I was asked this question recently, started to respond, then realised I didn't understand well enough to construct a good answer.
The focus on a macro lens can be controlled by software, so that it takes a series of shots at different focal distances. These can then be stacked.
Stacking can also be done with focus rails, bellows, precise mechanical movement of the subject or the camera in small steps.
Q: That sounds like an awful lot of extra equipment and bother, when you can just control the lens with free/cheap software. What is the advantage of the mechanical movement method?
My initial thoughts on an answer included
- more repeatable and finer steps (but how much, and is that really true)
- less change in magnification across the stack (but software seems to cope)
- can use non-autofocus lenses (my main reason, personally)
- um
Stacking by autofocus vs. stacking by movement
Moderators: rjlittlefield, ChrisR, Chris S., Pau
-
ChrisLilley
- Posts: 674
- Joined: Sat May 01, 2010 6:12 am
- Location: Nice, France (I'm British)
AFAIC the biggest problem with software controlling is lenses. How often do you use a mechanical setup with an out-of the-box macro lens that would also be suitable for software control? (My sigma 150 for instance was not compatible according to the EOS utility)
Admittedly I do sometimes use an out-of the-box macro lens in the field, but then again what is more cumbersome there: a rails and/or bellows or booting up a net/notebook, connecting the cables, and then fiddling with software settings on a screen that is, at best, hard to read in daylight ?
Admittedly I do sometimes use an out-of the-box macro lens in the field, but then again what is more cumbersome there: a rails and/or bellows or booting up a net/notebook, connecting the cables, and then fiddling with software settings on a screen that is, at best, hard to read in daylight ?
Jacco
Holey Moley guys. I just installed Bracketeer, took 2 seconds. I plugged in the T1i to a USB port, turned on the camera, started Bracketeer.
The live view button on the software would not turn on the camera live view, but it do show all the other settings of the camera, ie, Tv Mode, ISO, shutter speed etc. I got my manual out and read how to set the camera on it's live view. When I did that, live view came up on the screen of the software dashboard.
I use a Sigma 105, and older one, and the Dashboard buttons did control the focus motor just fine. I tried several stack shot configurations and they all worked just fine, even the tiny movement button controlled my lens perfectly.
The only thing I did not like is, it saved the RAW images to the same folder I installed Bracketeer to. Not a problem, I can just drag them to another folder. Maybe I can reset where to save in the program, didn't check yet.
So, on Windows XP Pro, this little jewel works just fine. Two thumbs up.
The live view button on the software would not turn on the camera live view, but it do show all the other settings of the camera, ie, Tv Mode, ISO, shutter speed etc. I got my manual out and read how to set the camera on it's live view. When I did that, live view came up on the screen of the software dashboard.
I use a Sigma 105, and older one, and the Dashboard buttons did control the focus motor just fine. I tried several stack shot configurations and they all worked just fine, even the tiny movement button controlled my lens perfectly.
The only thing I did not like is, it saved the RAW images to the same folder I installed Bracketeer to. Not a problem, I can just drag them to another folder. Maybe I can reset where to save in the program, didn't check yet.
So, on Windows XP Pro, this little jewel works just fine. Two thumbs up.
-
rjlittlefield
- Site Admin
- Posts: 23597
- Joined: Tue Aug 01, 2006 8:34 am
- Location: Richland, Washington State, USA
- Contact:
Re: Stacking by autofocus vs. stacking by movement
- more repeatable and finer steps (but how much, and is that really true)
It's probably true but not important. After all, the basic requirement is to get everything in focus in some frame, and autofocus systems are designed to focus adequately at any distance in their range. Sure, a screw driven rail can move by a few microns per step, but at magnifications where autofocus lenses work, there's no value added by using such fine movements.
- less change in magnification across the stack (but software seems to cope)
This varies, and as you say, software can cope with changes in magnification.
