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Author Topic: Telephoto "reach"  (Read 10267 times)
Ben Rubinstein
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« Reply #60 on: August 23, 2005, 03:36:15 PM »
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If you crop the picture from the 5D by 1.6 (like the 20D sensor) then you get exactly 8 megapixels. In other words you can have the best of both worlds.
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Digi-T
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« Reply #61 on: August 24, 2005, 04:38:11 PM »
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The image is not cropped in the same way that you crop an image in an image editor by literally throwing away pixels.
Yes it is, if you are comparing two different formats with the same pixel density, such as the Canon D60 and 1Ds2.

Shoot the same scene with both cameras, from the same position using the same lens. The D60 image should be identical to the 1Ds2 image cropped in an image editor to the same size as the D60 image, ie. by literally throwing pixels away.

Note: I don't mean identical with regard to every characteristic, such as color hue and balance, and noise at high ISO etc., but identical with respect to resolution at base ISO.
Ray, I re-read your post and I now understand where you were coming from. We were just looking at things a little differently. You make some good points.  Smiley

T
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Jo Irps
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« Reply #62 on: August 26, 2005, 08:56:29 AM »
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Of corse you are right Ray.

But whatever the pixel size is, we always have to calculate the pixel pitch, because that is the size of that tiny little square which we are going to see seamlessly besides the next little square. 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.
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BJL
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« Reply #63 on: September 01, 2005, 01:01:13 PM »
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Ray,

   I am glad we seem to agree that this is just about a larger minority of high budget SLR users like you changing to 35mm DSLR format, rather than an absurd prediction that the smaller DSLR formats wil cease to dominate overall digital SLR sales.

A few facts though:
- the price difference between the 20D and 5D is about US$1800, well over the $1000 in your $500 vs $1500 comparison. Sensor price difference seems to be the main factor in this US$1800 difference.

- The format price difference goes up if you wish to get the much talked about better high speed performance in telephoto shots, because to use the same ISO with a larger format needs a longer focal length but the same minimum aperture ratio. Compare a 200/2.8 to a 300/2.8 for price (and weight), for example. What is more, the same minimum aperture is more often not even available for the longer focal length: where Nikon DX can uses 200/2, 300/2.8 or 400/2.8, the equal f-stop 35mm same FOV counterparts of 300/2, 450/2.8 and 600/2.8 do not exist. If instead you use the same focal length with the larger sensor and crop, all the image quality advantages of the larger sensor are cropped away.


Presumably your prediction about the smaller DSLR formats (please, can we avoid the inaccurate and derogatory term "cropped format"?) needing "a full range of high quality EF-S lenses" only refers to Canon's EF-S mount DSLRs; the survivial of DX format, Four Thirds, etc. do not rely on EF-S lenses!

Even then, you have not offered the slightest evidence that the price penalty of the larger format will ever be low enough for the majority of SLR buyers: US$1800 is far, far too much: it is more than the gap between entry level and top of the line in 35mm film SLRs! Looking at film SLR prices, every few hundred dollars leads to a substantial reduction in sales volume.

Finally, the current range of lenses for EF-S mount DSLRs is probably adequate for the great majority of SLR users. What lenses do you think are missing for EF-S mount that are relevant to more than a small fraction of SLR users? Hint: mainstream SLR lens usage these days is dominated by "non-pro" zooms slower than f/2.8, along with primes at the wide and telephoto extremes of f/4 or slower, and maybe macro lenses. Everything else is low volume.
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jani
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« Reply #64 on: September 02, 2005, 05:19:11 AM »
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There should be no doubt that whatever the costs and difficulties that are currently associated with 35mm sensor production, they will prove to be a temporary state of affairs. That's the nature of technological progress.
Your assumption has at least one fundamental flaw.

The same advances that will make 35mm sensor production easier/cheaper will also benefit smaller sensors.

That is just as inescapable as the famed "technological progress".

