My quest to "fine tune" and understand my setup.

Just bought that first macro lens? Post here to get helpful feedback and answers to any questions you might have.

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skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

5. Use an extra aperture in the back of the Raynox.

In this test I use an extra aperture in the back of the Raynox lens. One with 18 mm aperture and the other with 10 mm aperture.
Image

One problem with the extra aperture is quit a lot of vignetting.
Examples with zoom=24 mm, 50 mm, 107 mm and 215 mm

First without extra aperture:
ImageImageImageImage

With 18 mm extra aperture:
ImageImageImageImage

And finally 10 mm aperture:
ImageImageImageImage

And a comparison of 100% crops. All images are stacked.
From left to right: No aperture, 18 mm aperture, 10 mm aperture.

Zoom 24 mm

ImageImageImage

Zoom 50 mm

ImageImageImage

Zoom 107 mm

ImageImageImage

Zoom 215 mm

ImageImageImage


No imrovement with shorter zoom settings but a significant improvement at full zoom where the normal result is really bad.

Next step will be to check at what zoom settings it starts to improve the result and then it will be on to teleconverter 2x :)

/Leif K

Lou Jost
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Post by Lou Jost »

Very interesting, thanks for posting these for all of us who use Raynox.

skrylten
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Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

Here is one extra test with the 10 mm aperture at zoom = 118 mm and 141 mm.

Crops at 100%, left without aperture, right 10 mm aperture.

Zoom 118 mm
ImageImage

Zoom 141 mm
ImageImage

It looks like its only at the longest zoom settings the extra aperture will improve the image.

skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

6. Use cameras built-in teleconverter

The camera has a built-in digital Teleconverter (1,5x or 2x).
This test is to compare the best images from "test 5", with images of the same field of view but "zoomed out" combined with the 2x Teleconverter.

From left to right: Best image test 5, 2x TC, 2x TC + 10 mm extra aperture.

Zoom 24 mm without TC and 11 mm with TC
ImageImageImage

Zoom 50 mm without TC and 29 mm with TC
ImageImageImage

Zoom 107 mm without TC and 50 mm with TC
ImageImageImage

Zoom 215 mm without TC and 80 mm with TC
ImageImageImage

And finally at max zoom (215 mm) + 2x TC.
Right one with 10 mm extra aperture.
ImageImage

I set the zoom "by hand" and didnt hit the exakt setting to match 2x but my conclusion is to avoid the built-in Teleconverter unless I need a higher magnification than full zoom or if I want to do a quicker stack with less focus steps.
Last edited by skrylten on Sat Sep 03, 2016 3:45 am, edited 1 time in total.

Grahame
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Joined: Tue Sep 30, 2014 11:36 pm
Location: New Zealand

Post by Grahame »

Hi Leif
No zoom data showing on the set of images.
I can guess.
Interesting :)

skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

I missed that Grahame, will edit the post :wink:

Grahame
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Location: New Zealand

Post by Grahame »

Interesting what a difference the 10 mm aperture makes.
Guess I better find a way of making one :)

skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

7. Flash setting and shutterspeed

The camera has 3 different flash powers, low, medium and full.
Its possible to use first or second curtain sync. Its an electronic shutter and I think the curtains specify how to read the pixels from the sensor.
I´m using second curtain but I dont think it makes any difference in my set up.

With my milk-bottle diffuser the low flash power doesnt give enough light so I have to stick with medium and full power.

Slower shutter speeds ( longer than ~ 1/1000 s) doesnt have any impact on the image (its all about the flash) but I can use CHDK to override the shutterspeed when I need faster shutter speeds.

Here are some examples of single images with correpsonding histograms.
F 7,1, ISO 80, Zoom 129 mm

From left to right:
- Medium flash 1/1000 s
- Medium flash 1/40000 s
- Full flash 1/6400 s
- Full flash 1/10000 s
- Full flash 1/40000 s

ImageImageImageImageImage

ImageImageImageImageImage

Which one to choose and why ? Maybe it doesnt matter ?

This is 100 % crops with adjusted brightness and contrast and with corresponding histograms.


ImageImageImageImageImage

ImageImageImageImageImage

Looking forward to input on how to choose :wink:

rjlittlefield
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Post by rjlittlefield »

skrylten wrote:Its possible to use first or second curtain sync. Its an electronic shutter and I think the curtains specify how to read the pixels from the sensor.
I´m using second curtain but I dont think it makes any difference in my set up.
Right. The main difference would be if you had a moving subject plus enough ambient light to register during the exposure. In that case second-curtain sync will flash the subject at the end of the exposure, so any streak from the ambient illumination will appear "behind" the main exposure in terms of movement. This is the effect that we normally want to see. In contrast, first-curtain sync will flash the subject at the start of the exposure, so any streak from the ambient exposure will be captured later and will appear "in front of" the main exposure in terms of movement. This looks odd. See the illustrations at http://neilvn.com/tangents/first-curtai ... tain-sync/ .

