failing to produce new smaller image circle lenses at focal lengths beyond 60mm (60mm minimum in the case of zoom lenses.)

P. S. See my forthcoming reply on the "cropping myth" to learn why it makes no sense to produce lenses beyond about 60mm with smaller than 35mm format image circle.
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EAD
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« Reply #36 on: September 02, 2005, 02:37:13 PM »
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Fascinating thread(though a bit complicated to follow when english is not your mother language...)

Something that has been on the back of my head now, and has been "insinuated" here:

No doubt, APS sensors have their advantages, specially when it comes to long reach and sport-wildlife shooting(my max. length is a 300mm and very often I find it wanting for my water-sports shooting on my 20D).A lot has been said about pixel count/FOV so..

I suspect if Canon released an APS sized camera, with a pro spec body(not necesarily so big as the 1 series), weather sealed, 100% viewfinder (and bigger if possible..), RGB Hystogram, spot-meter,in the range of the 10-12MP, and a high frame rate, we would have....a D2X!!! (and a #### of a machine, very, very, very apealling to many..).If only I didnt have all that money invested in Canon Glass!!!

Maybe, maybe...

Fascinating times for Techno-freaks!!

Happy shooting.

Erik
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Ray
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« Reply #37 on: September 04, 2005, 01:43:08 AM »
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such lenses are lacking not only for EF-S, but also for Nikon's DX, which is solidly aimed at covering the professional level, and are also lacking for Four Thirds, Pentax DA and Konica-Minolta DT.

Indeed they are lacking, which seems a bit odd considering the one stop (or more) shallow DoF disadvantage of the smaller format and its need for higher resolving lenses because of its (usually) higher pixels density.

I can only speculate on the reasons, but I think high quality primes in general are only affordable when there's a large market for them. How many times have you read posts on this forum and others about the indecision of committing to the purchase of an EF-S lens which will be no use with FF 35mm? The impression I get is that most owners of APS-C Canon DSLRs bought their camera because they couldn't afford a 1Ds or 1Ds2, or at least justify the purchase to their spouse. I just don't feel that most of them, if money were no object, would choose an APS-C format in preference to FF 35mm.

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That leaves only your example of the 400/2.8: but Canon and Nikon do both have 400/2.8 lenses that are perfectly usable with EF-S and DX bodies! Surely you know that at such long focal lengths, nothing is gained by designing for a smaller than 35mm format image circle?

No, I didn't know that. Could you explain why. I recall reading that NASA considered the Zuiko 300/2.8 designed for the Olympus 4/3rds format, the finest lens it had ever tested. I assumed that part of the reason this lens is so good is because it was optimised and corrected for a smaller image circle.
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Ray
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« Reply #38 on: September 04, 2005, 03:53:12 AM »
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Essentially all lenses that give a field of view less than about "normal" crop the image formed by the lens, with the degree of crop depending mainly on how narow the desired angular FOV is, independent of format. Roughly the FOV gathered by most such lenses is about 40 to 50, projecting an image circle far larger than needed for the format, and the hidden "in-the-lens" crop factor is the ratio between that image circle angular coverage and the smaller angular coverage of the sensor/film.

BJL,
This is an interesting piece of arcane information but also a fine example of a specious argument (well done! ).

If one wishes to be completely literal about this, it's rarely possible with any standard camera smaller than 4x5 to take a shot without cropping the image circle. A rectangle cannot fit into a circle without cropping parts of the circle. Whether or not the cropping is done internally through the lens design, the image circle must be cropped.

However, 'cropped format' has a different meaning, and not derogatory. It's the cropping of the image circle to a greater degree than was anticipated during the lens design.
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BJL
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« Reply #39 on: September 06, 2005, 06:57:32 PM »
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BJL,
This is an interesting piece of arcane information but also a fine example of a specious argument ...
Ray, if you are going to accuse me of specious arguments, please at least make a pretence at showing the fault in my argument. Or are you now going to suggest that "specious argument" is not derogatory?

I repeat: a 200mm lens in DX format and a 300mm lens in 35mm format each take an image of about 40 angular field of view and record a portion of it with about 8 field of view, which measn that they use abot the same fractio of the image. Please explain how one format is cropping more than another.

Or to get straight to practical issues, please explain how the image quality of the 300mm, 35mm format option should be expected to be noticably better than that of the 200mm, DX option?

Let me reapt anothe pont that yopu have ignored: longer telephoto focal lengths are almost always achieved essentialy but putting a teleconverter into a lens of shorter focal length, so that the resolution in lp/mm decreases in proportion to the increase in focal length, giving about the same resolution in lp per picture height. (Your low opinion of the effects of teleconverters on resolution has been noted already in these forums.)
For example, compare the MTF curves of the Canon 600/4 to those of their 400/2.8 over the central part out to about 16mm, which is what would be used in a 1.5x crop. The 400/2.8 looks far better, rather than suffering from the crop.

If that is so, how is using a longer telephoto focal length and larger format expected to give a significant resolution advantage?
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