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05-02-2009, 01:32 AM   #16
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A new version with more consistent AF performance would be welcome.

I would like that clinical sharpness of fa limited quality too

05-02-2009, 09:35 AM   #17
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An old man's take on wide angle zooms.

QuoteOriginally posted by roentarre Quote
A new version with more consistent AF performance would be welcome.

I would like that clinical sharpness of fa limited quality too
I am in no way disappointed with the image quality or he focusing ability of my DA* 16-50 f/2.8 lens. I am of a certain age, and have used lenses for a long time now. I know that the following things work against the ability of the lens designer

Short Focal Length
. As the lens gets wider, more compromises must be made to move the back focus out to the film/sensor plane.

The lens must project an image for almost three times its focal length to make it sharp on the sensor/film. So, the lens designer must, in addition to the wide field of view, add a projection lens at the back so the image does not focus way out in front of the sensor or film. This is true of both zoom and prime wide angle lenses.

This is also why Pentax and Nikon and many other normal lenses from early days were 55mm lenses, not the 43mm that is technically the normal focal length. It has everything to do with the back focus distance from mount to film and not much to do with normal fields of view. At 55mm the lens did not need a projection set of elements added.

Fast aperture. As the aperture gets wider, the lens elements must also be made wider. The larger the lens element, the more difficult it is to design and manufacturer.

This is also one of the reasons Chromatic Aberrations are more common in fast (wide aperture) lenses because as the lens element gets larger, getting all the colours of the spectrum to focus at exactly the same point gets very difficult. The further from the centre of the element, the more difficult the problem. Chromatic Aberration is simply the difference in focusing point from the various colours of the spectrum. The lens is acting like a prism. As one stops down, CA decreases simply because you are blocking off the edges where the worst angles are found.

Variable focal length
. If one thinks about the difficulties involved in creating a multi- or vari-focal lens, the mind boggles. The art of compromise gets stretched to its limits. The larger the range, the more difficult the designer's problem.

You may have noticed that I have no zoom lenses much wider than 3:1. That is simply because I am too picky about my images to use a super zoom, despite my longings to be able to do everything with a single lens. (I, too, have LBA to the max.) Obviously, I have no objections to zooms, provided the image quality is adequate. The only crappy zoom I have is the 28-80. It was bought to go with an ME in my wife's backpack for a cycling trip around western Europe. Light and flexible was the goal with no intent of large prints.

Please note that the widest lens in my arsenal is the DA 12-24, and its ratio is only 2:1. Think of the Sigma 10-20, the Nikon 14-24 and 12-24 and everyone else's really super wide lenses. The ratios are very small for the reason that building a lens at these short focal lengths is enough of a problem, let alone handling extreme zoom ratios.

One solution is to ignore the distortions and create the Pentax 10-17 fisheye. This is much easier to design and manufacture than the 12-24.
05-02-2009, 10:07 AM   #18
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Thanks Albert, I knew they were hard to make, just not why. One of my favorite lenses is my FA 20mm F2.8. It's a stellar lens, but I had always wondered why it was "only" F2.8 instead of F2.0 or even wider. Now I know. As it is, it was 'almost' too expensive at F2.8 any faster and it would have been out of wallet range.

NaCl(it's easier to have LBA if you have deep pockets)H2O
05-02-2009, 10:30 AM   #19
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QuoteOriginally posted by NaClH2O Quote
Thanks Albert, I knew they were hard to make, just not why. One of my favorite lenses is my FA 20mm F2.8. It's a stellar lens, but I had always wondered why it was "only" F2.8 instead of F2.0 or even wider. Now I know. As it is, it was 'almost' too expensive at F2.8 any faster and it would have been out of wallet range.

NaCl(it's easier to have LBA if you have deep pockets)H2O
That sig line is so accurate it is frightening. That 20 is a great lens. I've known one other person who has it, and LBA hit hard. I'm avoiding it on the grounds I have the 16-50/2.8 that covers the focal length. I decline to have a look at any 16-50 at 20mm vs FA20 comparisons. I cannot afford any more lenses right now.

09-11-2009, 02:31 PM   #20
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QuoteOriginally posted by Canada_Rockies Quote
The decenter claims are based on corners that are not equally sharp (or unsharp). The top right is softer than top left or vice versa.

For those who want a perfect lens, just add DxO Standard to your lens. It's magic. They let you download and try for free. Caveat - slower than molasses in January. Book a nice lunch at the Ritz when you let it loose. You don't have to watch.
How does this program create areas of sharpness from areas of softness caused by a lens defect? This is the only way that it could make it a perfect lens. Adding USM or whatever method to a soft area usually does not work very well.