Changes in entrance pupil location are more interesting. Again there is variation. Some lenses focus by moving only elements that are behind the entrance pupil, in which case the entrance pupil does not move at all. These lenses can give some very cool effects, such as Macro landscape stack using compact digital camera. Other lenses do move the entrance pupil as they focus. For some lenses, you get very different changes in perspective depending on how you focus. See the Zerene Stacker tutorial #2 for illustration, paying particular attention to the difference between the two focusing methods.
- can use non-autofocus lenses (my main reason, personally)
Mine too.
Bottom line is that as far as I know right now, the motorized focus technique should work fine whenever it works at all.
--Rik
It's probably true but not important. After all, the basic requirement is to get everything in focus in some frame, and autofocus systems are designed to focus adequately at any distance in their range. Sure, a screw driven rail can move by a few microns per step, but at magnifications where autofocus lenses work, there's no value added by using such fine movements.
- less change in magnification across the stack (but software seems to cope)
This varies, and as you say, software can cope with changes in magnification.
Changes in entrance pupil location are more interesting. Again there is variation. Some lenses focus by moving only elements that are behind the entrance pupil, in which case the entrance pupil does not move at all. These lenses can give some very cool effects, such as Macro landscape stack using compact digital camera. Other lenses do move the entrance pupil as they focus. For some lenses, you get very different changes in perspective depending on how you focus. See the Zerene Stacker tutorial #2 for illustration, paying particular attention to the difference between the two focusing methods.
- can use non-autofocus lenses (my main reason, personally)
Mine too.
Bottom line is that as far as I know right now, the motorized focus technique should work fine whenever it works at all.
--Rik
Any of the techniques will work for single frame stacks. The first focus stacked images I did were panoramas and I used lens focusing. Usually the parallax errors could be disguised, but the failure rate was quite high. This led me to develop my current system where everything rotates around the entrance pupil and focusing is done by changing bellows draw.
There is a Bracketeer for Windows.
http://www.milosparipovic.com/dslr-bracketeer.html
I have it installed on my PC with XP Pro and it works like a charm.
http://www.milosparipovic.com/dslr-bracketeer.html
I have it installed on my PC with XP Pro and it works like a charm.
Did some stacks with the canon 100mm macro lens and a few ones with this lens and a Raynox DCR-250 in front of it, I think the result is good until the 2x magnification, with the raynox and good until 1:1 with the lens "naked".
After testing automated software I prefered the total control using the Canon EOS utility, there is better histogram control and with this approach I could use smaller apertures at the end of the stack, making a more natural sense of DOF.
I think this technique is sub-par for magnifications above this (with the actual solutions), the high mag work people anchieve with microscope objectives is better at high magnifications.
I wonder how a infinity objective would work in front of the 100mm macro lens being used with the autofocus motor step, I'm also wonder how a infinity objective would work using for a tube some entry level lens like Canon Ef-s 55-250mm or 55-200 mm f/4.5-5.6 (the last one with already tested good results but using a mechanical stage) these lenses extend while focusing (the 100mm macro don't) and I'm not sure if the changes in working distance could compromisse the focusing steps.
Possibly the use of a 180mm macro lens with a infinity microspope objective (200mm) is a viable alternative for high mag use of the live view, but who has this gear to post a test ?
After testing automated software I prefered the total control using the Canon EOS utility, there is better histogram control and with this approach I could use smaller apertures at the end of the stack, making a more natural sense of DOF.
I think this technique is sub-par for magnifications above this (with the actual solutions), the high mag work people anchieve with microscope objectives is better at high magnifications.
I wonder how a infinity objective would work in front of the 100mm macro lens being used with the autofocus motor step, I'm also wonder how a infinity objective would work using for a tube some entry level lens like Canon Ef-s 55-250mm or 55-200 mm f/4.5-5.6 (the last one with already tested good results but using a mechanical stage) these lenses extend while focusing (the 100mm macro don't) and I'm not sure if the changes in working distance could compromisse the focusing steps.
Possibly the use of a 180mm macro lens with a infinity microspope objective (200mm) is a viable alternative for high mag use of the live view, but who has this gear to post a test ?