Friday, 23 May 2014

DOF and diffraction part 2 - the software: hugin, photoshop and helicon focus

As soon as I looked a little harder at the output from enfuse, I realised that there were some strange things going on....

This first crop is the output file which at first glance looks promising - the card and the distant hedge are both looking reasonable,but there is a bit of a dark halo around the black lines as well as a thin line in the centre of the black line which is darker than the rest.
Here is the image from the stack where this card is in focus. not only is the strange halo absent, but there is a lot more texture detail showing up in the card surface.

Clearly there is detail in the stack that does not make it through the process... 
Here is a quick go with two other obvious contenders for focus stacking:

photoshop CC

Helicon Focus

The output from Photoshop CC, which claims to be able to focus stack, but in reality make a complete mess of it. This crop shows that it has failed on the distant hedge immediately above the card and also there are some wierd things going on with the railings. the output from Helicon focus using all default settings. This looks much more promising - there is a small area of softness immediately around the card, but this is where the distant focus image has blurred white from the card into the foliage, so this is actually a sensible default.
I gave CombineZP a quick go as well, but it crashed most reliably on all but the simplest mode, and in that mode it's output was nowhere near as good as Helicon.

Read on for info on how enfuse and photoshop get it so wrong, and why Helicon focus looks to be the best option.

Tuesday, 20 May 2014

the dof and diffraction trade-off

Sometimes physics is a real bummer, and trying to win depth of field to maintain crisp images for things near and far (especially with longer focal lengths) quickly falls into the pit of diffraction, which just makes everything go soft.

So how bad is it really and what can help? I'm exploring some of the options with my 70-200mm zoom. I set up a simple test scene along the side of the house (facing north so no direct sun, although mostly cloudy anyway..). Hopefully this will develop into a method for using DSLR-controller to take the pictures, and then hugin tools to automate the blending process.

Here are the limits of what happens, these are crops from a MUCH larger photo basically out-of-camera, and F32 is really loosing a lot. These crops are from the little square towards the bottom left of the picture.

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F2.8. .F32