Some General Questions From an Eager Newbie

Just bought that first macro lens? Post here to get helpful feedback and answers to any questions you might have.

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cshahar
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Some General Questions From an Eager Newbie

Post by cshahar »

Hi:

I have some general questions before I dive into the fascinating world of photomacrography. Three days ago I did not even know such a word existed! To make matters worse, I am a bit technically challenged. However, I do have experience as an astrophotographer which might come in handy (lack of vibration during exposure was also a concern, and I also had to stack images).

OK: I want to take extreme closeups of insects. I have a Sigma SD14 DSLR (using Foveon technology). I also have a 105mm Macro lens (APS equivalent=158mm).

I want to marry this lens to a microscope objective. I am thinking a Nikon 10x NA 0.25. Is my 105mm lens long enough to accommodate this microscope objective? Or do I need an extension tube to provide a further 50mm? For some reason, I am under the impression that I need a total of about 200mm between the sensor and the objective to avoid vignetting, but I could be wrong.

The filter thread on the 105mm is 58mm. What is the thread on the microscope objective so that I could get an adapter to marry the two? What is this adapter called?

My camera does not have live view. Is this a big problem? It does have a mirror lock up, however.

I want to get a StackShot and universal remote for automatic focusing and image taking (I used to guide on stars manually for hours when I took pictures of nebulae and almost had to be locked up as a result). Assuming I get the StackShot, I was wondering what platform to rig this thing up to: I like the idea of a vertical copy stand, or perhaps the Novoflex macro stand.

Please let me know if there are any significant gaps in my thinking!

Thanks a bunch,

-Charles

henke
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Post by henke »

Hello,

I have recently bought the microscope objective that you are considering. While I do not have much experience in the area of photomacrography, I think I can answer some of your questions as I have asked them myself.

The lens has a 25 mm thread, and a good adapter is available by JinFinance on eBay:
http://cgi.ebay.com/Nikon-CFI-M25-micro ... 0287554493

That adapter brings it up to 52mm, if you add a 58 mm to 52 mm step-down ring, you will be good to go. Step down rings should be available at any respectable camera accessory vendor, but is also available at the previously mentioned eBay vendor.

There are a few reports of the lens working well at 105 mm. Personally I have tested it on an old 105mm f/4 Micro-Nikkor without vignetting issues. However, I have only received my adapter earlier today, and haven't had time to make overly thorough tests yet. On a 105mm lens you will get approximately 5.25x magnification, not the specified 10x which is only obtained when attached to a 200mm lens.

The lack of LiveView will make the setup phase a bit more difficult since the feature is quite useful for initial alignment and focus prior to stacking, but shouldn't be a dealbreaker otherwise I believe.

--
Henrik

cshahar
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Joined: Wed Jun 15, 2011 6:54 pm
Location: Montreal

Post by cshahar »

Henke, thank you so much for the reply! I also have a 50-200mm Sigma lens, but it is very heavy (I am worried about flexure) and I am not sure how sharp it is at the high end. If I use the 105mm, how can I increase magnification? Should I add an extension tube? May I ask, where did you buy the microscope objective? Was it online? What are you using as a rig for the whole assembly?

Thanks!

-Charles

Craig Gerard
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Post by Craig Gerard »

Charles wrote:Assuming I get the StackShot, I was wondering what platform to rig this thing up to: I like the idea of a vertical copy stand, or perhaps the Novoflex macro stand.
Charles,

What are your intentions regarding the StackShot? It can be setup using various methods for in-the-field application or in a studio environment. It can also be used in a vertical or horizontal configeration.

There are many threads in this forum discussing the StackShot. Here is one example:
http://www.photomacrography.net/forum/v ... php?t=9547


Craig
Last edited by Craig Gerard on Thu Jun 16, 2011 7:13 pm, edited 1 time in total.
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

cshahar
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Location: Montreal

Post by cshahar »

Hi Craig: I much prefer a studio environment for the first few months. I would have much more control in that set up. Which is better in terms of setting up for insect shots, vertical or horizontal? I really can't picture it yet as I have not tried it.

Thanks,

-Charles

Craig Gerard
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Location: Australia

Post by Craig Gerard »

Charles,

Our posts crossed paths. I added a link to my initial response.

If you do a search of the forum for "stackshot" related posts you will find considerable information, not all will be relevant to your requirements but it will provide a good first look at some of the ways members are using the StackShot.

I've used the StackShot attached to a vertical copy stand. It can be used to move the camera or used separately to move the subject. The Stackshot is also quite at home on a sturdy tripod equipped with an Arca clamp.


