A new FZ20 user, and a cameratard needs some help.

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mbaro
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A new FZ20 user, and a cameratard needs some help.

Post by mbaro »

Well, lot's of help, actually. But one thing at a time.

Being used to point and shoots, I really have no clue about things like aperature and shutter prioty and other techy things like that, so please bear with my ignorance for a bit.

My question is, how do I get rid of the red line between the beetle and the marigold?

Image

full picture (bandwith killer) is at http://treedweller.net/journal/insectpi ... leback.jpg

The picture was taken outside, sunny day. I'm still experimenting with hobo-rigging techniques until I get a close-up lens and some filters. In this case the macro at maybe 6Xzoom, with a magnifying glass.

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twebster
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Post by twebster »

Hi ya' mbaro :D

If I understand your post correctly, this image was made with a simple magnifying lens placed over the camera lens. The red line is caused by uncorrected chromatic aberrations introduced by the magnifying lens. Simple magnifying lenses are not corrected to focus all colors on the same plane. The red line is caused by red light not being focused on the same plane as the other colors. It shows up the worst at edges that have high contrast between light areas and dark areas. If you look at your image closely you can see where the red shows up a bit in other areas, too.

The way to reduce and/or eliminate this problem is to replace the magnifying lens with a quality 2-element supplementary diopter lens ("close-up filter") such as are made by Nikon and Canon. These supplementary lenses are much, much better corrected for chromatic aberrations than magnifying glasses and simple, 1-element supplementary lenses. I hope this helps you out. :D

Best regards, :D
Tom Webster
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mbaro
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Post by mbaro »

Ah... thanks! That makes sense. I'll have to wait until christmas for someone to send me the close-up lens all the way to Maputo, but until then, oh well.

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nzmacro
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Post by nzmacro »

I used a magnifying glass for a lone time with my Sony CD-1000 and it worked well, better than it does on my Panasonic FZ10. So this may well be a difference in the camera lens as well. Some the magnifying glass works on better than others.

You certainly will get better results with a Nikon 6T for example. They are corrected to a certain degree more than single element designs.

All the best and I don't use mag glasses at all now. Still would on the Sony though if needed.

Danny.

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mbaro
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Post by mbaro »

The magnifying glass works fine on my Olympus d-510- no colour shadows or anything. Maybe it has something to do with the amount of zoom you can do?

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Post by nzmacro »

Interesting for sure :D . The Sony CD-1000 had a 12x optical zoom so that was getting up there and it worked quite well with the maggy. Mike Ash used stacked and single magnifying glasses for his macro work on a small Oly with superb results. Never noticed any colour shifts in his shots, so yep, it might well come down to the camera and the optics it uses.

I know the FZ10 doesn't like it at all :D :wink: . Its probably just an optical imbalance that it causes with certain lenses. Also different magnifying glasses work better than others. I prefer large diameter ones so we are not shooting at the sides of the magnifying glass and more toward the centre of it. Plastic or acrylic versions I wouldn't go near to be honest. They really do need to be glass.

Anyway, interesting for sure :D

Danny.

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Post by rjlittlefield »

Hi all,

I downloaded the full image. (Bit of difficulty with that -- what came down had some peculiarity such that neither Internet Explorer nor Photoshop could handle it. But IrfanView was OK with it, and after resaving I could pull it into Photoshop. Anyway...)

It's clear from the full image that Tom and Danny are spot on about this being chromatic aberration (CA). In fact this is the most extreme case of CA that I have ever seen. At the end of the beetle's abdomen, there is a whole rainbow -- the full spectrum from red to blue!

I tested some of the new software tools for digitally removing CA. I found that this image severely stresses their capabilities, although I was eventually able to get quite a bit of improvement. The shift is too much to even specify in PTLens. I can get enough shift using the Panorama Tools "Correct" filter (it's a Photoshop plugin too), but then I discovered that the RGB channels have apparently been smushed together so much in the jpeg compression that correcting the CA makes the image a bit fuzzy. This is an interesting result that I will look into for other reasons -- digital CA correction is still new enough that the limits are not fully understood.

