think I may have found something.
http://tinyurl.com/khlgzce
linear XYZ stage, obviating the need for a focusing rail. The one concern I have is that it says it has a 5lb load capacity (which is fine: the combined weight of my lens, camera body, and tripod head is about 4.2 lb, which leaves a margin for any connecting adaptors), but it says it has a vertical load capacity of 2.5 lb.
Also the dimensions are small (about an inch by an inch), so I'm hoping I can mount a manfrotto 410 tripod head on it.
Will do some more investigating. Also learned a new term today: backlash, which limits how precise such instruments are.
macro for a very specific purpose - need advice on equipment
Moderators: Chris S., Pau, Beatsy, rjlittlefield, ChrisR
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rjlittlefield
- Site Admin
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There are much larger XYZ stages available also, with higher load capacities and in some cases lower prices.
See for example http://www.ebay.com/itm/XYZ-60X60mm-hor ... 1363806622.
--Rik
See for example http://www.ebay.com/itm/XYZ-60X60mm-hor ... 1363806622.
--Rik
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spacediver
- Posts: 16
- Joined: Thu Feb 05, 2015 1:53 am
I've decided to stick with one axis of motion (along the focal axis).
I'm thinking of going with the following stage:
http://search.newport.com/?x1=sku&q1=423
There are some good deals on the bay for this model.
I do, however, need some advice on getting a bottom bracket and a clamp, so that I can mount my Canon EOS 450D on the stage. Does anyone have any suggestions? I'd like to go with Arca Swiss, but I'm finding it confusing figuring out exactly what parts I need.
I'm thinking of going with the following stage:
http://search.newport.com/?x1=sku&q1=423
There are some good deals on the bay for this model.
I do, however, need some advice on getting a bottom bracket and a clamp, so that I can mount my Canon EOS 450D on the stage. Does anyone have any suggestions? I'd like to go with Arca Swiss, but I'm finding it confusing figuring out exactly what parts I need.
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TheLostVertex
- Posts: 320
- Joined: Thu Sep 22, 2011 9:55 am
- Location: Florida
You can make a plate for one with the appropriate holes for the stage and clamp(I did this for my parker slide), or you can buy a premade plate. Something like THIS
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spacediver
- Posts: 16
- Joined: Thu Feb 05, 2015 1:53 am
Thanks Vertex,
I have no idea how to even begin making a plate. I know how to use a screwdriver and hammer and that's about it, so I think going the premade route is for me :p
Just to be clear, I need three things right?
Plate
Bottom Bracket
Clamp
I don't really understand what a plate and clamp is. I understand that the bottom bracket is a fixture that you attach to the bottom of your camera, and it allows you to (somehow) interface with the clamp. Does the clamp interface with the plate?
How would I ensure that the bottom bracket I get is compatible with that particular plate? Wouldn't the width of the bottom bracket have to exactly match the width of the plate? And what about the clamp?
I have no idea how to even begin making a plate. I know how to use a screwdriver and hammer and that's about it, so I think going the premade route is for me :p
Just to be clear, I need three things right?
Plate
Bottom Bracket
Clamp
I don't really understand what a plate and clamp is. I understand that the bottom bracket is a fixture that you attach to the bottom of your camera, and it allows you to (somehow) interface with the clamp. Does the clamp interface with the plate?
How would I ensure that the bottom bracket I get is compatible with that particular plate? Wouldn't the width of the bottom bracket have to exactly match the width of the plate? And what about the clamp?
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spacediver
- Posts: 16
- Joined: Thu Feb 05, 2015 1:53 am
thought I'd share an update on my progress. Chris S. was incredibly helpful with guiding me towards the right equipment, and it works incredibly well now that everything is assembled and set up!
Here is the basic setup. It took a fair amount of experimentation to get it to the point where I could actuate the linear stage with minimal vibration, but I'm very satisfied with how well it works (btw in these photos, the display looks very washed out - this is not the case in reality
)
The adaptor and clamp are both hejnar photo, and the camera bracket is a cheap one off ebay that seems to work perfectly.
The first order of business is to establish a baseline performance of the camera. To do this, I ordered a ronchi ruling, which is basically a high quailty optical target that consists of a square wave grating. For my needs, it serves two purposes:
1: allows me to measure the modulation transfer function of the camera.
2: allows me to measure units of distance in the focal plane. The ruling is 10 line pairs per mm, so I can easily convert pixels to microns once I have acquired a focused image.
Here is an image of the ronchi ruling in action. I have it taped to the display surface (it's transparent, so the light of the CRT conveniently illuminates the ruling).
Also shown is the Canon EOS utility that is extremely useful for this sort of stuff. You can see a zoomed in live view of the ruling. Very handy for focus adjustments.
By taking images of the ruling when it is at a slight angle, I can obtain the modulation transfer function of the camera, and importantly, I can do so at different apertures. This will allow me to find the aperture that is the sweet spot between lens aberration and diffraction.
