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Old Dec 20, 2003, 5:48 PM   #1
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Default lens quality vs imager resolution


I have been doing some experimenting with my new Fuji Finepix 2650- a basic 2.1 mpx camera with a 3x zoom lens. Using both a test pattern and general pictures, I can't see any difference in image quality between 1600x1200 and 1280x960 settings. In fact I have to go down to 800x600 before I can see any difference.

Very roughly, the Fuji lens seems to be generating 10-20 lines per mm of resulution at the focal plane. In my 35 mm photography days, I recall that a good fixed focus lens would go up to 80 lines/mm resolution. So, the Fuji lens seems rather poor by comparison.

So, is my assumption correct that the lens quality is limiting resolution? If so, is that generally true of the "point and shoot" cameras and their lenses? Or does the Fuji have a poor quality lens for its type.

If this is generally true for point and shoot cameras, why would you ever want more than 2.1 mpx imager resolution for normal picture taking.

But there are plenty of 4 mpx point and shoot cameras out there. Do they have significantly better lenses to take advantage of the increased imager resolution?
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Old Dec 20, 2003, 6:21 PM   #2
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I think that if you could have to identical cameras, the only difference being the sensor resolution (say 2 vs 3 megapixels), the higher megapixel camera should (in theory) produce a better image just because there is more data to work with in creating the image.
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Old Dec 21, 2003, 1:14 AM   #3
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Hi- I am wondering how you are comparing these images. Is it via prints or by looking at your computer monitor or by the LCD on the camera? Mike
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Old Dec 21, 2003, 2:25 AM   #4
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jdmarchand......It wouldn't surprise me if the quality of lens and ccd were optimal. To turn your argument around from a manufacturing point of view: Why put in a much better lens than the sensor can do, or, what size prints are the buyers of my consumer cam expecting and what is the lens quality limit required?

Increasing the sensor pixel density doesn't just give resolution improvement - other benefits like sensitivity, noise reduction and better JPEG encoding come as well. But since Mpixels are the simple yardstick used by buyers to distinguish between cameras and the price paid, I'll bet very few actually print 6x4's from a 2 and 4 Mpix cam and see resolution improvement! It's the badge on the front of the camera that matters. VOX
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Old Dec 21, 2003, 4:56 AM   #5
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Default Re: lens quality vs imager resolution

Originally Posted by jdmarchand
I can't see any difference in image quality between 1600x1200 and 1280x960 settings. In fact I have to go down to 800x600 before I can see any difference.
There are other variables to consider as well as pixel size on the sensor and lens quality, before you can compare like with like. Two of these are.....

1. Compression applied to the image.

Are you comparing jpegs with each other? If you start with a different pixel-sized image you'll get a different result, but they may look identical when viewed at a particular size. Inspect the same scene taken on a tripod or other firm support, at different settings, and view the images alongside each other in your image editor at a vastly magnified size that shows the individual pixels. Only then will you see the differences.

[I use 'economy' jpeg mode routinely in my camera, rather than 'fine', because I know I can't see the difference on a pixel by pixel basis. However, I'm aware that if I want to do a lot of twiddling and resaving, I'm storing up problems , which will degrade the image later.]

2. Software sharpening applied in the camera, maybe without you knowing it's there.

This is often ignored in this forum and in camera reviews. Many consumer digicams produce stunning results compared with more expensive cameras WHEN one uses their default settings. If lots of software sharpening is applied before the image is even saved in the camera, it may well look wonderful, even if it's got very few pixels, *provided* it's viewed at the 'right' size. Once you start twiddling, e.g., for enlargements, you may prefer to start with an unsharpened image and sharpen as the last thing before printing.

So inspect the images side by side and pixel by pixel to see the differences, and then condemn the lens if they're identical!
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Old Dec 21, 2003, 9:33 PM   #6
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Using the resolutino chart from imaging-resource.com from the 2650, the resolution is avreage for 2mp cameras, at approx. 1000 lines per/picture height. Reducing the pixel dimensions as yolu specfied, a reduction in resolvement was evident, as expected. In light of this, I would have to question your specific methodology that resulted in your conclusion. If that is valid, then perhaps your specific test sample is defective, though this would seem unlikely.

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Old Dec 22, 2003, 4:16 AM   #7
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........2. Software sharpening applied in the camera, maybe without you knowing it's there..............

Yes that's a very important point.

Most current prosumer digital cameras produce native soft pictures!!

Does this surprise you jd? It's caused by the need to include an optical filter in the lens system to reduce digital aliasing, by restricting optical resolution.

I agree this is not talked about much. But it works like this: take a really cracking lens put it in front of a sensor, digitally sample the output from the sensor and the high resolution detail from the lens will interfere with the sampled image data. You can often see the aliasing effect on resolution charts- even after filtering. Nyquist has something to say about this. Optical filtering is great for JPEG compression. The softer you make the pics before compression, the easier it is to compress them and the smaller are the files.

So really good lenses are no good on current digital cameras! The problem is the camera/sensor sampling rates need to be increased to make more use of the optical bandwidth the lens is providing. That means faster in camera processors, better ccd's and probably more power.

Yes, you might have the Megapix, but is your camera sampling them fast enough to translate this into effective resolution gain at the image file? No manufacturer as far as I know sells a prosumer digital camera on its optical resolution spec - that would start some talking if they did!

So, in your tests, turn off sharpening (by setting to soft) and you will see and compare like for like what the camera is really producing at each resolution setting, Nothing is simple I'm afraid. VOX
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