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Author Topic: Helicon Focus: Optimum number of slices?  (Read 1445 times)

Hening Bettermann

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Helicon Focus: Optimum number of slices?
« on: July 03, 2010, 04:36:39 pm »

Hi!

So far, I have followed Bernard Languilller's advice to take twice as many shots as one thinks would be necessary, and without having done any comparison, I feel I have fared well.

Now, I am confused  to read that perfectionistic Joseph Holmes favores just 2 or 3  shots per frame.

"It is much easier to blend a series of images of a flat surface together than a set of images which contains something very close in front of something very far. In the latter case, the best results are likely to obtain from stopping down relatively far and using correspondingly fewer exposures to make the set. "
 http://www.josephholmes.com/news-heliconfocus.html

Spontaneously, I would have drawn the opposite conclusion.

Can somebody shed some light on this? Thank you.
« Last Edit: July 04, 2010, 08:32:13 am by Hening Bettermann »
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Michael Erlewine

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Helicon Focus: Optimum number of slices?
« Reply #1 on: July 04, 2010, 04:48:42 am »

It looks like Joseph Holmes is using medium format cameras, which I don’t have. But using a DSLR, the number of layers per stacked photo depends on a number of factors:

(1) The Type of Lens. If you are using a wider-angle lens, you need fewer layers because each layer takes in more of the subject in one shot. If you are using a macro like from 100mm-200mm you are taking in less of the subject with each photo and probably need more layers. If you are shooting landscapes and not close-ups, then a few layers will do it because you can't see any artifacts, for the most part.

(2) Front to Back. If your subject from front to back is very deep and has layers that protrude over the background (like branches of a tree) and you want the background sharp as well, then you need very short increments between photos or too many artifacts will accrue.

(3) Your Goal. If you want a micro-photography-style shot, where everything is in perfect focus, you may need a focus rail and a great many shots. If however, you are sampling the image to gain an overall impression, then you can experiment with fewer layers and make the resulting artifacts a feature rather than a liability. Focus stacking, by definition, is a sampling technique that is impressionistic, while any standard one-shot photo is a smooth linear transition from front to back, but not with everything in focus.

The bottom line is that you can answer your own questions by actually just experimenting with stacked photos to see what works best for you. If it helps, I have a free ebook on DSLR focus stacking at http:www.macrostop.com.
« Last Edit: July 04, 2010, 04:49:53 am by Michael Erlewine »
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Hening Bettermann

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Helicon Focus: Optimum number of slices?
« Reply #2 on: July 04, 2010, 08:31:38 am »

Hi Micheal,

thank you for your extensive answer and your eBook. I had earlier downloaded and studied it and had a question to which I may return. For now, your answer seems to indicate that I'm well advised  staying with my hitherto praxis, since my goal is "sharp from here to infinity" rather than an impressionistic image.

Thanks again - Hening.

Jack Flesher

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Helicon Focus: Optimum number of slices?
« Reply #3 on: July 04, 2010, 10:10:02 am »

I tend to look at the primary subject matter from each capture I want in crisp focus, then take enough frames to get all of that.  If it's everything from 3 feet to infinity with my MF back, then that usually means at least a half dozen or more captures. If it's only three subjects, a close, a mid and infinity, then 3 would do it -- I find it's easier to use the mask-blend tool with fewer images and get a result with less ghosting, possibly what Joe meant by fewer frames.  

As mentioned above, once you're in relatively close or macro ranges, then you'll need more stacks for the blend, but due to the lesser range of lens extension, ghosting is less a problem.
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Hening Bettermann

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Helicon Focus: Optimum number of slices?
« Reply #4 on: July 08, 2010, 04:42:48 pm »

Thank you Jack.
Typically I want sharpness from near to infinity, and typically, I end up with about 10 slices or so. I had planned to focus on the most important parts, and to be able to do this without having to re-focus between shots, I have equipped (so far one of) my lenses with a mm scale glued over the existing m/feet scale, and had thought to jot down values for the most important image details and shoot at these positions. However, it turns out that 1- this still takes too long time 2- I find everything equally important, so I end up using the scale only to shoot at about evenly spaced distances.
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