camera focus constant, move camera... or use focus ring?

Shooting in macro mode, techniques, tips & tricks

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okie

camera focus constant, move camera... or use focus ring?

Unread postby okie » 09.05.2008 20:29

Both instances seem to work well: The camera lens-focus distance maintained, thereafter move the camera itself forward, or, keep the camera-location fixed and create layers by different lens focus points.

Question: are there specific situations where one method is better than the other? I use a sturdy 7" slider-rail (RRS equipment) so either choice is applicable.

An aside: Initial test shoots seem to suggest f/8 is a best-choice, compared to f/5.6 or wider; likewise better than f/11 or 16. Lens is a 100mm Canon macro on a Canon 5D.
I also achieve outstanding results using Canon's 400mm f/5.6 telephoto lens with two or three extension tubes added. Image wise I'm inclined to suggest the 400mm combination produces better visual results than the macro-specific built 100mm lens... but the latter is far easier to focus and manage.

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Dan Kozub
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Unread postby Dan Kozub » 12.05.2008 17:45

I think that moving the camera may introduce noticable distortions if you camera moves along some object. By moving the camera you are changing view point and angle between object.

Phil Indeblanc
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Unread postby Phil Indeblanc » 15.01.2009 04:20

How would this work with a camera such as the mamiya RZ ? The lens doesnt focus, the bellows does the focusing. What would you suggest to a fresh HF rookie to do using this setup?

thank you!
Phil

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Dan Kozub
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Unread postby Dan Kozub » 15.01.2009 09:41

how are you focusing then? : )

Try to move the camera with a focus set to manual. This is the way that many of our users prefer.

Phil Indeblanc
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Unread postby Phil Indeblanc » 15.01.2009 10:04

I think for the 35mm format user Okie, it would be easier for the software to align if you just use the focus ring.

I on the other hand, I am using a medium format RZ, so the back film plane is mounted on a tripod. I think I have to use my focus rail so I can slide the camera back and forth to focus differnt areas. But I have read that this introduces problems?

If I could get a lens collar wide enough to fit over the 140 RZ macro lens, I could have the back move so the plane isn't shifted, but I have not found such a collar. Any suggestions, as many MF focus in this manner, and would like to get the best results possible, aside from going to 4x5.

thanks
Phil

saltyone
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Re: camera focus constant, move camera... or use focus ring?

Unread postby saltyone » 12.12.2010 05:32

I am wondering if this thread has been resolved? iemove camera on a rail or just adjust focus, and why helicon recomend the Cognisys stack shot rail ? I am going to use a 60mm macro on a 7D and perhaps some extn rings.
Any reason I cant use a manual ziess lens?

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Stas Yatsenko
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Re: camera focus constant, move camera... or use focus ring?

Unread postby Stas Yatsenko » 13.12.2010 11:22

I have not heard any theoretical explanation which method is the best. From the practical point of view, it depends. Rails give more precise control. But a macro photographer which shoots at 5:1, reported us that macro rails require 4 secons pause after each movement to calm down the vibrations. That is why he prefers to change focus with the lens ring. I would recommend macrorails if you are not limited by time and DOF is very small (0.1mm or so)

botanicalmacroUK

Re: camera focus constant, move camera... or use focus ring?

Unread postby botanicalmacroUK » 25.08.2011 17:27

I am not a physicist but I do think that there must be some optical preference of one system over the other. I am not talking about mechanical preferences (vibration etc.) or cost, but just the optical geometry. In both methods there must be some 'parallax' change of any one single point being photographed, and its position on the sensor. This is automatically remapped by the algorithms of course. My question is whether the required remapping is significant between the two systems? And which requires the greater-moving the camera or lens focus adjustment? Or in actual practice do all the other parameters override any small pixel repositioning?
Thank you

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Stas Yatsenko
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Re: camera focus constant, move camera... or use focus ring?

Unread postby Stas Yatsenko » 29.08.2011 10:02

Helicon Focus aligns images before stacking, which means that is compesates maginification changes. But it cannot compensate relative shifts of object due to change of viewpoint. Charles Krebs in his article in this forum (viewtopic.php?t=1141) has written that entrance pupil of the lens should be kept constant in the ideal case. He was moving the camera back with lens completely fixed. If he is correct, you need to choose method which produces smaller shift of the entrance pupil of the lens. It depends greatly on construction of the lens.

jimshirey
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Re: camera focus constant, move camera... or use focus ring?

