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08-18-2011, 08:45 AM   #1
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Problems with Haloing (or is it?)

Hey guys,

So I bought some months ago an old 50mm/2.8 film lens. It was pretty cheap and it does a good job except for one thing: Haloing (or is it the right word) is pretty disturbing and makes the processing quite hard, especially when it comes to accentuate contrasts and clarity, or else create a more unreal, HDR-like kind of effect.
I don't know where this comes from, maybe something inside the lens is broken (it actually does make a ticking noise when I shake it in my hands, but well, I thought that'd just come from the manual aperture thing in the lens( a word I should learn)).

Here are some concrete examples:

Here is a comparison of what the basic Jpg image gave me and the kind of black and white highly contrasted pic I wanted. The chin is quite disturbingly irregular, even on the actual 'regular' picture, and you can see this kind of white ugly halo on the contours on the BW version...quite annoying.





Another problem comes when I want to modify the colours and use the fill light and strenghthen the 'blacks' for a kind of HDR-like picture:



Here is a zoom of the upper part



And a detail on the down part:






So my questions would be: do you know where the problem comes from? Is it a problem often encountered with film lenses, which means will I have this problem if I buy other film lenses?
Also: would you know easy way to correct this, either on CS3 or Lightroom (or anything I can easily and hopefully freely download)?

08-18-2011, 09:35 AM   #2
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It looks like you have some chromatic aberration that becomes more pronounced after your post processing. Boosting contrast or sharpness can make it more pronounced. In the first picture, I don't see it being a problem until you converted the portrait to b&w. In the other pictures, it looks like you're dealing with high contrast scenery which can often bring out the aberration.

In photoshop, go to Filters, then Distort, then Lens Correction. Go to the chromatic aberration sliders and experiment with the values there to try and correct it. In lightroom it is under the Lens Correction section. There may not be a profile for the lens if it's an old one, so you may have to use the manual adjustments instead.
08-19-2011, 04:54 AM   #3
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Hi

Was the original image taken as JPG or RAW ?

What I see here looks like the classic JPG artifects, that is, when you do PP on 8 bit JPGs that have been heavily compressed at low quality levels. (8 bit JPGs are no good for post processing because the compression algorithm has stripped out a lot of data in order to reduce the file size)

If you want to do the type of PP (by the way PP stands for post processing) you display here you ought to shoot in RAW. The RAW file will have 16 bit which means it will give you 65,536 shades of each red, green and blue colour while JPG will only allow you to work with 256 shades per colour. 16 bit files will allow you to do much more precise colour manipulation.

You should do all your PP in Raw (as much as you can) and than save the file in TIF format which is a lossless format which in turn will allow you to do further meaningful corrections if required. Only the final image should be saved in JPG if you require this. (Preferable only once). JPG is a lossy format meaning every time you save an image in this format you loose data information, the more often you save the more you loose.

What I see in your pictures, to me, does not look like it has anything to do with the lens.

Greetings
08-19-2011, 05:28 AM   #4
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I woulf have to agree with Schraubstock/

Although I am a regular JPEG shooter, and avid supporter of JPEG shooters, I also admit that if you intend to do heavy PP then you need to shoot raw.

The problem with JPEG is not so much "loss" of data, but RAW images for pentax are 12 bits of color depth, against 8 bits for JPEG as a result, in JPEG for each color you have 256 descrete levels, as opposed to 4096 for 12 bit color when you increase contrast and saturation you can generate very large areas of uniform color, and things become patchy. I have seen this in large areas of blue sky for example.

Also as mentioned, there is some CA present, although I am not sure how much is removable in the lens profiles.

Typically there are 3 specific aspects to CA.

- there is lateral CA in the In Focus plane, where as you move out from the center of the lens, you get a separation of the colors, because the magnification of the lens is not the same for all colors. lens corrections can fix this, and if you go into the processing forum, you will see an example of a sigma lens I own, where much of the lateral CA is corrected. The Pentax Photo lab is a good tool to remove this, if you dont have photoshop.


-there is lateral CA in the out of focus detail, with similar to above, but much more pronounced separation of the colors in the out of focus region. Typically purple on one side and green on the other. The normal CA correction in the lens profiles can't do anything about this and you need to use a fringing removal tool.

- there is longitudinal ca, where out of focus in front of the plane of focus has a purple halo and behind the plane of focus there is a green halo, again this cannot be corrected in the lens correction tools in the lens profiles, and needs to be removed by fringing tools.

For the out of focus regions the best fringing tools have the ability to select the colors of fringing you want to remove, and the radius in pixles, you want to correct over. I use the pone in corel's PSP X3 for this

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