For anyone interested in modulation transfer functions, and the slanted edge method, see this excellent document by Douglas Kerr:
http://dougkerr.net/Pumpkin/articles/MTF_Slant_Edge.pdf
I'm halfway through it, and it's by far the most readable tutorial on this technique that I've found.
Initial measurements indicate each RAW pixel corresponds to about 1.3 microns. Once I subsample the images to extract trichromatic values (of which, luminance is the most important to me), this will increase to 2.6 microns per pixel.
Still lots to do, but making steady progress, and thanks to everyone who's helped out.
Here is the basic setup. It took a fair amount of experimentation to get it to the point where I could actuate the linear stage with minimal vibration, but I'm very satisfied with how well it works (btw in these photos, the display looks very washed out - this is not the case in reality
)The adaptor and clamp are both hejnar photo, and the camera bracket is a cheap one off ebay that seems to work perfectly.
The first order of business is to establish a baseline performance of the camera. To do this, I ordered a ronchi ruling, which is basically a high quailty optical target that consists of a square wave grating. For my needs, it serves two purposes:
1: allows me to measure the modulation transfer function of the camera.
2: allows me to measure units of distance in the focal plane. The ruling is 10 line pairs per mm, so I can easily convert pixels to microns once I have acquired a focused image.
Here is an image of the ronchi ruling in action. I have it taped to the display surface (it's transparent, so the light of the CRT conveniently illuminates the ruling).
Also shown is the Canon EOS utility that is extremely useful for this sort of stuff. You can see a zoomed in live view of the ruling. Very handy for focus adjustments.
By taking images of the ruling when it is at a slight angle, I can obtain the modulation transfer function of the camera, and importantly, I can do so at different apertures. This will allow me to find the aperture that is the sweet spot between lens aberration and diffraction.
For anyone interested in modulation transfer functions, and the slanted edge method, see this excellent document by Douglas Kerr:
http://dougkerr.net/Pumpkin/articles/MTF_Slant_Edge.pdf
I'm halfway through it, and it's by far the most readable tutorial on this technique that I've found.
Initial measurements indicate each RAW pixel corresponds to about 1.3 microns. Once I subsample the images to extract trichromatic values (of which, luminance is the most important to me), this will increase to 2.6 microns per pixel.
Still lots to do, but making steady progress, and thanks to everyone who's helped out.
Marwan, thanks for posting this follow-up! Nice to see pictures of what we concocted in our off-line communication. I'm glad to hear it's working well.
For other members of the forum, Marwan has a particular research interest in high-end CRT screens. He needed a photographic setup that facilitated these studies, on a limited budget. So his setup is low-tech (though sturdy) in elements where his use doesn't require anything fancy, and higher tech in the aspects that matter in his work.
His setup boils down to a stack of bricks (books could be used), with a translation stage for focus stacking placed on top. Also, an Arca-style camera plate and clamp to make using it convenient. All in all, not a multi-tasker, but a very cost efficient, robust mono-tasker well-suited to Marwan's research.
Cheers, Marwan! Again, thanks for the update.
--Chris
For other members of the forum, Marwan has a particular research interest in high-end CRT screens. He needed a photographic setup that facilitated these studies, on a limited budget. So his setup is low-tech (though sturdy) in elements where his use doesn't require anything fancy, and higher tech in the aspects that matter in his work.
His setup boils down to a stack of bricks (books could be used), with a translation stage for focus stacking placed on top. Also, an Arca-style camera plate and clamp to make using it convenient. All in all, not a multi-tasker, but a very cost efficient, robust mono-tasker well-suited to Marwan's research.
Cheers, Marwan! Again, thanks for the update.
--Chris
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spacediver
- Posts: 16
- Joined: Thu Feb 05, 2015 1:53 am
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spacediver
- Posts: 16
- Joined: Thu Feb 05, 2015 1:53 am
I've made quite a bit of progress on this project. Here's one of the updates:
Something that some of you may find interesting is that I've developed a method of taking the guesswork out achieving "perfect" focus (relative to the depth plane that one is interested in imaging).
Basically, I'm analyzing the live view image from the canon EOS utility in real time so I can quantify how focused the image is.
I use boxcutter to take a cropped snapshot of a zoomed in live view image. ( ). This takes a snapshot every second, and updates a file in a specified directory. I then use Matlab to analyze that image in real time, using the slant edge method. The value that I pay attention to is the standard deviation of the edge spread function. The lower this value, the sharper the image is. I adjust the micrometer until I get the lowest reading possible. The cropped image is an 87x253 image taken from the center of the sensor (which itself is 4290 x 2856).
Here's what the setup looks like:
The bright area is a lightbox, to which is taped the ronchi ruling (invisible due to bright light).
Here are the results of a couple experiments that I did to test the sensitivity and noise of my equipment.
First experiment: I set up the camera to image the ronchi ruling, and took 20 measurements at 20 different subject distances, each of which was separated by 10 microns (total of 400 measurements).
Here are the data. Error bars are standard errors of the mean (n = 20).
