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Old Jun 4, 2007, 8:50 PM   #11
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TCav-

Here isa photo sample from the Sigma 18-125mm lens (mentioned earlier in this thread)that I purchased on E-Bay for $140. The lens was mounted on my Canon XTi. It is a good example of what a low cost lens can do. Bounce flash was used. As long as we provide a good light source, these low cost lenses are capable of pleasing results.

The bounce flash used in this photo sample is much more pleasing than the direct on camera flash photo sample posted earlier in the thread.

Sarah

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Old Jun 5, 2007, 5:36 AM   #12
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Sarah -

I'm not saying, nor have I ever said that the 18-135 isn't a good lens. What I have said, and will continue to say,is that the Tamron 18-200 isn't as good a lens as some less expensive, more moderate zooms (like, perhaps, the 18-135), and that all indications are that the Sigma isn't any better. The Nikon, however, seems to be better than both, though I can't say by how much.

Here's a test pattern I made for testing my lenses. The resolution is greatly reduced so that I can post it here. The original is in Microsoft Visio 2003 and printed on HP Premium Plus Glossy Photo Paper at the highest resolution of my HP CP1160.
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Old Jun 5, 2007, 6:02 AM   #13
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This is a crop of a photo of the test pattern using the Minolta 18-200 at f/8 at 105mm (middle of the range, stopped down):
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Old Jun 5, 2007, 6:03 AM   #14
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This is a crop from a similar shot using the Minolta 28-105, also at f/8 at 105mm:
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Old Jun 5, 2007, 6:05 AM   #15
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And finally, this is a crop from a similar shot using the Minolta 70-210 ("Beercan"), also at f/8 at 105mm
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Old Jun 5, 2007, 6:07 AM   #16
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I beleive it's pretty clear that the more moderate zooms are far sharper, and have far less CA than the super zoom.
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Old Jun 5, 2007, 8:58 AM   #17
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TCav-

I am in total agreement. That is why the Sigma 18-125mm exceeds/betters the Sigma 18-200mm and the Tamron 18-200mm lenses, and any of the dimmer lenses that need either outdoor light or an external flash to produce good results.

However, if you know their deficiencies and create work arounds, thery can create pleasing, but not stellarresults.

Sarah
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Old Jun 5, 2007, 12:23 PM   #18
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Sarah and TCav,

I've found your discussion regarding zoom lenses to be quite interesting and enlightening - thank you for that! Being a superzoom camera user (Fuji S6000fd) I am curious as to how these types of lenses compare. More specifically, the Leica lens that the Panasonic FZ50 uses is lauded for its sharpness, lack of CA, and speed - Ibelieve it is F2.8-3.7.How does this Leica lens compare with a DSLR lens of comparable coverage? How is the Leica lens able to be so fast, yet I often see DSLR zoom lenses with a range of F3.5 to 6.3?

Any thoughts would be greatly appreciated!
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Old Jun 5, 2007, 12:46 PM   #19
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flippedgazelle wrote:
Quote:
Sarah and TCav,

I've found your discussion regarding zoom lenses to be quite interesting and enlightening - thank you for that! Being a superzoom camera user (Fuji S6000fd) I am curious as to how these types of lenses compare. More specifically, the Leica lens that the Panasonic FZ50 uses is lauded for its sharpness, lack of CA, and speed - Ibelieve it is F2.8-3.7.How does this Leica lens compare with a DSLR lens of comparable coverage? How is the Leica lens able to be so fast, yet I often see DSLR zoom lenses with a range of F3.5 to 6.3?

Any thoughts would be greatly appreciated!
The comparable coverage of an Ultrazoom is achieved because of the higher crop factor due to the much smaller image sensor used in Superzoom cameras. The actual focal length of a superzoom lens is much smaller than it's apparent or effectivefocal range. Therefore you would have to compare the lens on the FZ30 to a much smaller 35mm lens equivalent and not the 35mm-to-420mm effective range they quote in the specs. If that wasreally35mm-to-420mm lens and they could make itF2.8-3.7,would cost you thousands of dollars even if it wasn't stamped Leica.

