Leica DM2500 condensers

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marwes
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Joined: Mon Oct 11, 2021 11:25 am

Leica DM2500 condensers

#1 Post by marwes » Mon Oct 11, 2021 5:42 pm

Hello everybody.
I have just bought Leica DM2500, nevertheless it doesn't meet all my expectations as they were specified ans accepted by Leica sales representative before the transaction.
A condenser I have (Pol Universal Condenser UCA/P) requires switching back a moveable head for objectives 5x and lower, so that without this head the whole FoV (25 mm) is seen but with lower image quality (for me it's unpleasant and unusable for routine diagnostic work), and with the head the image is better, smoother etc., but much smaller - and therefore unusable too.

There are a few condensers and a lot of their accesories you can use with DM2500 and I'm really confused with their specifications, potential differences in image quality and ergonomics. What more, Leica DM2500 vs DM2000 and DM3000 have meaningful differences regarding condensers.

Generally, in DM series you can have:

1. Standard condenser CLP/PH 0.85
2. CL/PH 0.90/1.25 OIL, color coding
2. Achr. apl. A 0.9 (P) and its automated version for DM3000
3. Universal condenser UCL 0.90/1.25 OIL
4. Pol Universal Condenser UCLP 0.85
5. Pol Universal Condenser UCA/P which can have dfferent replaceable achromatic heads: 0.90 S low strain, P 0.90 S1 extremely low-strain (for polarization), P 1.40 OIL S1 (for polarization and higher resolutions), 0.50 S15 low strain (for thicker glass, heating stages).

What are the differences between all those condensers and heads? (in terms of image quality, ergonomics, and keeping the full field of view with smooth look at low magnifications). As it is much more complicated in DM2500, Leica is going to let me try DM3000 for comparison, even though I chose DM2500 for its 100W illumination.

Can you use oil condensers together with dry lenses? Does polarization require "extremely low strain" head? And what does it exactly mean "low strain"? Does achromatic/aplanar condenser give better IQ than a conventional one?

Maybe it would be enough for now:) I will be extremely grateful for any help.

apochronaut
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Re: Leica DM2500 condensers

#2 Post by apochronaut » Mon Oct 11, 2021 6:38 pm

marwes wrote:
Mon Oct 11, 2021 5:42 pm
Hello everybody.
I have just bought Leica DM2500, nevertheless it doesn't meet all my expectations as they were specified ans accepted by Leica sales representative before the transaction.
A condenser I have (Pol Universal Condenser UCA/P) requires switching back a moveable head for objectives 5x and lower, so that without this head the whole FoV (25 mm) is seen but with lower image quality (for me it's unpleasant and unusable for routine diagnostic work), and with the head the image is better, smoother etc., but much smaller - and therefore unusable too.

There are a few condensers and a lot of their accesories you can use with DM2500 and I'm really confused with their specifications, potential differences in image quality and ergonomics. What more, Leica DM2500 vs DM2000 and DM3000 have meaningful differences regarding condensers.

Generally, in DM series you can have:

1. Standard condenser CLP/PH 0.85
2. CL/PH 0.90/1.25 OIL, color coding
2. Achr. apl. A 0.9 (P) and its automated version for DM3000
3. Universal condenser UCL 0.90/1.25 OIL
4. Pol Universal Condenser UCLP 0.85
5. Pol Universal Condenser UCA/P which can have dfferent replaceable achromatic heads: 0.90 S low strain, P 0.90 S1 extremely low-strain (for polarization), P 1.40 OIL S1 (for polarization and higher resolutions), 0.50 S15 low strain (for thicker glass,
1. CLP/ PH 0.85 A single diaphragm dry phase condenser intended for pol work. Phase diaphragms are replaceable by removal and insertion.
2. CL/PH 0.90/ OIL , colour coding. A single diaphragm dry (0.90) or oil immersion (1.25) condenser .
2. Achr./ Apl. A 0.9(P) and it's automated version for DM 3000. A .90 achr./apl. dry condenser for pol work , specific to the DM 3000
3. Universal Condenser UCL 0.90/1.25 OIL. A rotary disc or carousel condenser housing capable of holding 1 or more phase annuli, rotated in or out of the optical axis. The condenser lens section is used dry( 0.90) for phase and oiled (1.25) for other contrast systems.
4. POL Universal Condenser. UCLP 0.85. The same as above but with a dry 0.85 condenser lens section that is not ever oiled.
5. POL Universal Condenser UCA/P which can have different replaceable heads: 0.90 S low strain, P 0.90 S1 extremely low strain(for polarization), P 1.40 OIL S1( for polarization and higher resolutions), 0.50 S15 low strain( for thicker glass). A rotary universal type condenser that accepts different condenser lens sections depending on the application required.

