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Old Jun 25, 2012, 7:31 AM   #1
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Default big zoom lens = degraded image quality ???

It seems like all the camera companies today are in a race to see who can produce the biggest zoom lens on their so called super zoom bridge cameras. Question: As the zoom power goes up, does the image quality start to go down ??? In other words, if all things are equal, will a 21X zoom lens camera produce better image quality than a camera with a 42X zoom lens ??? It seems logical to me that at some point image quality will be degraded as a result of all the extra glass required in these big zoom lenses and the magnification of camera shake. Your opinions please.
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Old Jun 25, 2012, 8:56 AM   #2
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To an extent, you're right. A lens that does a lot of things won't do any of them very well.

But lenses for smaller image sensors are easier to make, and therefore easier to make well, than lenses for larger image sensors ('Full Frame', APS-C, 4/3, etc.). (A 15X Tamron 18-270mm lens for an APS-C sensor costs $550, which can buy two 16X Panasonic ZS15 digital cameras.)

So, the key point you acknowledge but gloss over is that all things aren't equal.
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Old Jun 25, 2012, 9:54 AM   #3
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A lot depends on how much effort the manufacturer has put into the the design of the lens, which is reflected in the price.

The camera software is also starting to correct some of the distortions and aberrations before the image is saved. For example my DSLR corrects purple fringing automatically. There is computer software available to correct lens distortions so one could see this function incorporated in the camera software as processing power in the camera augments.
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Old Jun 25, 2012, 9:57 AM   #4
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Quote:
Originally Posted by Bob Nichol View Post
A lot depends on how much effort the manufacturer has put into the the design of the lens, which is reflected in the price.

The camera software is also starting to correct some of the distortions and aberrations before the image is saved. For example my DSLR corrects purple fringing automatically. There is computer software available to correct lens distortions so one could see this function incorporated in the camera software as processing power in the camera augments.
True, but that stuff generally doesn't show up in the "bridge" cameras surplusshooter is referring to.
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Old Jun 25, 2012, 10:03 AM   #5
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Quote:
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True, but that stuff generally doesn't show up in the "bridge" cameras surplusshooter is referring to.
It may become more common as the the cost of processor and firmware drops according to Moore's Law.
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Old Jun 25, 2012, 11:22 AM   #6
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Simple answer is - YES, as the focal length and range of zoom increase, the image quality degrades.

But, you also have to realize all manufacturers segment the market. Not every "bridge" camera is a superzoom. Superzoom cameras are created for a specific market segment. For example, a friend at work bought a superzoom because her daughter was on a swim team. My co-worker doesn't have access to the pool deck so she has to shoot from far away. Being able to tightly frame the shot from the distance produces better shots than heavily cropped shots from a digicam with shorter focal length but having to heavily crop the images. Similarly for budding wildlife photographers that don't want a DSLR and don't have the patience to get close. The photos from the longer focal length camera are better than a heavily cropped image from a camera with shorter focal length but better lens. But for those people who want better IQ in a bridge camera, they'll forsake the superzooms and go with shorter zoom range but better IQ. There really is a market for both types of camera.
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Old Jun 25, 2012, 12:38 PM   #7
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I think all else being equal (which is rare..!),the shorter focal length lens should have better optical quality. Also,in the case of a bridge camera,the shorter lenses tend to have slightly faster apertures at the long end- giving you the option for a faster shutter speed or a lower iso setting (all else being equal).
Image stabilisers generally seem to be more effective at shorter focal lengths also- for obvious reasons. Autofocus performance also seems to be superior in the shorter lenses (used at the long end) than their eagle eyed cousins.
My guess is,in the case of a bridge/superzoom,at this moment in time- there is an "optimum" focal length relative to all round IQ and performance- but much of that depends on the camera it's stuck to,with many variables to consider.
Would Panasonic's FZ-150 be as good with a Sony HX200v lens attached.... maybe it would be better...?? Or would the Sony be better (or worse) with the Panny' glass attached...??
Very difficult to know for sure....!
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Old Jun 26, 2012, 12:25 PM   #8
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Thanks everyone for all the replies to my question. After reading all of the replies, it appears that the general consensus is that as the focal length/zoom power increases, the overall image quality decreases. "SIMON40" brought up a good point and it's really something to ponder with his comment about "optimum" focal length/zoom power relative to all around image quality and performance. This makes you wonder, "what IS the "optimum" optical zoom power ? Is it 6X, 10X, 18X, 21X, 26X, 36X, 42X ? It seems logical to me that they ALL can't be 100% equal relative to overall image quality. Anyone want to make a guess as to what the "optimum" zoom power would be for the best overall image quality ? I am talking about the latest fixed lens super zoom cameras, not DSLR's. Thanks, and I can't wait to hear your opinions. My guess would be somewhere around 20X or less.
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Old Jun 26, 2012, 1:39 PM   #9
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surplusshooter - you're confusing focal length and zoom ratio. What Simon was referring to is the fact that a particular zoom lens tends to have a "sweet spot" where it performs the best. So, it's not that a particular zoom-ration (10x, 12x, 20x) offers the best IQ. It's that for a given lens, the sweet spot is usually a particular focal length WITHIN that lens' total zoom capability.

For what it's worth, I think you're a bit too hopeful that the IQ of a 20x zoom digicam is going to be as good as a 3 or 4x zoom of similar quality.

You're also ignoring the fact that zoom ratio is the sole determining factor. Every one of these cameras has processing involved. You're never going to arrive at a golden answer of: ##x zoom cameras produce the best IQ. You really have to take every camera on an individual basis. Focus performance, white balance performance, jpeg processing (or raw capability), high iso performance are just some of a myriad of variables that affect image quality. With so many camera models out there and new ones coming out every year, it's impossible to come up with any reasonable "buy ##x zoom camera to get the best pictures" rule of thumb.
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Old Jun 26, 2012, 2:26 PM   #10
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Part of the difficulty in these kinds of discussion is that focal length and zoom ratio are not the same thing, as the sensor size is a contributing factor. You can have two cameras with the same zoom ratio (and even with the same 35mm equivalent focal lengths), but with different actual focal lengths.
Sensor size and the optical quality of the lens are the controlling factors in IQ, not the zoom ratio.

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