Advice regarding Objectives for photography

Paul K · Post by **Paul K** » Sat Nov 30, 2013 10:21 am

I was wondering if someone could steer me in the right direction regarding an objective or two for photography. I have a cone adapter and another adapter for the camera is just trying to figure out of the objectives below would do what I need them to do. Close up macro

Would these do the trick

http://pages.ebay.com/link/?nav=item.vi ... 0980612154

And

http://pages.ebay.com/link/?nav=item.vi ... 0980617726

The auction end in 2 hrs and you advice would be greatly appreciated.

rjlittlefield · Post by **rjlittlefield** » Sat Nov 30, 2013 11:15 am

Just looking at the pictures, it appears the working distance would be painfully short. I don't have any other information. The seller doesn't even show whether these are finite or infinite. I would pass.

You can get a "known good" new manufacture 4X NA 0.10 objective for about the same price. See Lenses for use at 4-5X on an APS-sized sensor. Then for finite, search eBay for "4x plan achromatic objective" and look for the ones that look like the Cnscope plan achro in that thread. For infinite, look lower in the same thread at the Nikon CFI BE. It's more expensive, but it's a very good lens.

A known good 10X will cost you more than the Meiji, but I'm quite sure you would not be pleased with the working distance of the Meiji.

I hope this helps.

--Rik

Paul K · Post by **Paul K** » Sun Dec 01, 2013 12:26 am

Thanks for the info Rik its appreciated and saved me £50

Needless to say I let them both go and didn't bid. I did ask the question of the were finite or infinite. The response from the seller lead me to post the question here.

Looking at the the 'Lenses for use' thread I see the objective mounted straight on to the lens. I have a Rodenstock Rodagon 50mm f2.8 reversed on to my 100mm f2.8 for close up stuff using step down adapters etc.

What type of adapter is used for mounting the Objective straight on to the lens?

I am finding it quite difficult to source a suitable 5x, and 10x Objective in the UK as there are so many too choose from which would appear to be a hit or a miss.

Again, and not wanting to take advantage of your god nature, and suggestions would be gratefully welcomed.

Rgds

Paul K

rjlittlefield · Post by **rjlittlefield** » Sun Dec 01, 2013 1:43 am

If you haven't already done so, please study the FAQ: How can I hook a microscope objective to my camera?.

I have a Rodenstock Rodagon 50mm f2.8 reversed on to my 100mm f2.8 for close up stuff using step down adapters etc.

That Rodagon 50mm stopped down to f/5 is almost the same as a 4X NA 0.10 infinity type microscope objective, just mounted in a different barrel.

If you stuck it on the front of a 200 mm rear lens, you'd be getting 4X, and that's exactly the way infinity 4X objectives are intended to be used.

I have not had hands-on experience with the Rodagon, but my guess is that the resolution you can get with it is very similar to what you would get from a typical inexpensive 4X or 5X objective.

What type of adapter is used for mounting the Objective straight on to the lens?

They're just screw thread adapters, as discussed in the FAQ thread. Depending on which objective you get, you'll be needing something like http://www.ebay.com/itm/Nikon-CFI-M25-m ... 0287554493 or http://www.ebay.com/itm/RMS-8-microscop ... 0750438193, plus a step ring to fit your lens if it's not 52mm filter thread.

But note that this applies only for infinity objectives, and when you're using infinity objectives the magnification that you get depends on the length of the rear lens. Most objectives give their specified magnification only when used with a 200 mm rear lens. If you stick them on 100 mm, then you'll only get half the rated magnification and you're liable to get coverage problems at the same time.

Finite objectives are generally designed to require 150 mm of empty separation between the focal plane and the mounting thread of the objective, which typically means about 100 mm of extension tubes.

Good finite 10X can be purchased new from Edmund Optics; see http://www.photomacrography.net/forum/v ... php?t=9393. In used objectives, the Nikon E Plan such as http://www.ebay.com/itm/Nikon-E-Plan-10 ... 0963749544 has good reports. There are others, less commonly available, but again be sure to ask.

For infinite 10X my favorite inexpensive objective is the Nikon CFI BE discussed at http://www.photomacrography.net/forum/v ... hp?t=16348. In the UK it can be obtained directly from Nikon but you may have to be persistent depending on exactly which representative you get hold of.

--Rik

ChrisR · Post by **ChrisR** » Sun Dec 01, 2013 6:51 am

I've not used a Rodagon 50mm F/2.8 "normal", only an "Apo" which is very good.
As it's an enlarger lens, it's not designed to work at infinity, but eg 3x or 4x is within its range (when reversed).
There's a distinct possiblility then that it would work better on tubes/bellows, than at infinity reversed on another lens. If you focus the 100mm lens closer, you push it even further out of range.
I've not made a comparison myself with an enlarger lens. Normal 50mm camera lenses ( some, certainly) are better reversed onto another lens, but they are designed to work at infinity.

Paul K · Post by **Paul K** » Sun Dec 01, 2013 12:13 pm

Rik, Chris,

Thanks for the response. Getting there now!

Just to clarify Rik if I stuck a Nikon CFI BE 4x objective on a Canon EF 100mm f2.8, I would be getting 2x mag, and also if the objective was a 10x it would be 5x mag or there abouts.

If I stuck it on a 200mm it would therefore give 4 and 10x mag, would that be correct?

rjlittlefield · Post by **rjlittlefield** » Sun Dec 01, 2013 12:28 pm

It seems that my late-night typing made me less careful than usual...

Chris makes a very good point about the issues of using a finite-corrected lens as if it were infinite, and vice versa. Each design really should be used its own proper way. My comments about the similarity between a microscope objective and the Rodagon were intended to tap into Paul's experience with the 50mm + 100mm combo, to explain what he'd be getting with a 4X infinity objective.