Craig
Last edited by Craig Gerard on Thu Jun 16, 2011 7:23 pm, edited 1 time in total.
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

rjlittlefield
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Post by rjlittlefield »

Charles, welcome aboard!

Adding to what Henrik has already said...

Using the 105 mm focused at infinity will give accurately 5.25X (=10*105/200). Focusing the 105 mm closer than infinity will increase the magnification, but will simultaneously add aberrations that degrade the image quality. Adding extension tubes carries this process to an extreme. I'm guessing you wouldn't like what it does to the image, but if you already have tubes it would be worth a try.

It's better to increase magnification by using a longer telephoto or equivalently, by putting a TC behind the tube lens to make it act longer while still leaving the stuff behind the microscope objective focused at infinity.

The quality of the telephoto lens is generally not very important in this application because the small aperture of the microscope objective effectively stops down the system. With the 10X NA 0.25 on your 105 mm, you will be running at f/10.5 effective. Put it on the 200 mm, and the combination will be effectively f/20.

Nikon CFI Plan Achromat 10X NA 0.25 objectives like shown HERE are commonly available on eBay from vendor automationseconds. One is posted right now, item 160604819015 at $155 buy-it-now price.
...under the impression that I need a total of about 200mm between the sensor and the objective to avoid vignetting...
This is not quite correct, but there is enough truth to be confusing. Let me explain...

There are two different aspects to vignetting.

One of them is that the microscope objective covers only about a 5 mm field of high quality image. If you push the magnification too low by using a short tube lens, you may run into this limit, but on your sensor you'll still be OK at 105 mm from this aspect.

The other aspect is corners going dark because the aperture of the objective and the aperture of the telephoto lens fight with each other. This happens when the aperture of the telephoto lens (more properly the "entrance pupil") is too small or too far back. This is most likely to occur with a zoom telephoto that is set to be shorter than its maximum focal length. Zoom telephotos set to maximum length and non-zoom telephotos usually work OK. In all cases you should leave the telephoto's aperture wide open. Stopping it down will not improve image quality but may cause vignetting.
Which is better in terms of setting up for insect shots, vertical or horizontal?
It depends on what you want to do. My bench setup can go either way and generally I end up using it horizontal because it's easier and safer to adjust that way. (I am more worried about dropping lenses etc when the rig is vertical.) The StackShot can also be used on a tilting tripod head to give an adjustable angle when that's helpful. See for example HERE and HERE

--Rik

cshahar
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Post by cshahar »

Thanks Criag. Very useful thread. I need to study it in more detail. The rigs all look very sturdy. Many rely on people's mechanical skills to build. Unfortunately, I am not that savvy when it comes to mechanics but I will have to figure something out. I understand the importance of having a rigid system!

-Charles

cshahar
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Location: Montreal

Post by cshahar »

Rik, fantastic! Thank you so much for the information. Can you explain to me what the advantages of using a reversed lens is? For instance, a 50mm? Is it used in combination with the microscope objective or with other lenses?

Also, can you expand any more on the lack of a live view in the camera and its implications for doing this type of photography? Would it help if I got a magnifier for the rangefinder to do initial focusing?

Thanks!

-Charles

rjlittlefield
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Post by rjlittlefield »

cshahar wrote:Can you explain to me what the advantages of using a reversed lens is? For instance, a 50mm? Is it used in combination with the microscope objective or with other lenses?
The main purpose of reversing a lens is to improve image quality. Every lens works best when the two focus planes have some specific relationship to the lens. For example the normal lens of a DSLR is designed to work when one focus plane is close to the rear of the lens (where the sensor normally sits) and the other focus plane is far in front of the lens (where a landscape would be). If you combine that lens with long extension or the equivalent so as to put the lens very close to the subject, then you have to reverse the lens so that the subject is close to what's normally the rear of the lens. Otherwise the image quality drops dramatically.

Reversed lenses are commonly used at the end of bellows extension or in front of a long lens that also essentially provides a lot of extension. For example if you reverse a 50 mm lens in front of a 200 mm lens, then you get 4X magnification on sensor (4=200/50).

Reversed lenses are not normally used in combination with microscope objectives. I could contrive a situation where it would be appropriate, but I've never encountered one in normal practice.
Also, can you expand any more on the lack of a live view in the camera and its implications for doing this type of photography? Would it help if I got a magnifier for the rangefinder to do initial focusing?
Given that you already have the Sigma, it's no big deal. Everything you need to do can be done by looking through the eyepiece.

A magnifier per se probably won't help much, but an angle finder can be very helpful because a lot of setups make it difficult to get your head in position for a direct view.

