Photo stacking

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

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Tonyphotoplus
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Joined: Sun Apr 11, 2010 4:20 am
Location: West Wales

Photo stacking

Post by Tonyphotoplus »

I am hoping I will be able to get some help here as I am having problems getting the stacking correct. I have a Nikon D5000 witha Tamron 90mm macro lens. I use CS4 for stacking.
I took 16 images of a lesser celandine with a tripod. The proble is that the variations in focus makes the image smaller as I started at the front of the flower.
This is the first image
Image
This is the last
Image
And this is the layers in PS
Image
Photoshop made a poor rendition of teh subject and so did CombineZM. I have asked others and they keep telling me I moved the camera and all the things I have not done. It was stable and on a tridop and the setting remained the same through out. The only thing I moved was the focal point at various stages as you should. Is there anything I should be doing or missing here. I did tell PS to auto align as well to try all sorts of methods to resolve teh problem. This is my first entry into stacking. Looking forward to seeing your replies

Thank you

lauriek
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Post by lauriek »

The best thing to do if you suffer from the rear-most picture being too small is to start at that end of the stack and set the magnification to the correct amount for that image, then work forwards..

Do you have an example of the output, no matter how bad it looks. It's hard to say what's going wrong without seeing that!

ETA Welcome! :) (I just noticed this is your first post!)

ChrisR
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Post by ChrisR »

Welcome Tony.
Don't worry, it's all normal!

While you don't think you're changing anything, you are really. You have to move something to get the right part in focus. When you do that, lots of things change.

I imagine you're just turning the focus ring on the lens, which is fine, but that changes both the distances between the sensor and the lens, and the lens and the subject.

Two key things result. One is that your angle of view has changed. That means that the flower gets bigger in the frame, and you lose the tips of the petals. The ONLY part you can have in your final picture is what's covered by the narrowest angle. It's what's between the dotted green lines, below.
The second thing that changers is the perspective. The picture you get from each exposure is the lens's view of the subject. You're moving the lens. It's pretty near the subject, more so with shorter focal length lenses. That means that the perspective changes considerably on every shot.

Those two things give the aligning part of the stacking process a hard time. They're all designed to cope, but their abilities vary, and some have to be controlled. You can get strange effects, like curves in the output which weren't there in the subject.

This takes a little while to grasp, and there's a lot more to go into. Read around the site and you'll find the same subject being grappled with several times. It sinks in better when you've read more than one different explanation
In the meantime though, move back a bit; you'll get it all in, and the angles won't change so much when you focus.

This might help.
As you focus, you move the lens from red to blue. You can see how the fov changes.


Image
Does that help?!?

I'm trying to avoid complication but have to add one unknown. Many macro lenses actually change their focal length when you focus them close. I don't know about your lens. It doesn't make a showstopping difference, but can lead to more confusion. There are always complications, and as always, they conspire against you!

rjlittlefield
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Post by rjlittlefield »

Tony, welcome aboard! :D

There is some discussion of focusing and framing in the stacking tutorial HERE. Notice that either front or back can be the narrowest frame, depending on how you adjust focus. It looks like you're turning the focus ring, which is typically the better thing to do at lower magnifications.

I agree with ChrisR's advice and reasons: move back, so you get everything you care about in the narrowest frame and reduce the changes in perspective as you shift focus.

As lauriek says, we need to see your output to tell what is going wrong. There are lots of ways for stacking to go bad, all of which can be described as "poor rendition".

--Rik

elf
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Post by elf »

Step 1. Throw away CS4
Step 2. Get Zerene Stacker
Step 3. Do a focus stack in Zerene Stacker

Focus stacking programs can handle the changes in magnification (CS4, however, is not very good at it)

Tonyphotoplus
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Joined: Sun Apr 11, 2010 4:20 am
Location: West Wales

Post by Tonyphotoplus »

Thank yo so much. I tried to ask on other forums and they had no idea of stacking. You have been very helpfull and I will go through your links and soak it all in. Its all very interesting thank you. And I will keep experimenting and see about that software

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