A decision as to which condenser is the right one should be based on the application required not on testing condensers on the microscope. There are two sections to a condenser : the mechanical or diaphragm section and the optical or condenser section.
The choice of the mechanical section is based on convenience plus application. Leica offers a standard condenser and a universal condenser body. The standard body requires a little more fiddling with swapping phase diaphragms etc. The universal body allows for many components to be on board and changed simply by rotating the disc. If you are going to be including multiple phase objectives, the universal condenser body makes sense.
The choice of the optical( condenser section) is based on application. If you are not doing pol, then no pol ( extremely low strain S1) condensers are required. If you are not doing high resolution then oil immersion condensers are not required. If you are doing high resolution, then oil immersion is required and if you are using better colour corrected objectives, then ach./apl. may be required or even 1.40 N.A. achr./apl..

Oil immersion condensers can be used either dry or oiled and can be used in either mode with dry objectives. Usually lower N.A. dry objectives ( < .90) benefit from the condenser being used dry and objectives > .90 benefit from an oiled condenser. Unless the objective is over about 1.25 and oiled to the cover slip, dry condensers of .90 or greater provide very good imaging. If you are going to be using objectives with an N.A. of over 1.25 ( 1.30 to 1.40) , there is little advantage to a 1.40 high N.A. ach.apl. condenser.

Low strain refers to structural stress that remains in hardened liquids. In the case of lenses, this can occur both in the glass and in the cements that bond doublets and triplets together. Low strain or sometimes called strain free or S or SF lens systems are both designed to limit such stresses and tested to ensure it. Such stresses show up in polarization microscopy or any contrast technique that uses polarization, so low strain lens systems are required.

marwes
Posts: 9
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Re: Leica DM2500 condensers

#3 Post by marwes » Mon Oct 11, 2021 7:30 pm

Thank you very much!

My first application is cytology and histopathology which requires nothing more than brightfield (I often change between 5x and 10x and this is why I don't like removeable head!). Pathologists don't use other techniques and as far as I know are not familiar with them. BUT (last but not least): I want to develop my microscopic and microphotographic skills, so I'm going to use DF, POL, PH (in the future - I have no lenses for this yet), once maybe even more (DIC or fluorescence). I have also incident light axis in my Leica (only brightfield but that's amazing).

My lenses are fluorites (semiapo) with universal condenser 0.90 S (low strain) head. And everything should be good - but it isn't. Lens 5x is unusable (image is either small with a head or "unsoft" and unplesant without a head, e.g. in HE cytologic stain nucleated cells tend to get lost in bloody background). I'm curious what Leica is going to do with that but I'm pesimistic.

Regarding your answer, let me ask you more precisesly. Regarding polarization - does 0.90 S (low strain) is much worse than P 0.90 S1 (extremely low-strain) in this application? As I understand, P 0.90 S1 extremely low strain is not usable in applications other than polarization, including 'normal' brightfield?
And the last - does UCA/P heads (0.90 S, P 0.90 S1) are somewhat comparable, better, or worse than the one in achr. apl. condenser A 0.9 (P)? (as they also are achromatic but are they aplanatic too?).

Thank you again for your patience and time. Best regards!

PeteM
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Re: Leica DM2500 condensers

#4 Post by PeteM » Mon Oct 11, 2021 7:36 pm

Two thoughts about your dissatisfaction with the image at low magnifications, with your top condenser lens flipped out of position:

1) Low power images are often problematic since while the apparent depth of field is great the depth of focus is small. It can take extreme care to get decent photographic images -- and more pixels also required to resolve the detail. This might account for part of your frustration? In particular, the greater depth of field might be causing you to see more of the background "noise" than at higher magnifications?

2) The flip-top condensers are generally pretty good - but mainly meant as a convenient way of scanning a slide at low magnification with the top lens out and then flipping the top lens back in at higher resolution. Many makers (Nikon, Olympus, etc.) have a specialized low power condenser, which does about as best as can be done for numerical apertures up to, say, 0.30. I didn't see something like that that among those you listed.

DIC, with its optical sectioning is one possible solution, but very expensive. To its credit, Leica provides effective DIC prism options down to around the 4-5x range - many other makers only get down to about 10x.

