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Cheap optics and makeovers

Cheap cameras has cheap optics. A typical case in point is the Minolta Z10. This is a 8x “superzom” that comes complete with a bad case of pincussion distortion and a generous amount of chromatic aberration (CA, aka. purple fringing). In other words, this camera has a less than ideal lens.

The good news is that this type of optical defects can be fixed. Panorama Tools (free) with PTlens (also free) corrects pincussion distortion in a few seconds, and the colour replacement tool in Adobe Photoshop CS (not free) paints over purple fringing like magic. There is also a specialized software package, DxO Optics Pro (not free) that is supposed to automatically fix the following optical defects: blur, distortion, CA and vignetting, based on precise mathematical modelling of the camera and the lens. So - if you feel like it, you can save yourself a few bob by buying a camera with a cheap lens, and fix up the images afterwards.

Not all optical defects can be fixed by post-processing, but radial distortion and CA can.

I can't afford the DxO Optics Pro, but I'm familiar with Photoshop and Panorama Tools. To demonstrate how optical defects of a cheap lens can be corrected, I've created a demonstation with "before" and "after" images. The image below is a JPEG straight out of the Minolta Z10. Move your mouse over the image to see how it looks after I've corrected the distortions and the CA (requires JavaScript enabled).

makeover

When you've got the defects of your particular lens pinned down, you should be able to automate these operations as a Photoshop action - so doing these corrections doesn't need to take much time.

This opens up for some intertesting possibilities. Instead of having very complex and expensive high presicion optics, lenses could be made simpler and to looser standards. The manufacturer could then profile each lens, and embed the profle in the lens. The lens should then pass its profile on to the image file (like EXIF), and any software processing the image (in or out of camera) should be able to use the embedded profile to automatically correct for all the profiled optical defects.

Why do this? I believe that using software fix optical defects is several mangnitudes cheaper than manufacturing "perfect" optical hardware. Such "self-correcting" lenses should be cheap, lightwight and fast. Wow!

3 responses:

Hello, fellow shooters!

I want to question the notion that software correction should supplant high quality optics in order to allow for lower standards in lenses.

This because any lowering of standards means a slippery slope and a highly undesirable regression towards the mean - and a rather dissatisfying mean - as is the case whenever we cut corners. A lowering of standards is what we see in consumer grade lenses for SLR cameras, and if one truly cares about the difference between the merely good and the brilliant such lenses are not recommendable as they are manifestly incapable of delivering suffient detail or color rendition if you want something more than that which is "good enough" for the average family shooter who has not (yet) developed the desire for something better. If the manufacturers perceive that "the average customer" does not want, need or demand high standards the result will be a general lowering of performance which cannot be corrected by any kind of software correction wizardry. If standards for a number of relevant parameters of quality become less exacting, it is therefore the consumer who must suffer, and it is very possible that the price of high quality versions would rise accordingly. That is hardly to our advantage. Yes, it might seem alluring to have brilliant optics for a modest sum of $$, but the world is not so simple, and free lunches are rather rare. The most expensive tool you can buy, is the one you become dissatisfied with and have to buy anew.

Most of the above holds true for optics in all types of digital cameras, but I think it may safely be suggested that a main problem with compact models in particular is the manufacturers' tendency to make zooms with a focal length range that is way too broad to yield optimum results at any single focal length.

It may be unwise to accept low standards just because the price is lower. Personally I would rather save for one year or more to get a good lens instead of buying a consumer grade one now - which is precisely what I just did. It also merits mention in this context that if we are talking about interchangeable lenses for SLR cameras like the Nikon D series, high quality at a pleasant price point is obtainable if one chooses prime lenses rather than zooms.

Take a look at the four-thirds system from Olympus, Kodak, Fujifilm et al! While it doesn't come with cheap lenses, it has a provision where the optical characteristics specifc to a particular lens is transferred to the camera. The camera can then use this information to correct lens defects such as vignetting and barrel distortion. The same lens profile can also be saved with the image files for automatic post-processing.

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Hi! I had a lot of talk with users of different image-producing equipment. It doesn't matter if it's an adaptive mirror telescope, radio-telescope, optical microscope, high resolution REM or TEM or our retired photographers favourite: Canon A-1. Nothing can beat good design in image acquisition. Information which is not there, can not be recalculated. Misinformation (noise of CCD chips for example)is always bad. So I like this high end stuff here at Max-Planck. But it always depends on the task. If you want to maximize the result for your money, you have to find a good balance of spending money on your equipment. Especialy since one sometimes tend to over-engineer something. Is an original Leica lens really a good investment? We opted for Canon instead using Canon real Macro lenses with 12 ASA black and white films.

Back to the thread: the lens-designer can only plan for problems which can be corrected (some can't be corrected: flare for example) and I would like this corrections instantly on display. I like 'what you see, is what you get' otherwise I won't shoot. I fear there is no solution to this somewhat philosophical problem. I really envy some people who do not see the difference and on other days I'm happy that I see the diference.

- Greetings from Germany, Achim (Canon A-1 and Dimage Z10 owner)

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