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Author Topic: Is It Just Me or ...  (Read 18040 times)
Ray
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« Reply #80 on: November 10, 2008, 06:07:26 AM »
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Quote from: Dan Wells
Another question that comes up here is "How large is your printer?" The differences above 12 MP really don't show up on less than a 17 inch printer, and can't possibly show up on any monitor or projector while looking at the whole image. 17 inch printers are big, heavy beasts that are a major commitment to live with - they sit on a table, but barely. 24 inch printers are worse (on the order of figuring out where to put a small upright piano!). If you have a printer that size and print to its capability, the highest resolution cameras (including Hasselblads, Phase backs, etc...) might make sense. If it's all going to be printed 8x10 or shown on the web anyway, any camera works (with the exception of dynamic range where the 8x10 print (on a really good printer) is concerned - it IS possible to play "spot the Hasselblad" on an 8x10 print of certain images, but it'll be the 12 stops of dynamic range that gives it away, not the resolution). If you're doing anything exclusively for electronic display, whether monitors, projectors or whatever, they're all not only under four megapixels (and 4 MP is a 30 inch monitor, a more than slightly exotic beast), but also have only about five or six stops of dynamic range - a really good compact is plenty for even a 30 inch monitor.


                      -Dan

That's a good point. I've got an Epson 7600 24" wide format printer, and that fact influences my comments. It seems a bit odd to me that any photo enthusiast would spend time watching relatively low resolution images on a 42" or 50" HD LCD or Plasma TV, but not have a printer that can even approach that size.

I like my prints large, like a painting.
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ErikKaffehr
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« Reply #81 on: November 10, 2008, 02:23:19 PM »
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Hi,

I'm not a Canon shooter, but I just got a pretty good test on the Canon 50D (from the Swedish monthly Foto). They have discussed the resolution at some length. They state that normally no advantage of resolution can be seen between the 40D and the 50D. They needed the best lenses and the best aperture to extract maximum resolution from the 50D. Their testing is based on Imatest. Of the three lenses they tested the 50/2.5 macro was the best, followed by the Sigma 18-50/2.8 and the Canon EF-S 17-55/2.8IS. Even with this combo they needed A2 (40x59 cm) prints for the difference to be visible.

My interest is more with Sony, yesterday I downloaded a test image from Imaging Resource for both the Sony A700 (12.5 MPixel) and the Sony A900 (24.6 MPixel). On screen the A900 simply blows the A700 away. No comparison! But I also made one A2 (40x59cm) prints and they were pretty close. I can tell them apart from arms lengths distance, but there is not a lot of difference. In this comparison the A900 had a slight advantage because I could download a "raw" image but only a JPEG for the Alpha 700.

The way I normally do comparisons is that I scale up the images to a common size, in this case to about 46x70 cm at 240 PPI and look at actual pixels. I enclose a screen dump from that comparison. I'd suggest that the difference between the Canon 40D and the 5DII would be similar.

Best regards
Erik

[attachment=9588:A700_vs_A900.jpg]

Quote from: JohnKoerner
Thanks Ray.

Question though: are "sharpness" and "resolution" the same thing? I honestly don't know.

The 50mm prime you speak of is considered "sharp" on the 40D but not so on the 50D ... and my (admittedly limited) understanding is because of resolution. Not sure what that means exactly, but that is the complaint I keep reading. Lenses like to 100 macro are "sharp" too, but provide better resolution, which the 50D maximizes. At least that is my layman (not really sure) interpretation of what I am reading.

On the flipside, though, the positive news I really do understand is that the 50D has already gone down in price by $200 within the last week, thanks to the bad review, so maybe I should thank DP Review rather than be angry  

Jack
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JohnKoerner
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« Reply #82 on: November 15, 2008, 10:53:57 AM »
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Thank you to everybody for your thoughtful responses  

Jack




.
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ErikKaffehr
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« Reply #83 on: November 15, 2008, 03:23:05 PM »
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Ray,

All this are good points, but I would also add that a 200/1.8 is simply much more glass, and probably expensive glass, too. In long lenses chromatic aberration is one of the major obstacles and very expensive glass, like CaF2 is used to eliminate it. Normal and short tele lenses are relatively easy to build so they often have very good performance for a reasonable price.

As far as I understand it is hard to build large aperture lenses, especially with a wide angle of view.

Best regards
Erik  

Quote from: Ray
There seems to me to be great confusion as to the significance of the claimed higher resolution of expensive, high quality glass. The best and sharpest lens that Canon ever made, the 200/1.8, that's now discontinued and is very heavy and used to cost several thousands of dollar, is only marginally sharper than the humble 50/1.4 standard lens that costs just a few hundred dollars.