--Rik

skrylten
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Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

8. How to align images for noise reduction and superresolution

This post should be about aligning images but I will start by having a look at a single image and try to get rid om some abberations (if possible).

The test images are of som printed dots on white paper.
Zoom 164 mm, F 6.3 and 1/8000 s

First the whole image followed by 100% crops of a dot in the center and a dot in the corner.

ImageImageImage

A lot of transverse chromatic abberation in the corners ...

Another intresting comparison is to split the image into the different color channels.
From left to right the: red, green and blue channel of 4 consecutive focus steps.

ImageImageImage
ImageImageImage
ImageImageImage
ImageImageImage

To me it looks like there is a full focus step of distance between the different color channels in axial chromatic aberration.

My first thought was to combine color channels from different focus steps to combine a new improved image but I think it should be even better to stack each channel separately and then combine them to a new image.

Here are 100% crops of a single image followed by a "normal" stack and finally a stack with color channels stacked separately.

ImageImageImage

And here is the difference of a dot in the corner. The red "top" is from aligning the color channels.

ImageImage

It seems like its possible to improve on both axial and transverse chromatic abberation with this aproach and get a stacked image that "looks better" than what can be seen in the focused part of a single image. That was interesting for me ...

skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

8. How to align images for noise reduction and superresolution, part 2

The small sensor in the SX50 is quite noisy but I can reduce the noise by taking several images at each focus step and use the median value of them to create a noise reduced image.

This test is to see if the images need to be aligned and if a "simple" alignment is enough.

The test image is the green colorchannel of a butterfly wing.
Zoom 107 mm, F 6,3, 1/8000 s, 100 % crops

First a single image.
Image

And next noise reduced images with different alignment of 9 separate images.
From left to right:
1. No alignment.
2. Standard alignment with align_image_stack ( downscaled by factor 2, 5x5 grid with 8 control points per grid.
3. align_image_stack with no downscaling, 10x10 grid with 16 control points per grid.

ImageImageImage

I think there is need for alignment but the standard alignment will be enough.

I need to type a lot of commands and parameters with these tests and to make my life easier I have made an "embryo" of a "Stacking GUI" based on a hta file and VBscripts. I will try to update this GUI along with the tests .

Image

skrylten
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Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

9. How to handle "inversed perspective", part 1

This is the post that so far has given me most headache to wrap my head around. Part 1 will be to describe the problem and have a first shot to handle the strange perspective.

First some images to describe the problem. 3 images at each zoom setting:

Left: focused at closest possible focus point.
Middle: Focused "midway to infinity".
Right: Focused at infinity.

Zoom 52 mm
ImageImageImage
Zoom 103 mm
ImageImageImage
Zoom 193 mm
ImageImageImage

At full zoom the subject is 50% bigger at infinity focus than at closest focus point.

To se the effect on a stacked image I did a stack with 103 images at full zoom (215 mm) of an Iphone 4 screen.
ImageImage

In the stack it seems like the screen is curved and closest to the camera at the right side :D

My idea to improve the result is to scale the individual images based on zoom setting and focus.
In this first attempt I used a third order equation to scale the images and got this result (crop to the right)
ImageImage

Better but very flat compared to the angle of the Iphone4 screen.

Next test was to add more scaling in an attempt to get some perspective in the image.
ImageImage

Now it looks better but its obvious the third order equation isn´t correct.
In part 2 I will try to improve the scaling of the images to get a more linear result in the stack.

/Leif K

rjlittlefield
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Post by rjlittlefield »

Not sure if this will help solve your problem, but see http://www.photomacrography.net/forum/v ... 0750#50750 for an explanation of why your perspective is inverted.

--Rik

skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

9. How to handle "inversed perspective", part 2

Thanks for the link to that post, Rik. It really gives me a better perspective on my issue :D

By scaling the images I am now able to get a flat view of the stack or some perspective that maybe makes it easier to understand the geometry of the subject.

Left: Stack without scaling of images.
Middle: Scaled to get a flat view
Right: Scaled to get a perspective.

ImageImageImage

skrylten
Posts: 60
Joined: Fri Jan 03, 2014 1:41 pm

Post by skrylten »

10. Noise reduction with several images/step

There is quite a lot of noise in a single image but by taking several images at each step and combine them into one image I can reduce the noise.

Here is a comparison of a single image and the median value of 3, 5, 9, 15 and 27 images. They are close to 6x their actual size.
Images taken at zoom 83 mm.

Image
Image

Its possible to see an improvement at least up to 27 images per step.

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