Focus Bracketing R6

Started 2 months ago | Questions thread
Karl_Guttag Senior Member • Posts: 1,138
Re: Focus Bracketing R6

Phylloxera wrote:

Simplifying macro stacking by focus bracketing was one of my reasons to buy an R6.

First problem: setting the focus increment FI). The distance of the steps are arbitrary units on a scale 1-10 and the value has to be guessed more or less because it is depending heavily on the focus distance and the focal length of the lens.

Here some crude values obtained with the EF 100 2.8 Macro. CR3 files were developed and stacked with Helicon focus 7 without any problem.

Focus distance FI setting Actual increment per step

0.3 m (1:1) 10 0.6 mm

0.5 m (1:4) 10 3.5 mm

1.5 m (1:10) 4 15 mm

If someone has experiences with this lens or other ones I would be grateful to get more values and comments This might save a lot of testing time for all beginners in this technique ...

I ran a few experiments to "decode" the algorithm using the RF100f2.8 Macro. In this experiment, I shot a ruler and then went through the photos to see how the focus moved (how many shots per 10mm increment in focus).

It seems the camera is computing a formula based on the lens, f-number, and focus distance. I have verified a few times that the focus stepping is inversely proportional to the f-number. So if you say double the f-number, the number of focus steps is half for the same range.

One other thing I noted with the RF100 Macro is that there is considerable "breathing" when shooting a focus stack starting from minimum focus distance. See my 3rd post on that topic:

From some of my earlier experiments, the default F.I. of 4 seems to be about right. Going with an index of much more than 4 will cause some visible focus "wobbling" (blurring) between images. Smaller indexes will probably be better, but you have many more images to combine, and it takes longer to shoot (more time for something to move).

I expect there will be some similar issues concerning f-number if the lighting is not an issue. At higher f-numbers, there are fewer images to blend, but there is more of a focus difference between shots at the same F.I. number.

 Karl_Guttag's gear list:Karl_Guttag's gear list
Canon EOS R5 Canon RF 15-35mm F2.8L IS USM Canon RF 24-70mm F2.8L IS USM Canon RF 70-200mm F2.8L IS USM Canon RF 24-240mm F4-6.3 +13 more
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