The reason such lenses (as the 200/1.Cool are so expensive is that they are sharp at wide apertures. That's where the expense comes in. It's very difficult to make a lens that is as sharp at F2.8 as it is at F8. The 200/1.8 is sharpest at F4, but only marginally sharper at F4 than it is at F8, and only marginally sharper at F8 than the 50/1.4 at F8.

If we look at the potential increased resolving power of the 50D sensor (compared with the 40D) we find that it should be about 22%. (Twice the pixel count equates to a 1.4x increase in resolving power, and a 1.5x increase in pixel count equates to a 1.22x increase in resolving power, in terms of lp/mm.)

However, (and it's a big however), this potential 22% increase in resolution is only achievable if the lens used also has a 22% increase in resolving power. Resolution in the image is always a product of lens resolution and sensor resolution.

We don't seem to have much MTF information on lenses nowadays, but there is no lens that was ever tested by Photodo that had even nearly 22% more resolving power than a basic and inexpensive prime such as the Canon 50/1.4, comparing lenses at their sharpest aperture, whatever that may be. We might be looking at a 5% increase at best and typically a 2 or 3% increase.

The real advantage of a very sharp, expensive prime is that it allows you to use a faster shutter speed and get a shallow DoF without sacrificing the sharpness that can always be obtained at F5.6 and F8. The 200/1.8 is significantly sharper at F1.8 than the 50/1.4 at F1.8. That's what you pay for. Faster shutter speeds usually result in sharper images, and a shallow DoF tends to enhance the appearance of sharpness at the plane of focus, by contrast with what's out of focus.

There would be little point in buying expensive glass to use with the 50D unless you need or want the faster shutter speeds and shallow DoF that such lenses offer. Such lenses would be useful with any camera.
« Last Edit: November 15, 2008, 06:39:25 PM by ErikKaffehr » Logged

Ray
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« Reply #84 on: November 15, 2008, 07:29:30 PM »
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Quote from: ErikKaffehr
Ray,

All this are good points, but I would also add that a 200/1.8 is simply much more glass, and probably expensive glass, too. In long lenses chromatic aberration is one of the major obstacles and very expensive glass, like CaF2 is used to eliminate it. Normal and short tele lenses are relatively easy to build so they often have very good performance for a reasonable price.

As far as I understand it is hard to build large aperture lenses, especially with a wide angle of view.

Best regards
Erik

Erik,
Lenses with wide apertures usually have more glass whatever the focal length, don't they? I mentioned the Canon 200/1.8 as an extreme example. It was considered by Photodo to be the finest lens they ever tested. However, the same principle applies to very expensive shorter telephotos, such as the Canon 85/1.2. Their advantage lies in the fact that such lenses produce sharp results at wide apertures. I imagine that at F1.2, that 85mm lens would not be particularly sharp. But at F2.8 it would be significantly sharper than the 50/1.4 at F2.8, but not significantly sharper than the 50/1.4 at its sharpest aperture of F8 (or F6.3 whatever).
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NashvilleMike
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« Reply #85 on: November 16, 2008, 12:48:44 AM »
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Quote from: Ray
Erik,
Lenses with wide apertures usually have more glass whatever the focal length, don't they? I mentioned the Canon 200/1.8 as an extreme example. It was considered by Photodo to be the finest lens they ever tested. However, the same principle applies to very expensive shorter telephotos, such as the Canon 85/1.2. Their advantage lies in the fact that such lenses produce sharp results at wide apertures. I imagine that at F1.2, that 85mm lens would not be particularly sharp. But at F2.8 it would be significantly sharper than the 50/1.4 at F2.8, but not significantly sharper than the 50/1.4 at its sharpest aperture of F8 (or F6.3 whatever).

You might be surprised Ray. I'm on the Nikon side of the fence so I can't speak for Canon glass in terms of their exotics, but in every test I've done with my 200/2G AFS lens, it's sharper even at F/5.6 and F/8 than any other lens I currently own (and that includes the 50), and in my opinion sharper than *any* other Nikon lens I've used in the past 30 years, and that includes any of their micro lenses, any normal 50, or any of their mid tele's. It's the one lens that I own that is limited by the resolution of the body behind it, and of course, by diffraction. As well it should be, given the cost of these things.