In case you are curious, here are the results of digitally removing CA. This is a crop of the whole beetle, reduced here to about 48% of the original pixel size. As you can see, the rainbow is gone from the end of the abdomen and the red line is gone from the edge of the petal. These images have not been manually retouched, but there was quite a bit of tweak-and-test to determine proper parameters for the CA removal algorithms. In my opinion these tools are far from ready to deal with this much CA on a routine basis. However, I find it encouraging that they could do even this well.

Image

For advice, I don't have much to offer that Tom and Danny have not already covered -- try every magnifying lens that you can get your hands on, and go with whatever works best.

Be sure to keep the lens centered. While figuring out to remove your CA, I discovered that the center of the CA is not the center of the image. This probably means that your camera was looking off-center through the magnifier, which is practically guaranteed to make all aberrations worse. (It also wreaks havoc with the tools -- I had to manually recenter to get the algorithms to work right.)

Since you're new to macro work, it's worth mentioning that the normal lens from a 35mm SLR, reversed, often makes a great macro lens. Poke through the photomacrography.net articles for guidance about how this works.

Best of luck, and we look forward to seeing more images in the future. This one shows a lot of promise :) .

--Rik

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Post by nzmacro »

Much better. Well done Rik. I'm having trouble downloading that shot as well. With Photoimpact when I use the noise removal feature, it often sees CA as noise. Now I have no idea why, but it seems to shift quite a few colours to line up. Yep, I know that sounds crazy but it seems to work. I'll see if I can get a screen shot of it next time. Always fascinated me why with Photoimpact.

Anyway, nice work Rik. :D :wink:

Danny.

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mbaro
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Post by mbaro »

Thanks for your help and suggestions!

What mainstream (PC-based) programs can I use to get rid or at least minimise the CA? I have Photoshop 7 and Paintshop Pro 7/9/Studio (I think Studio might be able to do the job, but I need to install it first)?

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Post by rjlittlefield »

mbaro,

These are the ones that I know about.

Step 0 is always to reduce the CA as much as possible by optical adjustments. You will get better results with less work.

Step 1, download PTLens from http://epaperpress.com/ptlens/. PTLens is a Photoshop plugin (for Windows only) with excellent capabilities to remove several kinds of lens defects including chromatic aberration, barrel/pincushion distortion, and corner falloff (vignetting). It has an easy to use graphical interface with a good preview window and sliders to control the CA correction.

Step 3 -- only if necessary -- is to download the Panorama Tools plugins from http://epaperpress.com/ptplugins/index.html. (Yes, it's the same developer -- a very nice man by the name of Thomas Niemann.) These are Photoshop plugins also. They have a clunky user interface but are more powerful than PTLens in some situations. In particular, you can correct huge amounts of CA with the PTCorrect plugin. Use Filter | ePaperPress | PTCorrect, checkmark Radial Shift, click the Options button next to it, set the "d" values (last column) for red and/or blue slightly different from 1 (like 0.99 or 1.01), and click OK | OK to see the effect. (Sorry, no real-time preview.) Do not mess with the other parameters -- they are for dealing with more complicated forms of CA and are notoriously difficult to control.

Note that both of these tools assume that your CA is centered. If it isn't, you'll need to increase your canvas size and move the image around until the CA is centered, then apply the tool.

For the work posted earlier in this thread, I ended up having to use PTCorrect because PTLens wouldn't give me quite enough correction. For PTCorrect, I believe that I used red d=0.99 and blue d=1.015. I also had to enlarge the canvas by several hundred pixels and shift the image down and to the right to center the CA. (Sorry, I don't remember exactly how much.)

I'll be interested to hear what tools/techniques other people know of. There is another thread on CA right now in the techniques forum, (http://www.photomacrography1.net/forum/ ... php?t=3147), but it seems to be very quiet.

--Rik

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mbaro
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Post by mbaro »

Thanks! I'll definitely play around with these soon!

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