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Author Topic: Optical corrected vs Digital corrected  (Read 1384 times)
opgr
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« on: August 09, 2012, 01:54:04 AM »
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So, which would you prefer:

- an optically corrected lens with many compromises in ALL optical qualities,

or

- a moderately distorted lens with SOME exceptional optical qualities and auto-digital corrections in post

Bonus points:
Which optical qualities would you like corrected at what stage?


For example:

For normal and telelens, I would personally have little problem with a plane distorted lens, as long as it has perfectly consistent colorbalance and exquisite OOF drawing. If it is a wide angle, I would prefer it to be sharp, but I have found that I don't mind chromatic aberrations so much, ever since being able to correct those automatically in post.

From what little I have seen of the RX100 RAW files, it is a slightly barrel distorted lens, with slight chromatic aberration, but it seems to produce pretty good "drawing". So, perhaps the engineers have chosen to keep some of the distortions which can easily be mitigated digitally, in favor of other optical qualities and cost?
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Regards,
Oscar Rysdyk
theimagingfactory
BernardLanguillier
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« Reply #1 on: August 09, 2012, 01:59:18 AM »
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From what little I have seen of the RX100 RAW files, it is a slightly barrel distorted lens, with slight chromatic aberration, but it seems to produce pretty good "drawing". So, perhaps the engineers have chosen to keep some of the distortions which can easily be mitigated digitally, in favor of other optical qualities and cost?

I would personally call the distortion on the wide end very heavy, but I agree with you that they have probably come up with a good compromise considering the software tools available today.

Cheers,
Bernard
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A few images online here!
opgr
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« Reply #2 on: August 09, 2012, 02:05:02 AM »
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As another example:

I don't mind the diameter of a lens as much as I mind the sometimes obtrusive length. So I would love to have a Canon 24-70, mk1, but slightly more compact in length IF that could be achieved using digital plane corrections, but otherwise keep its excellent drawing on the teleside.  
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Oscar Rysdyk
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torger
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« Reply #3 on: August 09, 2012, 03:58:01 AM »
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For compact cameras I think the proper design is to rely quite much on digital correction, especially concerning barrel distortion, that way you can make zoom lenses with fewer lens elements and thus make them more compact (and cheaper). This is also what we see on most of the new compacts.

For "high end" photography (pro DSLRs, medium format tech cams etc) I prefer good optical correction, since the less you need to correct in post-processing the higher quality the result tends to be. I also use third party raw converters without lens profiles so it becomes easier for me if the unprocessed raw has high quality. I use a tech camera system and those lenses have the design possibilities that no large aperture is needed (less correction needed) and there is no mirror box (shorter flange distance, simpler wide angle designs) which leads to very high optical performance for their specific use case without needing very complex optical designs. The exception is Rodenstock wide angles which are retrofocus designs and therefore rather complex.
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BartvanderWolf
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« Reply #4 on: August 09, 2012, 04:13:23 AM »
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For "high end" photography (pro DSLRs, medium format tech cams etc) I prefer good optical correction, since the less you need to correct in post-processing the higher quality the result tends to be.

Hi,

I agree. Complex optical corrections are also complex post-processing corrections. Some of them are better solved in the optical domain, such as OOF rendering or glare. An analogy would be the effect of a polarizer filter, only achievable when dealing with the actual light itself.

Postprocessing also tends to increase noise and potentially lose a bit of resolution, depending on the specific processing required.

Cheers,
Bart
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hjulenissen
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« Reply #5 on: August 09, 2012, 06:34:05 AM »
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Hi,

I agree. Complex optical corrections are also complex post-processing corrections. Some of them are better solved in the optical domain, such as OOF rendering or glare. An analogy would be the effect of a polarizer filter, only achievable when dealing with the actual light itself.

Postprocessing also tends to increase noise and potentially lose a bit of resolution, depending on the specific processing required.

Cheers,
Bart
An ideal joint design (optics + dsp) would be able to do "global" optimizations that may not be possible of each component is to be optimized in isolation.

I imagine that designing a lense is all about compromises. How large can we go? How expensive? How much CA? How much vignetting? etc. If any one of those requirements can be relaxed by correcting digitally instead, it might mean that other requirements can be more stringent. E.g. more lense resolution traded for more barrel distortion corrected in dsp. The end-result should then be better "total quality" (or lower cost, lower weight, etc).

-h
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