You just can't get away from the following two problems without a fundamental change in how sensors are made:

 - larger chips/sensors waste more of a silicon wafer
 - larger chips/sensors have a higher probability of defects

Whether the price differential will become substantially lower is mostly guesswork.
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Jan
BobMcCarthy
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« Reply #65 on: September 02, 2005, 01:32:10 PM »
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The businessman in me says "Canon screwed the pooch" in their latest direction. Did they waste the R&D (time) to release a basic spec FF.

I can't see any "significant" cost reduction in the cost of FF chips from here. The HT industry doesn't work that way. Thats been stated many times before. Maybe higher density and more Mpxls, but not reduced cost.

But as competitors release cameras in the 11-13 mpxl range with far better bodies (lets face that the 5D has a low cost/spec prosumer body)  initially at a 30% discount (pro spec'd body) and ultimately a 60% discount (prosumer body), the sales tide will turn against FF

Is 12 mpxl's (give or take) enough?? Most will say so.

Volume production of FF chips will help to reduce the cost/price of the 1DsII and likely make it more competitive with the D2x so I can forsee price reductions/rebates of the 1DsII or more likely a 1DsIII as this is more canon's style.

I fully expect Canon to release a pro DX chipped camera to compete on cost with Nikon.

I expect Nikon and Canon to explore ways (primarily in software) to make the image capture from the Dx chip more palitable . Noise reduction, lens aberation correction in software is coming (Nikon). Canon will  fix the nasty edges with FF digital. An excuse for new camera models BTW.

In the end, the cost differential will make the difference between who ends with the lion share of the business. We've gotten close enough to the "end game" with regards to image quality, so price differential becomes a significant factor in the decision to purchase.

Bob
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BJL
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« Reply #66 on: September 02, 2005, 05:30:14 PM »
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The term 'cropped format' is not derogatory but precisely meaningful and provides an indication as to why it will probably not survive. ... a 20D with an EF lens is indisputably a cropped format.

The cropping myth.

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 40º to 50º, 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.

Thus for example, a 300mm lens used in 35mm format crops the image by the same proportion as a 200mm lens used with DX format, as each crops down to about 8º FOV. In fact, with true telephoto lens designs, a 300mm lens is internally something like a 200mm lens at the front, but with greater magnification in the diverging rear elements, like a built in teleconverter. (That "built-in teleconverter" is the definition of a true telephoto lens design.) And like any teleconverter, what it is effectively doing is cropping, since the extra enlargement make more of the image formed by the front part of the element fall outside the sensor.

The cropping fallacy comes from comparing what happens when the same focal length is used with different formats, instead of the relevant comparison which is between lenses that give the same FOV in the respective formats by using different focal lengths. Longer focal length telephotos have a greater degree of hidden "in lens" crop.

When lenses of the same FOV are compared, one sees that all the shorter lens does with a smaler sensor is compress the same light from the subject into a smaller part of the focal plane, so that the same light is gathered by the sensor, with no more or less cropping loss.


P. S. How can you say your wording "cropped formats" is not derogatory, and then claim that this putative cropping is such a problem that it "provides an indication as to why it [EF-S] will probably not survive."
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Ray
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« Reply #67 on: September 07, 2005, 09:42:08 PM »
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Sorry! I'm also guilty of confusing the issue. In the example I mentioned there probably wouldn't be much in it.

The point I'm making, which BJL seems to indicate is fallacious, and he might well be right, is this.

It should be possible to design a higher resolving 400mm lens for a smaller format, such as the D2X, than the current 35mm 400mm lenses, because of the smaller 'working' image circle required. Futhermore, if the APS-C format is to continue to compete with the larger full frame format as pixel density continues to increase in both formats, the smaller format will have to rely upon superior lens performance.

BJL seems to be saying that lenses longer than about 60mm rely upon a built-in teleconverter to achieve that telephoto effect, and we all know that teleconverters decrease resolution.

