View Full Version : Iris

Ron Conlon
05-09-2015, 07:31 AM
A composiite (focus stack) of about 30 images. Flash from the side, the background is a day lily, an iris blossom stuck in the day lily, and a printed background behind that.
D800E 200mm f6.3 1/200 ISO100

John Robinson
05-09-2015, 08:48 AM
Hi Ron
Good subject and I like the BG. The back petal ofthe iris does look a little soft in the yellowish area. Could be my old eyes !I would have thought 60 pics would cover it. Doesn't taking so many shots duplicate a lot of frames ?/
What is the DOF with that set up at 6.3?( I don,t know what distance tou are at)
PS Just done a rough calculation, and if you were at about 6 feet from the flower you should have 2 centimeters DOF. Wouldn,t 6 or 7 shots cover it ?

Ron Conlon
05-09-2015, 12:27 PM
I will do the calculations for my set up, I haven't done them out of laziness--easier to let the mac do the work. But I should do the basic calculations out of curiosity, and also for the future to resolve this matter and so that my mac doesn't overheat.
For the Zerene software I use they recommend a certain amount of overlap (I forget how much, will look it up). Also I am a good deal closer than 6 feet. Those combined should require more frames, but I may still be over-shooting.
I had assumed that the tethering software would do the calculations--it should have all the information it needs, and algorithms like that are what software is for--but it just notes the start and end points and then proposes to shoot every shot at the minimum step of the focus set in software.
I think the softness you refer to may be due to overlap/crossing rather than a missing shot--when two objects are front-to-back separated by a longer distance, the out-of-focus near object (larger and fuzzier when out of focus) obscures the back object when the lens is focussed on the back object. Other than cloning in bits from elsewhere I know of no other way to correct it, because it was never there in the original stack and you couldn't get it sharp anyway because of the problem I described of the near object fuzzing out larger...

John Robinson
05-09-2015, 01:56 PM
Certainly interesting. I was only guessing at the distance . I went out and tried a 200 lens on an Iris, Maybe mine was a big one !!

Jerry van Dijk
05-09-2015, 04:39 PM
What a lovely image. The exposure is spot on, emphasizing the soft colors and details on the petals. I like how the flower is "echoed" in the BG. I think I would have preferred a little more room on the right, putting the top petal around the ROT line on the right hand side.

Ron Conlon
05-09-2015, 07:07 PM
Thanks, Jerry.
John, it is a small iris, though not the smallest. And my camera is full frame (putting me closer) to your usual Dx.
For 2ft distance 200mm f6ish, full frame various online calculators give me a good deal less than a cm, and a surprisingly broad range of results.

Diane Miller
05-10-2015, 06:34 PM
Lovely rendering of a lovely flower -- I can smell it!!

All the DOF calc's I ever find give me a lot more DOF than I'm happy with. They apparently assume an acceptable circle of confusion more appropriate to 35mm film and old lenses, and not adequate for the resolution we have these days.

Here's a thought for the overlaps. What if you shoot a sequence, then manage to cut off the offending front petal and shoot the back one with nothing in the way. Would at least give you clean cloning material, if you could keep the flower in close enough to the same position.

Ron Conlon
05-11-2015, 06:06 AM
Perhaps I just need to determine the number of frames empirically. I had done that once, stacking every second, third and fourth frame. My distance and aperture doesn't change much, so of I do a few more I can say with confidence how many frames I need (or which multiple of the minimum focus steps that the tethering software uses I need to follow).

Cutting the petal is a solution, but there is no going back from it. I would need to carefully check the series to make sure I am happy (except for the overlap).

Thanks, Diane, always insightful.