If you were starting from scratch, then without hesitation I would recommend to get one of the newer Canon DSLRs that provide Live View and electronic first shutter curtain (EFSC). EFSC essentially eliminates camera vibration as a cause of unsharpness, so in quiet environments it allows using continuous illumination even at high magnification. With other cameras that have only mechanical first shutter curtain, you have to use flash at high magnification to freeze the motion that is almost inevitably introduced by the shock of shutter opening. Canon's Live View implementation also plays well with the StackShot's use of external shutter release. (I've been told that certain Nikon's require a lot of mode switching to make it work.)

Or if you were needing to demonstrate your system to other people, especially in group situation, then I would strongly recommend some form of Live View. There's nothing quite so immediately understandable as to put a Live View image on a big monitor and press the FWD and BACK buttons on the StackShot controller while saying "As you can see, DOF is vanishingly shallow at this magnification. The way we're going to work around that problem is..."

A final advantage of Live View to a computer is that it allows seeing what the camera sees on the same screen as previously grabbed images, and on the same screen that shows the StackShot controls if you're using the computer for that. I use these features quite a lot in setting up comparative lens tests.

However, the benefits of EFSC, group presentation, and computer screen display are certainly not enough to warrant buying a different camera unless you get extraordinarily serious about this macro stuff.

Your main problems at this stage of the game will be mastering optics, lighting, and specimen prep. Most of what you do with the camera will be framing and establishing start/end points for the stack. Those functions can be done very nicely through the eyepiece. Some people prefer to do it that way even when Live View is available.

Hope this helps...

--Rik

cshahar
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Post by cshahar »

Please see next message. This one doesn't apply any more. Thanks!
Last edited by cshahar on Fri Jun 17, 2011 8:52 am, edited 1 time in total.

cshahar
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Location: Montreal

Post by cshahar »

I am definitely going to buy a Canon body, for three reasons: live view, electronic first shutter curtain, and compatibility with the stackshot. I think the Sigmas are too deficient in features to work well in this case.

My question now: Does it matter if I get the 40D or a cheaper Rebel??

Sorry about all these questions, but if I am to spend significant moneys, I need to get expert advice. Thanks!

-Charles
Last edited by cshahar on Fri Jun 17, 2011 9:16 am, edited 2 times in total.

Pau
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Post by Pau »

cshahar wrote:.... I am definitely going to buy a Canon body, for three reasons: live view, electronic first shutter curtain, and compatibility with the stackshot.
but don't buy the, otherwise nice, 60D:

http://www.photomacrography.net/forum/v ... highlight=
Pau

ChrisLilley
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Post by ChrisLilley »

cshahar wrote: OK: I want to take extreme closeups of insects. I have a Sigma SD14 DSLR (using Foveon technology). I also have a 105mm Macro lens (APS equivalent=158mm).

I want to marry this lens to a microscope objective. I am thinking a Nikon 10x NA 0.25. Is my 105mm lens long enough to accommodate this microscope objective?
Probably, at it would give you around 5x magnification.
cshahar wrote: Or do I need an extension tube to provide a further 50mm? For some reason, I am under the impression that I need a total of about 200mm between the sensor and the objective to avoid vignetting, but I could be wrong.
You have part of it right.

A 105mm lens on 50mm of extension tubes is not the same as a 155mm lens.
Calling multiplying the focal length by the crop factor and then adding 50 does not get you a 200mm lens, either.
A 200mm lens would give the rated 10x magnification with the objective you mentioned.

Adding extension is a common technique for focusing closer - the minimum focus distance decreases and so does the maximum focus distance (i.e. it becomes shorter than infinity).

However, these 'infinity' objectives are designed for a tube lens focused at infinity. So adding extension just takes the objective away from its design point
cshahar wrote:The filter thread on the 105mm is 58mm. What is the thread on the microscope objective so that I could get an adapter to marry the two? What is this adapter called?
Its 25mm. There is an M25 t M52 adapter available, and you would use a 58-52mm step-down ring to join this with your lens.
cshahar wrote:My camera does not have live view. Is this a big problem? It does have a mirror lock up, however.
Live view is convenient but test shots are free and instant, so no, live view is not required.
Mirror lockup is certainly handy to have, especially with continuous illumination.

rjlittlefield
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Post by rjlittlefield »

cshahar wrote:My question now: Does it matter if I get the 40D or a cheaper Rebel??
I use a Rebel T1i (500D), purchased about 18 months ago because at the time it was the cheapest way to get good quality video capture also. This has been my main stacking camera since then. Works well; I'm not aware of any significant drawbacks.

Which Rebel were you looking at?

--Rik

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