Since I'm not a lens designer, I'm having trouble understanding this concept, particularly in relation to Photodo results which show that Canon's sharpest lens is the 200/1.8. This lens is sharper at f4 than any of Canon's 50mm lenses at any aperture.

Canon's 400/2.8 IS weighs as much as the 600/4 and is only marginally less expensive.
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LesGirrior
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« Reply #68 on: September 10, 2005, 05:07:26 PM »
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APS-C is not in an enviable position.
Consider the use of these smaller sensors in "beginner" dSLRs.  More and more people are buying dSLRs like the Rebel and d70, for them they get quality better than film with smaller, lighter lenses for cheap.  I have a feeling Canon sells a lot more Rebels than any of their pro/high end equipment.

For average joe, "cropped" sensors are nothing but advantage.
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BJL
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« Reply #69 on: September 15, 2005, 11:42:08 AM »
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It wouldn't surprise me if this new Sony can produce sharper images than the 20D with nearest equivalent Canon zoom lens, and images with equally low noise at equivalent ISO settings.
And it wouldn't surprise me if Sony uses essentially the same sensor technology at the slightly larger DX format for the next Nikon DSLR, so returning to 12.5MP of the D2X, but without the fancy four channel read-out and such needed for its higher frame rate capabilities. That could produce the much rumored "D200" with price under US$2,000. A DX format sensor is less than 20% larger in area than the R1 sensor, so the sensor cost will not be so much greater.

If so, I wonder how that would compare to the 20D? To return to the original topic of this thread, it would probably allow a mixture of "finer grained" prints [meaning higher ppi] and increased telephoto reach with a lens of the same focal length through greater cropping latitude.


In fact, subtracting the cost of the lens in the R1, replacing the EVF system by a reflex mirror and pentamirror OVF, Nikon and Sony could probably put such a 12.5MP DX format sensor into a bare bones, low frame rate, entry level DSLR for about US$1,000, but I do not expect that, at least for a while.
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Ray
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« Reply #70 on: September 16, 2005, 06:38:30 PM »
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BJL,
The next level of P&S development is the design of sensor and lens as an integrated package including DXO type corrections. Not that I have any insider knowledge of what's on the drawing board. I'm just using my nous.

The impression I'm getting from your erudite comments is that major sensor manufacturers churn out the chips and lens manufacturers do their best to fit the lens to the sensor.
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BJL
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« Reply #71 on: September 20, 2005, 12:13:53 PM »
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BJL,
 ...
The impression I'm getting from your erudite comments is that major sensor manufacturers churn out the chips and lens manufacturers do their best to fit the lens to the sensor.
Ray,
    first "arcane" and now "erudite"; I am flattered!

The trend of adapting lens designs to the needs of new sensor technology is fairly strong and persistent; it has been going on at least since Leica attacked the problem of designing new lenses for a new type of sensor, the tiny 24x36mm frames of film with new, higher resolution emulsions.

Canon does this not only with its new short back-focus EF-S designs but also with quiet redesigns of the rear elements of some EF lenses, to reduce flare problems due to the high reflectivity of most electronic sensors. In a smaller way, Canon's now completed series of F/4L zooms is a response to new sensor characteristics: several stops more usable ISO speed than film, allowing many photographers to trade one stop for high quality lenses that are lighter, less expensive, and offer wider zoom range than the old f/2.8L series.

Of course it goes a bit the other way too: the designs of sensors in most current DSLRs are clearly partly chosen (format size) for adequate compatability with existing lenses. Even if only as a transitional step while a new range of lenses is developed.

By the way, DXO style corrections are already offered as part of the Four Thirds system: lenses communicate the neccesary information to the camera, allowing some corrections to be done in camera, with others like distortion correction doable later on the computer. Nikon also offers some of this, for the special case of rectilinear correction to images from its 10.5mm DX fish-eye lens.
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