I'm not 100 percent sure but I believe the crop factor of the FZ30 is 4.83X so the actual focal length of the FZ30 is about 7.2-87MM.

The same concept holds true on most digital SLRs. The focal lenghts of a 100mm lens when used on my DSLR changes by a crop factor of 1.5 and effectively acts like a 150mm lens because my image sensor is smaller than a 35mm film negative.
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Old Jun 5, 2007, 1:46 PM   #20
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flippedgazelle and meanstreak-

Have opened a whole new element to our discussion. It will allow us to discuss lens design parameters. Meanstreak has voiced it rather accurately. When the lens designer is at square one, is one natural preliminary question will also be what is the size of the camera's imager. That question is very important because that affects the size, aperture, sharpness, a a whole host of other details the we will find in the finished/manufactured lens.

We are constantly have to deal with three imager sizes currently.

(1) The Full Frame image is exactly what it proclaims, a full frame 35mm sized (24mm X 36mm size) imager.

(2) The cropped imagers found especially on consumer level DSLR cameras like the Nikon D-40, the Nikon D-40X, the Sony A-100, the Olympus E-300, E-330, E-500, E-400, E-410, the E-510 the Pentax K100, the Pentax K-10, the Canon XT, the Canon XTi, the KM-5D and the KM-7D and a host of other DSLR consumer level DSLR cameras. They all use an imager that is roughly 15mm X 23mm. There are three major manufacturers of CMOS imagers of this type, Kodak/Panasonic (who have the samllest 13mm X 17mm 4/3 imager), Sony, and Canon. They very slightly in physical size. But the major issue is that these imagers are substantially smaller in size that the Full Frame imagers. It is because of this large difference in size of the imager, that we speak of the "crop factor" to be applied to this type of DSLR crop cameras

(3) The imagers used on point and shoot and super zoom digital cameras where the actual imager is a much, much smaller design, call the CCD that is roughly about only 15% of the size of even the cropped CMOS imagers.

Jumping back to flipped gazelle's question, about the Leica branded, though Pansonic produced lenses used on the Panasonic FZ-30 and FZ-50 cameras. The first thing that you will notice when looking at the lens installed on a FZ-30 or FZ-50 camera (and that was also mentioned in meanstreak's post) is that the actual physical size of the lens is much smaller than even a lens designed for a cropped imager based DSLR.
cameras.

When the lens is physically smaller, the lens designer is faced with many fewer problems in manufacturing and design parameters. In short it is much simpler to design and cheaper to manufacture.

The next series of lenses that we find are the 4/3 lenses such as the lenses used on the Olympus and Panasonic DSLR camera. These lenses are still smaller the Canon EF, the Nikon DX or Sigma DC lenses because the Olympus and Panasonic DSLR cameras use the smallest (13mm X 17mm) CMOS imagers. The Olympus Zukio series of lenses are an example of this smallest series of DSLR lens just because of the small (13mm X17mm) imager being used.

The next physically larger series of lenses are the Canon EF, Nikon/Nikkor DX, and Simgma DC (plus others) lenses that are designed for the somewhat larger Canon and Nikon CMOS imagers which are more or less 15mm X 23mm in size.

Lastly and yet even larger in size are the lenses designed for the Full Frame (24mm X 36mm) sized CMOS imagers.

The larger the physical dimensions of the lens, the more complex the design, refinement, and manufacturing processes are going to be. Because of that you cannot realisticaly or theoretically draw a direct comparison between the lens used on a superzoom digicam with the Lens used on 4/3's DSLR's, crop imager based DSLR cameras, or Full Frame DSLR cameras. They are just a great deal different in design, manufacture, and implementation.

Hopefully, I have not muddled this too much. However, it is an interesting area to delve into for this thread.

Sarah
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