Maybe you meant that it corrects for CA, distortion, and vignetting. This is nice of course.
09-12-2009, 08:34 AM   #21
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QuoteOriginally posted by Canada_Rockies Quote
See Eric's reply above. It also takes care of vignetting and the exposure fall off toward the edges and corners. Basically, it analyzes the image and its EXIF data and applies the measurements learned over testing the exact combination of lens and body. It can even correct the "mustache" distortion that lens designers use to get as close to a straight line at the edges as they can. As I said, it's magic. And slow.
I have not tried this yet because DxO only supports 8 or so lenses for the pentax cameras. How useful is this software for unsupported lenses?
09-12-2009, 10:29 AM   #22
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QuoteOriginally posted by apisto Quote
I have not tried this yet because DxO only supports 8 or so lenses for the pentax cameras. How useful is this software for unsupported lenses?
Even with unsupported lenses, it makes sensor based adjustments, but I don't find them as helpful as the results with my three DA lenses that are supported. For non DA lenses, I don't bother with DxO.
09-12-2009, 12:28 PM   #23
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QuoteOriginally posted by Canada_Rockies Quote
Even with unsupported lenses, it makes sensor based adjustments, but I don't find them as helpful as the results with my three DA lenses that are supported. For non DA lenses, I don't bother with DxO.
Me, I run everything through DxO and the only supported lens I have is the DA*16-50. The only one I use frequently, that is.

09-12-2009, 02:42 PM   #24
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QuoteOriginally posted by Bart Quote
Me, I run everything through DxO and the only supported lens I have is the DA*16-50. The only one I use frequently, that is.
So I would just run all of the dng's out of the camera through DxO and then import them into LR, right?
09-12-2009, 04:36 PM   #25
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QuoteOriginally posted by apisto Quote
So I would just run all of the dng's out of the camera through DxO and then import them into LR, right?
That's the way I do it. I don't find too much advantage running my M's through DxO, but the DA's really turn out nicely. Slow, but I don't have to be there to follow it.
09-13-2009, 02:09 AM   #26
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QuoteOriginally posted by apisto Quote
So I would just run all of the dng's out of the camera through DxO and then import them into LR, right?
I use PEF. I'm not exactly sure if DxO reads DNG. They can use it as an output format for sure.
Also, I don't import the output into LR but into MS Expression Media.
But why don't you download a test from DxO? You get something like 3 weeks to experiment and compare the output with the results from other RAW converters.
See what you like best.
I compared with Bibble, Silkypix and LR.
09-13-2009, 05:03 AM   #27
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QuoteOriginally posted by Bart Quote
I use PEF. I'm not exactly sure if DxO reads DNG. They can use it as an output format for sure.
Also, I don't import the output into LR but into MS Expression Media.
But why don't you download a test from DxO? You get something like 3 weeks to experiment and compare the output with the results from other RAW converters.
See what you like best.
I compared with Bibble, Silkypix and LR.
I own and use LR. I am new to all of this, but I am already finding that while I love taking pictures, I really do not like post processing pictures, although I do it when needed. And it often is needed on my pictures. I am hoping something like DxO will be more of a fire and forget solution and then LR will be mostly just for organization. (Expensive just for that purpose, but I already bought it. Oh well.)

I do plan on using the trials, but not till winter starts coming on and I have more time to sit in front of the computer, so I have enough time to actually use the programs during the trial.

EDIT: I have read around on DxO's website and one thing is not clear to me. Do all modules output RAW files? It sounds like some, such as the lighting module only output JPG or TIFF.

Last edited by apisto; 09-13-2009 at 06:23 AM.
09-13-2009, 06:18 AM   #28
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From the manual:

In the left-hand area of the top section is where you can specify what output file formats you would like created during the processing phase of Optics Pro. Optics Pro supports three output formats: JPEG, TIFF, and DNG. (DNG formatted files can only be created from RAW input files.)
09-13-2009, 07:25 AM   #29
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Got one in February. No problems at all.
09-14-2009, 05:51 AM   #30
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QuoteOriginally posted by Bart Quote
From the manual:

In the left-hand area of the top section is where you can specify what output file formats you would like created during the processing phase of Optics Pro. Optics Pro supports three output formats: JPEG, TIFF, and DNG. (DNG formatted files can only be created from RAW input files.)
Thanks, Bart. I will quit dragging the thread off topic now.
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