Tiny flower focus stack. Successes and failures.

[407370]

Hi all,

To set the scale I am working at, here is a pic of the flower next to my finger print:

I setup in my studio (garden shed) with a GODOX V1 as an off camera flash. I decided on this setup after much testing of various diffusors:

The subject flower is so small I thought I could get a sharp pic of the whole flower with a higher aperture (f40):

As you can see that did not work. I did try at f16 but it was not much better.

I started Focus stacking at f5.1 and 20 images:

Dont you love a good halo . I applied a 1 stop exposure compensation and tried again:

Halo not as obvious but still a bit unsharp.

So tried again with the following settings:
Aperture - F5
40 Image stack
Focus step - 1
Delay - 3 seconds
Exposure Compensation minus 1.7

Helicon Focus render settings:

Final result:

All in all a very informative little session.

Any and all comments welcome.

CHEERS
JBO

 

[smoke665]

Even with a 40 stack image, there appears to be an area of OOF right in the center. I suspect what your missing here is that DOF is a function of aperture, distance to subject AND focal length. For example, comparing a popular brand combination at a minimum focus distance of 12" at f/5 a 35mm lens has a DOF of .51 inch, while a 100mm lens at the same settings only has .05 inch. moving to a distance of 36" with same settings, the 35mm has a DOF of 4.97 inches while the 100mm is only .56 inch. Shifting to a 200 mm which I've done at times you'd need to be at 69" from the subject to equal the same DOF as the 35mm at 12".

I don't remember the exact distance from the subject on this one but it was probably in the neighborhood of 36". The flower is comparable in size to yours, no focus stack, 100mm, f/25, 1/125, ISO 800. Ambient light and reflector. Whether it's one shot or a focus stack, you still need to consider your DOF when choosing focal length/distance/aperture and if doing a focal stack, adjust your image stack number to cover the desired total DOF.
Pretty In Pink by William Raber, on Flickr

Here's an interesting link on calculating step size in a focus stack. stacker:docs:tables:macromicrodof [Zerene Stacker]

 

[407370]

Even with a 40 stack image, there appears to be an area of OOF right in the center. I suspect what your missing here is that DOF is a function of aperture, distance to subject AND focal length. For example, comparing a popular brand combination at a minimum focus distance of 12" at f/5 a 35mm lens has a DOF of .51 inch, while a 100mm lens at the same settings only has .05 inch. moving to a distance of 36" with same settings, the 35mm has a DOF of 4.97 inches while the 100mm is only .56 inch. Shifting to a 200 mm which I've done at times you'd need to be at 69" from the subject to equal the same DOF as the 35mm at 12".

I don't remember the exact distance from the subject on this one but it was probably in the neighborhood of 36". The flower is comparable in size to yours, no focus stack, 100mm, f/25, 1/125, ISO 800. Ambient light and reflector. Whether it's one shot or a focus stack, you still need to consider your DOF when choosing focal length/distance/aperture and if doing a focal stack, adjust your image stack number to cover the desired total DOF.
Pretty In Pink by William Raber, on Flickr

Here's an interesting link on calculating step size in a focus stack. stacker:docs:tables:macromicrodof [Zerene Stacker]

Fascinating as all those facts and figures are......... there is no way of using the resulting number.

I dont measure the flower and then measure the distance to the flower and calculate the DOF (considering the focal length of the lens) as there is no way of inputting that figure into the camera or there is no way of accurately calculating how many shots at a given DOF is required to encapsulate an entire object.

If I set focus step width at "5" then move the camera and object closer together or further apart the same setting will result in bigger or smaller steps between shots. There is no practical method of predicting how big that step will be. Through experience I know at minimum focus distance using MC105MM at F5 / Focus Step 1, I will get the sharpest / best output from focus stacking tiny objects. Bear in mind that DOF used in my example is less than 1mm (0.0393701 Inch)

The flower you used as an example is inappropriate for the post I made as it is 100 times bigger than the flower I was photographing. This example you posted also has a background thats in focus. That is a result I am not looking for. Even if you moved the lighting closer to the subject it would be difficult to invoke "Inverse Square Law" because of the huge DOF

The OOF area you are referring to is a shadow from the side lighting.

Thanks for the input.

CHEERS
JBO

 

[smoke665]

I dont measure the flower and then measure the distance to the flower and calculate the DOF (considering the focal length of the lens) as there is no way of inputting that figure into the camera

Ahh, I should have looked closer at your setup. In camera focus stack is handy but lacks the precision of a focus rail. There are numerous price points on Focus Rails depending on the accuracy you want to achieve.

no way of accurately calculating how many shots at a given DOF is required to encapsulate an entire object.

Using your method there isn't, but using an accurate focus rail and the link I posted, it's quick and easy, with no guessing-

1. Use Table 1 to determine magnification, by framing your subject and measuring the frame width.
2. Use the second table to choose an aperture setting and determine the associated DOF and maximum step size. Use the bold settings
3. Test and adjust if necessary.
4. Once you have the step size, divide the total DOF required by the step size to get your toal steps. For example if your measured frame width is 35mm on a full frame camera, your magnification equal 1. Using the 2nd table you read on the magnification line of 1 and an aperture setting of f/5.6 the middle step size setting is .28mm. If your total DOF equal 20mm, then 20/.28=72 steps (rounded up)

The flower you used as an example is inappropriate for the post I made as it is 100 times bigger than the flower I was photographing. This example you posted also has a background thats in focus. T

You are incorrect, the flower in my shot was fingertip size same as yours, the insect at the top was tiny, didn't even notice till I stared working on the image post. This was shot in the woods, lots of unattractive stuff around/behind the flower, it was cropped, selected, enlarged, and a complimentary color canvas texture, background added post. Nothing there to be in or OOF, no different than the black poster board you used.

The OOF area you are referring to is a shadow from the side lighting

Not referring to shadow, but the small OOF area in the center of the flower toward bottom left. Not overly visible till you blow it up, but it's there.