PeteM
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Re: Leica DM2500 condensers

#5 Post by PeteM » Mon Oct 11, 2021 7:43 pm

To add, on your question about low or very low strain condenser lenses - I have the 0.90 S1 condenser flip top above a universal condenser on my Leica DMLB and it works well IMO for brightfield, polarization, and DIC. I wouldn't think you'd need anything better unless you were doing quantitative polarization work.

apochronaut
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Re: Leica DM2500 condensers

#6 Post by apochronaut » Mon Oct 11, 2021 11:14 pm

marwes wrote:
Mon Oct 11, 2021 7:30 pm


My lenses are fluorites (semiapo) with universal condenser 0.90 S (low strain) head. And everything should be good - but it isn't. Lens 5x is unusable (image is either small with a head or "unsoft" and unplesant without a head, e.g. in HE cytologic stain nucleated cells tend to get lost in bloody background). I'm curious what Leica is going to do with that but I'm pesimistic.
Your 5X performance sounds somewhat typical with a poorly suited or adjusted condenser. First, with the condenser top in the up position it is impossible for the condenser to provide a large enough circle of illumination , so flipping the high N.A. condenser lens down is required to achieve this. The 5X needs a condenser N.A. considerably lower than even that condenser provides with the top lens out of the way. Have you tried lowering the condenser a little on it's track and closing the iris diaphragm some?

apochronaut
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Re: Leica DM2500 condensers

#7 Post by apochronaut » Tue Oct 12, 2021 12:36 am

Another option is that most condenser systems have some way of putting decondensing lenses into the light path. Your condenser, even with the high N.A. back lens swung out of the light path , provides about 4 times the N.A. required by the objective.

marwes
Posts: 9
Joined: Mon Oct 11, 2021 11:25 am

Re: Leica DM2500 condensers

#8 Post by marwes » Sat Oct 16, 2021 6:06 pm

PeteM wrote:
Mon Oct 11, 2021 7:36 pm
1) Low power images are often problematic since while the apparent depth of field is great the depth of focus is small. It can take extreme care to get decent photographic images -- and more pixels also required to resolve the detail. This might account for part of your frustration? In particular, the greater depth of field might be causing you to see more of the background "noise" than at higher magnifications?
I'm not sure what is the difference between the depth of focus and depth of field but I think that at least one of them should be suspected ;) I think the deeper the depth of focus, the worse - the image is getting worse as the aperture diaphragm is getting smaller. But even at fully open aperture the image is bad.
PeteM wrote:
Mon Oct 11, 2021 7:36 pm
Two thoughts about your dissatisfaction with the image at low magnifications, with your top condenser lens flipped out of position:

2) The flip-top condensers are generally pretty good - but mainly meant as a convenient way of scanning a slide at low magnification with the top lens out and then flipping the top lens back in at higher resolution. Many makers (Nikon, Olympus, etc.) have a specialized low power condenser, which does about as best as can be done for numerical apertures up to, say, 0.30. I didn't see something like that that among those you listed.
Yes, I know, that's why I miss Olympus. It has such a great IQ with no need to move a condenser head. I hate that, so called, "scanning" or "screening" image quality, as low magnifications are of great importance (as well as 10x or 40x) in analizing histopathological slides.
Nevertheless, Leica has two solutions to this that I hadn't mentioned: 1) diffuser for low magnifications (not for POL) or 2) auxiliary lens for low magnifications (also for POL). The point is that only with automated condenser in DM3000 they automatically switch into the light path. My 'microscope dealer' has lent me DM3000 so that I can give it a try but unfortunately without those accessories (I'm not sure if they even were aware of them). But what good I can say about DM3000 - the automatization is great! Its disadvantage is weaker light (30W) than DM2500 (100W).

Thank you very much for your great answers.

marwes
Posts: 9
Joined: Mon Oct 11, 2021 11:25 am

Re: Leica DM2500 condensers

#9 Post by marwes » Sat Oct 16, 2021 6:31 pm

marwes wrote:
Mon Oct 11, 2021 7:30 pm
Have you tried lowering the condenser a little on it's track and closing the iris diaphragm some?
Yes, I have, but it doesn't work. It would be too impractical anyway.
apochronaut wrote:
Tue Oct 12, 2021 12:36 am
Another option is that most condenser systems have some way of putting decondensing lenses into the light path. Your condenser, even with the high N.A. back lens swung out of the light path , provides about 4 times the N.A. required by the objective.
I'm looking forward to test such solutions from Leica (they have offered mi neither a diffuser, nor an additional lens, despite they have such accessories in their catalogues!).

wabutter
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Re: Leica DM2500 condensers

#10 Post by wabutter » Sat Oct 16, 2021 9:21 pm

Relative to the comparison of 30w vs.100w Recall the intensity is proportional to the square of the distance the lamp is from the object. The 30w lamp is located right under condenser on the DM3000 while the DM2500 has the lamp house mounted on the rear of the scope, some inches away. It would be difficult to assess the difference in intensity with the naked eye unless you were working with very light demanding contrast methods.
The fundamental advantage of the 100w lamp would be the larger winding of the filament, there by filling the back aperture of the objective more fully than the the 30w. Resulting in a more homogeneous illumination of the object.

marwes
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Re: Leica DM2500 condensers