I do believe that when you purchase an exotic, what you are buying besides wide open performance is also a level of quality control and manufacture that exceeds that of most every other lens - being the exotics are typically built slowly and carefully, one by one, in small batches, with a lot less compromise in terms of the cost of components, so in the end it adds up to stellar optical performance.

I don't know if there are lens rental places out where you are like here in the states, but if so, try renting one for a bit and give it a go. Even if you never intend to get such a beast, they (the exotics) are eye opening in terms of what can be done in terms of lens design when cost/size/weight limitations are not present to constrain the designer.

-m
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Ray
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« Reply #86 on: November 16, 2008, 07:33:31 AM »
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Quote from: NashvilleMike
You might be surprised Ray.

Well, surprise me. I like being surprised. I can only speak from my own experience and deduce performance from the numerous MTF charts I've seen at Photodo if I don't own the lenses. I don't have the time to test every claim that seems contrary to what I'd expect. If you think I'm wrong, and you already own Nikkor lenses similar to, say, the Canon 85/1.2 and 50/1.4, then please show some 100% crop comparisons of a detailed target like a banknote or newspaper, taken at a suitable distance so all the fine detail is not revealed.

Below are the MTF charts at maximum aperture and F8, and weighted ratings at most apertures up to F8 for the Canon 85/1.2 and 50/1.4. As you can see, at F4 the 85/1.2 gets a rating of 86, compared with 84 for the 50/1.4, and at F8 gets a rating of 87, compared with 86 for the 50/1.4.

It's doubtful that such differences would mean much, even on a large print, but the performance differences at apertures from F1.2 to F2.8 probably would be quite noticeable, especially at the edges of the frame.

[attachment=9732:85mm_50m...mparison.jpg]
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ErikKaffehr
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« Reply #87 on: November 17, 2008, 01:03:06 AM »
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Hi Ray,

My point is mostly that the 200/1.8 is physically a very big lens. Aperture is something like 111, so I would expect front lens to be around 111 mm to. An 85/1.2 would have an aperture size of 71 mm. If we assume that the weight of a lens is proportional to the square of the diameter the front lens would be 2.5 times heavier on the 200/1.8 than on the 85/1.2. I also would expect the 200/1.8 to use more exotic glass.

Some lenses actually perform optimally or almost optimally at maximum aperture, but they are very few.

Best regards
Erik

Quote from: Ray
Erik,
Lenses with wide apertures usually have more glass whatever the focal length, don't they? I mentioned the Canon 200/1.8 as an extreme example. It was considered by Photodo to be the finest lens they ever tested. However, the same principle applies to very expensive shorter telephotos, such as the Canon 85/1.2. Their advantage lies in the fact that such lenses produce sharp results at wide apertures. I imagine that at F1.2, that 85mm lens would not be particularly sharp. But at F2.8 it would be significantly sharper than the 50/1.4 at F2.8, but not significantly sharper than the 50/1.4 at its sharpest aperture of F8 (or F6.3 whatever).
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jani
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« Reply #88 on: November 17, 2008, 04:08:25 AM »
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Quote from: Ray
Well, surprise me. I like being surprised.
Canon EF 200mm f/2L IS
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Jan
Ray
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« Reply #89 on: November 17, 2008, 05:35:50 PM »
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Quote from: jani

Now, that's a confused message, Jani. Are you trying to surprise me, or confirm my point?  

The images of the new 200/F2 to which you refer, are all taken at, or close to, full aperture. The lens is desirable because it can produce sharper images at wider apertures than other cheaper lenses of similar focal length, not because it can produce sharper images at apertures between F5.6 and F8 and not because it might be sharper at F2 than it is at F8. If course, the lens might also be desirable because of factors such as 'nice bokeh'.

The point has been raised in this thread that the 50D needs the finest quality glass to produce any resolution advantage over the 40D and that, in view of this fact, perhaps Dpreview should have chosen a better lens than the humble 50/1.4 to test the camera.

In my opinion, they probably could have demonstrated a slightly greater resolution difference by using a 200/1.8 at F4 (and perhaps also the new 200/F2 at F4), but would this have been a sensible comparison to make? Anyone who can afford such lenses and who wants maximum resolution for large prints would likely use another lens with a FF DSLR such as the 1Ds2/3.
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Ray
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« Reply #90 on: November 17, 2008, 05:45:27 PM »
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Quote from: ErikKaffehr
Some lenses actually perform optimally or almost optimally at maximum aperture, but they are very few.