I hid the first few data points as there was some noise at the beginning. Note that the angle of the slanted edge was almost 7 degrees. If I had used a steeper angle (say 2 degrees), I'd get more precision due to increase in the supersampling factor. But even with that edge angle, the image processing is clearly able to distinguish subject distances of 10 microns.
Next, I wanted to see the results using single micron adjustments. This is tricky with my setup, as I needed to use the vernier scale, which was in an awkward position and hard to see clearly.
Here are the data from 17 subject distances (each of which has 20 measurements). The first few measurements were smooth, as were the last few, but in the middle I had to make a few readjustments, and the data seem to reflect this, although I think around peak focus, the rate at which focus changes is at a minimum, so that might be why the data is flatter there.
This data is impressive considering it's being generated from 8 bit image data. Ideally I'd be able to take the 14 bit RAW images and automatically process them real-time in the same way, them but that would a tedious challenge (for one thing, the fastest I can take images with the camera is once every five seconds), and I'm not sure it's worth it in my case, given the high precision I've already been able to obtain. This method is far far more precise than using my eye alone to judge the live view image.
I do have a question. Is the live view a solid indicator of the focus that would be achieved when taking an actual picture? I know the mirror flips out of the way when using live view, but I'm not sure what happens after that. Is there a secondary image sensor in the camera that generates the live view image? If so, if the light has to travel a different distance to get to this secondary sensor, relative to the distance it travels to get to the main sensor, then my method is useless if the difference in this distance is more than a micron.
Something that some of you may find interesting is that I've developed a method of taking the guesswork out achieving "perfect" focus (relative to the depth plane that one is interested in imaging).
Basically, I'm analyzing the live view image from the canon EOS utility in real time so I can quantify how focused the image is.
I use boxcutter to take a cropped snapshot of a zoomed in live view image. ( ). This takes a snapshot every second, and updates a file in a specified directory. I then use Matlab to analyze that image in real time, using the slant edge method. The value that I pay attention to is the standard deviation of the edge spread function. The lower this value, the sharper the image is. I adjust the micrometer until I get the lowest reading possible. The cropped image is an 87x253 image taken from the center of the sensor (which itself is 4290 x 2856).
Here's what the setup looks like:
The bright area is a lightbox, to which is taped the ronchi ruling (invisible due to bright light).
Here are the results of a couple experiments that I did to test the sensitivity and noise of my equipment.
First experiment: I set up the camera to image the ronchi ruling, and took 20 measurements at 20 different subject distances, each of which was separated by 10 microns (total of 400 measurements).
Here are the data. Error bars are standard errors of the mean (n = 20).
I hid the first few data points as there was some noise at the beginning. Note that the angle of the slanted edge was almost 7 degrees. If I had used a steeper angle (say 2 degrees), I'd get more precision due to increase in the supersampling factor. But even with that edge angle, the image processing is clearly able to distinguish subject distances of 10 microns.
Next, I wanted to see the results using single micron adjustments. This is tricky with my setup, as I needed to use the vernier scale, which was in an awkward position and hard to see clearly.
Here are the data from 17 subject distances (each of which has 20 measurements). The first few measurements were smooth, as were the last few, but in the middle I had to make a few readjustments, and the data seem to reflect this, although I think around peak focus, the rate at which focus changes is at a minimum, so that might be why the data is flatter there.
This data is impressive considering it's being generated from 8 bit image data. Ideally I'd be able to take the 14 bit RAW images and automatically process them real-time in the same way, them but that would a tedious challenge (for one thing, the fastest I can take images with the camera is once every five seconds), and I'm not sure it's worth it in my case, given the high precision I've already been able to obtain. This method is far far more precise than using my eye alone to judge the live view image.
I do have a question. Is the live view a solid indicator of the focus that would be achieved when taking an actual picture? I know the mirror flips out of the way when using live view, but I'm not sure what happens after that. Is there a secondary image sensor in the camera that generates the live view image? If so, if the light has to travel a different distance to get to this secondary sensor, relative to the distance it travels to get to the main sensor, then my method is useless if the difference in this distance is more than a micron.
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Charles Krebs
- Posts: 5865
- Joined: Tue Aug 01, 2006 8:02 pm
- Location: Issaquah, WA USA
- Contact:
The only SLR cameras I am aware of that used a second sensor for display only were some of the Sony models (A-350, A-380, A-390 and perhaps others). All other current DSLRs that I am aware of use the "taking" sensor for the live-view display.I know the mirror flips out of the way when using live view, but I'm not sure what happens after that. Is there a secondary image sensor in the camera that generates the live view image? If so, if the light has to travel a different distance to get to this secondary sensor, relative to the distance it travels to get to the main sensor, then my method is useless if the difference in this distance is more than a micron.
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spacediver
- Posts: 16
- Joined: Thu Feb 05, 2015 1:53 am
ah that's great to hear, saves me the hassle of double checking the correspondence between live view focus and focus in the RAW file.Charles Krebs wrote: The only SLR cameras I am aware of that used a second sensor for display only were some of the Sony models (A-350, A-380, A-390 and perhaps others). All other current DSLRs that I am aware of use the "taking" sensor for the live-view display.
thanks