Unread postby jimshirey » 29.08.2011 21:52

i use the focus ring when shooting with a small aperture and move the camera/lens along my rrs rail when the lens is more open. that's because the open lens requires far more slices, which is hard to do with focus ring adjustments. both methods give good results. vibrations can be minimized by using live view, since it locks up the mirror. also, you can see when enough time has passed for handling vibrations to damp out. it also helps to tighten the set screw slightly. this keeps the camera from wobbling as it runs along the track.

Dik

Re: camera focus constant, move camera... or use focus ring?

Unread postby Dik » 07.09.2011 15:48

The lens should stay in a fixed position to eliminate all parallax errors.
I wish Stackshot would make a bellows system that has a tripod mount at the lens stage.
Then Helicon Focus could run the stack automatically, and there would be no parallax errors.

vlnarav
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Re: camera focus constant, move camera... or use focus ring?

Unread postby vlnarav » 09.10.2011 05:38

Hi, this is my first post here. I am using Helicon Focus and Helicon Remote with Stackshot Macro rail. So far the results seems very good. Here you can see some examples:

http://victor-naraveckis.smugmug.com/Flowers/Flowers-Helicon-Naraveckis/19175936_dq2Wz4#1494461441_TF64kmK-A-LB

http://victor-naraveckis.smugmug.com/Flowers/Flowers-Helicon-Naraveckis/19175936_dq2Wz4#1494462949_t7Jm3Nn

http://victor-naraveckis.smugmug.com/Animals/Insects-Naraveckis-Helicon/19176426_tXWp9B#1494525649_mRJwMV9-A-LB

Helicon Remote controls the Stackshot Macro rail very well and is very flexible in terms of parameters adjustments. Moving the camera with the Macro rail produces a bigger stack (more pictures) but I think the results are better.


CoffeeDog
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Re:

Unread postby CoffeeDog » 09.02.2012 07:16

Phil Indeblanc wrote:How would this work with a camera such as the mamiya RZ ? The lens doesnt focus, the bellows does the focusing. What would you suggest to a fresh HF rookie to do using this setup?

thank you!


Hi Phil. The Mamiya RZ, and all other bellows cameras, focus in the same way as any other camera. With an SLR lens the focusing mechanisms are hidden within a protective metal or plastic barrel and a bellows system has a simple cloth or flexible plastic housing. What is important is the distance from the image to the film plane or imaging chip. When focusing either type of camera the film plane remains stationary while lens elements move. This brings us to the crux of the thread topic.

What happens when the distance from the subject to the film plane changes along the same axis, as we are speaking of here, is that there is a change in perspective; some here have referred to this as parallax. I have not used Helicon Focus yet, in fact I have just downloaded it tonight to give it a spin, but I am willing to make a guess here. It seems that Helicon Focus searches for areas of the image that are in focus, perhaps looking for edge contrast. The program can have no way of understanding how the image appears (oh look, mountains that are in focus but that little flower is not) so it must examine each image in the stack in order to find areas that fit the parameters of a focused image. Since there is much more going on than a simple addition of layers, those parts of the image that is able to be replace by a different image in the stack are discarded. At its most basic it would seem that there would be some perspective errors resulting from the moving camera method but they may be very subtle, and perhaps they could be eliminated using corrective techniques similar to those found in lens aberration programs and anti-keystoning filters.

Ultimately there may be some geometric error introduced into the image that may be of some significance to one involved in macroscopic measurements when using rail system for focus stacking, but it seems unlikely that such errors would be of much consequence in other applications. There can also be intra-lens errors introduced when using the focus ring to change focus, such as a shift in the plane of focus and its incidence upon the film plane/image chip.

Regarding the best f-stop: such a choice is system dependent. Some lenses are best at one stop when used with a certain camera or imaging chip size but will have a different 'best' if the camera is changed or if a different chip size is used. This is one of those things where we have to test each lens on each camera we use to find what works best.

IgorDS
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Re: camera focus constant, move camera... or use focus ring?

Unread postby IgorDS » 24.05.2014 19:38

My analysis of the two situations:
1) Move the camera and lens together without changing the distance between the lens and camera (no focus ring change)
2) Change focus using the lens focus ring - move the lens with respect to the sensor/film position

In 1) the optical characteristics of the lens remain the same; while in 2) the optical characteristics of the lens could change (and will with many modern multi-element complex lens constructions).
Depending on your set-up you may prefer 2) due to ease of handling, lack of a rail with suitable travel, vibrations or some other factors; but optically 1) should be a better choice.


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