Hi Erik,
There was at least one Canon lens tested by Photodo, which was sharpest at full aperture; the 400/2.8 non-IS version. However, although this lens is marginally sharper at F2.8 than it is at F8, it is marginally less sharp at F8 than the humble 50/1.4 at F8.
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jani
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« Reply #91 on: November 18, 2008, 03:19:18 AM »
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Quote from: Ray
Now, that's a confused message, Jani. Are you trying to surprise me, or confirm my point?  

The images of the new 200/F2 to which you refer, are all taken at, or close to, full aperture. The lens is desirable because it can produce sharper images at wider apertures than other cheaper lenses of similar focal length, not because it can produce sharper images at apertures between F5.6 and F8 and not because it might be sharper at F2 than it is at F8. If course, the lens might also be desirable because of factors such as 'nice bokeh'.
Now that you've restated your point, I see that your point was something else than what I thought it was, so, er, it was to surprise you, but evidently not.
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Jan
Rob C
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« Reply #92 on: November 18, 2008, 08:19:42 AM »
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Browsing through all of this, as I suppose one might do on a rainy afternoon in Spain, it doesn´t escape me that things were not ever so.

To those of you who are/were acquainted with the British Journal of Photography of some decade or so ago, the name of Geoffrey Crawley may be familiar. A good writer and an excellent reviewer of things photographic, his reviews on cameras and lenses were exemplary. Though a self-confessed Leica fan, particularly Leica M equipment, his reviews on Nikon were also very good and certainly reliable. He was a reviewer on whose word I bought several Nikkors without regret.

It seems to me that such writers do not write anymore, may not choose to make contributions to a digital world where reality seems to have ceased being part of many equations.

Alternatively, it might just be that the digital age has opened up a brand new hobby: theoretical photography. You know, the new skill which depends upon the discussion and intimate understanding of all factors other than the aesthetic.

It leaves me bewildered. Photography is a very simple skill which depends on four basic functions: focus; aperture; shutter speed; the additional skill of KWETG (knowing what exposure to give). Apart from those few things, the great magic of fine photograpy is in the visualisation, in the creating of an image that means something beyond I was there; I saw this; I shot it.

How we have strayed.

Rob C
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Gordon Buck
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« Reply #93 on: November 18, 2008, 09:21:47 AM »
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Quote from: Rob C
Photography is a very simple skill which depends on four basic functions: ...

Rob, I've told this little story previously on this forum but it is one that I thoroughly enjoy.  Someone once told me that a photographer needs only two things:  a camera and an audience -- and the camera is optional!


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Ray
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« Reply #94 on: November 18, 2008, 10:11:01 AM »
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Quote from: Rob C
Alternatively, it might just be that the digital age has opened up a brand new hobby: theoretical photography. You know, the new skill which depends upon the discussion and intimate understanding of all factors other than the aesthetic.

It leaves me bewildered. Photography is a very simple skill which depends on four basic functions: focus; aperture; shutter speed; the additional skill of KWETG (knowing what exposure to give). Apart from those few things, the great magic of fine photograpy is in the visualisation, in the creating of an image that means something beyond I was there; I saw this; I shot it.

How we have strayed.

Rob C

Rob,
At an elemental level, photography seems to have an appeal beyond esthetics. I remember as a very young kid being fascinated by the slowly emerging image on an exposed but initially blank piece of photographic paper in the developer dish, in the darkroom. (My father was an amateur photographer).

I never did get my own darkroom. It didn't fit in with my lifestyle and generally seemed too messy, but the idea of eventually building a darkroom remained with me for many years. When I realised one day that a digital darkroom (or lightroom) without messy chemicals was feasible and affordable, there was no stopping me.

The basic functions of focus, aperture and shutter speed remain, but the options, ease and flexibility of processing the results has increased enormously in the digital age, and remains a fascination it its own right.
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Tony Beach
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« Reply #95 on: November 18, 2008, 10:34:45 AM »
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Quote from: Rob C
Photography is a very simple skill which depends on four basic functions: focus; aperture; shutter speed; the additional skill of KWETG (knowing what exposure to give). Apart from those few things, the great magic of fine photograpy is in the visualisation, in the creating of an image that means something beyond I was there; I saw this; I shot it.

I don't think the basic skills can be separated from the visualization.  Once learned, the basic skills can only be mastered when they become integral to the photographer's vision.

Quote
How we have strayed.

Very true and very regrettable.  I stopped taking this thread seriously a long time ago, but I peek in as it grows and grows, and I found your post to be a pearl shining in the mud.  I probably should find the forum on this website (or somewhere else) where more elevated discussions are engaged in and get away from these gear fixation discussions.
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