Given that Paul already has the Rodagon and a 100 mm rear lens, I'll suggest that one reasonable step is straight to a Nikon CFI BE 10X infinity objective. Paired with his 100 mm rear lens, the CFI BE 10X will deliver an actual 5X, and it will be stunningly sharp in comparison to the best that would ever come out of a 4X or 5X microscope objective. Again, see HERE. The main drawback is that the high sharpness inevitably comes with very shallow DOF, typically around 0.010 to 0.005 mm focus step.

Edited to add: Paul, yes, your interpretation is correct. I did most of my wordsmithing before you posted, so the flow seems a bit odd now.

--Rik

Paul K · Post by **Paul K** » Sun Dec 01, 2013 2:49 pm

I looked at that image Rik, and was wowed, by how sharp it was.

I use a NovoFlex Castel L for focus stacking. Given the increments you mentioned would that be possible or would I be looking at something like StackShot, or home made

ChrisR · Post by **ChrisR** » Sun Dec 01, 2013 5:07 pm

Nice Rail Paul but I think you're going to be struggling to make 5 micron steps

It's surprising how small a step you can make, if you engineer a bit of round cardboard or a plastic knob with a printed scale taped round it. 1/100th of a turn is certainly doable.

I'd agree about skipping the 4x objective, unless you like to play, for now. They're OK but rather inflexible compared with an enlarger lens, which also has the desirable adjustable diaphragm, on variable extension. For web images you can stop down to use fewer steps, and also close the diaphragm at the end of the stack for a more gentle sharp-focus falloff. The Enlarger lens will give you more working distance too, if you can live with that long extension.
A supplementary diaphragm is available for objectives, via M42. If you go for a 10x, to use as a 5x, I think you'd find a diaphragm useful.

If you don't want to use tubes/bellows with your enlarger lens, then it might be worth trying a standard 50mm camera lens reversed on your 100, if you have one. Any make of course. (Or, you can get eg a Zuiko etc for £20)
(Hmm, I feel a comparison test coming on..)

If you have an internally-focusing 100mm, then you can actually use that to do focus increments, to a point. Easier, if "tethered".

Paul K · Post by **Paul K** » Mon Dec 02, 2013 5:41 am

Thanks for the info Chris, is there another way round using a 5x objective in micron steps other than StackShot. Having a look on the forum I have seen other members adaptations which are way above my current experience, and knowledge.

I don't mind doing manual stacks of 150 images as long as there is a precise increment step, and if it is possible to have a scale or micrometer to do so, I would rather go that way and save up for StackShot in the not too distant future.

Paul K · Post by **Paul K** » Mon Dec 02, 2013 10:28 am

I have an XY stage which came with no instruction manual. As I am just starting out on my adventure, could anyone else tell me what the scale refers to on the stage

rjlittlefield · Post by **rjlittlefield** » Mon Dec 02, 2013 10:47 am

Paul K wrote:I have an XY stage which came with no instruction manual. As I am just starting out on my adventure, could anyone else tell me what the scale refers to on the stage

It's a position indicator. What you're showing are two vernier scales, one in inches and the other in mm. See http://en.wikipedia.org/wiki/Vernier_scale for discussion about how to read them.

The current position of your scales is not a normal operating position. Normally the 0 mark of the short scales would lie within the 0-to-max range of the long scales.

--Rik

rjlittlefield · Post by **rjlittlefield** » Mon Dec 02, 2013 10:56 am

I am intrigued to see that there appears to be a labeling error on the vernier for the inch scale. Where it says "1/12inch", it should actually say "1/128inch". This is because the long scale has tick marks at 1/16 inch, which the vernier subdivides into 8 smaller divisions each: 16*8 = 128.

My recommendation is to just ignore the inch scale and use the mm one. It's far simpler anyway.

--Rik

Paul K · Post by **Paul K** » Mon Dec 02, 2013 11:09 am

Thanks Rik,

Here is what I'm thinking, but due to inexperience I'm not sure.

With the 10x objective mounted on the 100mm and the subject on the XY Stage, rather than move the camera towards the subject move the subject towards the camera, using the mm scale.

Would that work on terms of being close to micron focus ad Chris R spoke shout in the previous posts

I suppose I am looking for an alternative to StackShot, as funds are very low at the moment

rjlittlefield · Post by **rjlittlefield** » Mon Dec 02, 2013 11:50 am

Paul K wrote:Would that work on terms of being close to micron focus

Probably not. The finest scale reading on that stage is 0.1 mm, which is 100 microns. You can check for yourself, but I'm guessing the linear movement is in the range of 15-40 mm per turn of the dials, depending on which axis you choose. Even at 15 mm per turn, the 1/100 turn that Chris mentions becomes 0.15 mm = 150 microns.

The basic problem is that the drive mechanisms on those stages are just rack and pinion with no other step-down mechanism. To work in the micron range, you really need either a screw drive or some sort of reduction gearing.

I suppose I am looking for an alternative to StackShot, as funds are very low at the moment

Sure. There are several options, depending on your DIY inclinations and skills and/or how much time & enthusiasm you have for shopping eBay and waiting for good stuff to pop up.

For pretty low budget and short lead time without much DIY, I suggest considering a Proxxon KT-70 table such as shown in John Hallméns setup HERE. That provides a 1 mm per turn screw, which is adequate up to NA 0.25 with 5 micron steps if you add a bigger handle and work carefully (1/200 turn per step).

If you're much more into DIY, then you can get similar fine movements with a simple sliding stage driven by say an M6x1 threaded rod from your local hardware store. See HERE and later contributions in the same thread by Soldevilla.

--Rik