#11 Post by marwes » Sat Oct 16, 2021 9:59 pm

wabutter wrote:
Sat Oct 16, 2021 9:21 pm
Relative to the comparison of 30w vs.100w Recall the intensity is proportional to the square of the distance the lamp is from the object. The 30w lamp is located right under condenser on the DM3000 while the DM2500 has the lamp house mounted on the rear of the scope, some inches away. It would be difficult to assess the difference in intensity with the naked eye unless you were working with very light demanding contrast methods.
The fundamental advantage of the 100w lamp would be the larger winding of the filament, there by filling the back aperture of the objective more fully than the the 30w. Resulting in a more homogeneous illumination of the object.
Very interesting, I haven't thought about it from this point of view! What do you think about those differences in illumination power in the context of microphotography? Assuming use of contrast methods in light demanding conditions. Is it worth to take 100W over 30W, sacrifying ergonomics and automatization of DM3000?

microcosmos
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Re: Leica DM2500 condensers

#12 Post by microcosmos » Sun Oct 17, 2021 2:37 am

marwes wrote:
Sat Oct 16, 2021 9:59 pm
wabutter wrote:
Sat Oct 16, 2021 9:21 pm
Relative to the comparison of 30w vs.100w Recall the intensity is proportional to the square of the distance the lamp is from the object. The 30w lamp is located right under condenser on the DM3000 while the DM2500 has the lamp house mounted on the rear of the scope, some inches away. It would be difficult to assess the difference in intensity with the naked eye unless you were working with very light demanding contrast methods.
The fundamental advantage of the 100w lamp would be the larger winding of the filament, there by filling the back aperture of the objective more fully than the the 30w. Resulting in a more homogeneous illumination of the object.
Very interesting, I haven't thought about it from this point of view! What do you think about those differences in illumination power in the context of microphotography? Assuming use of contrast methods in light demanding conditions. Is it worth to take 100W over 30W, sacrifying ergonomics and automatization of DM3000?
My previous microscope (a Radical) had a 20W lamp without a reflector, right below the condenser. Brightness-wise it was ok with bright-field at low magnification. At high magnification it was dim, and with crossed polarizers I almost couldn't see. I tried sticking a flashlight reflector behind the lamp and it improved things a bit.

I would expect the 30W lamp in the DM3000 to be brighter than that, not only because of the higher power but also because I assume Leica (which generally designs microscopes well) has incorporated a reflector!

I now have a microscope with a 100W lamp, which is at the back of the scope. But I see a big difference in my case. At low magnifications it is much too bright to look through the eyepieces - I use ND filters to dim it (and swing them out for photography). At high magnifications things look very nice and bright even with crossed polarizers - I can see weak interference colours that were completely invisible under the 20W microscope.

However, the big difference I experienced could be partly due to the condenser. On the 20W instrument I had a condenser without a flip-up top lens, so it couldn't gather the already dim light more effectively for the high-powered objectives.

When taking photographs with 100W the shutter speed is about as fast as in normal photography. I guess it helps to have bright lighting if you have a moving plankton or if you're taking a video. It also helps when I am taking a large number of shots for focus stacking - the fast shutter speed saves a lot of time.

Everything else being equal, I'd go for the 100W. As wabutter wrote, the difference may not be massive although in light-demanding conditions any extra power would help.

Wabutter explained too that the 100W lamp fills the field of view more homogeneously - that would probably help too with the 25 mm FOV.

Is LED conversion an option? Being a purist I personally prefer halogen as it has a colour rendering index of 100, although I think good LEDs are really close and you can't really see the difference in normal use.

Are you within traveling distance of a Leica showroom? They should make demo instruments available for you to try out and compare the 100W and 30W (and fit your camera on them as well).

MicroBob
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Re: Leica DM2500 condensers

#13 Post by MicroBob » Sun Oct 17, 2021 5:03 am

I don' tknow the reason, but apparently it is more difficult than expected to get pefect illumination for objectives below 10x.
The resolution seems to be easier to acheive, but the colors tend to be wased out (in my stained plant sections, haven't tested carefully with histology slides).
Typical recommendations to illuminate a wide field are:
- Use base condenser lens
- Rack down
- Use auyillary lens
- use no condenser at all
- use a diffuser above the condenser
- use a low power condenser

I tested all but wasn't able to get as good an image as with higher powers, even when compared in a scaled down image. The differences were big, so experimenting is promising: You might try the diffuser (piece of tissue above condenser) as ir is quick to use.

Bob

microcosmos
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Re: Leica DM2500 condensers

#14 Post by microcosmos » Mon Oct 18, 2021 4:41 am

marwes wrote:
Sat Oct 16, 2021 9:59 pm
Very interesting, I haven't thought about it from this point of view! What do you think about those differences in illumination power in the context of microphotography? Assuming use of contrast methods in light demanding conditions. Is it worth to take 100W over 30W, sacrifying ergonomics and automatization of DM3000?
Sorry, I need to further qualify what I said earlier about 100W vs 30W. There is another factor I failed to mention. If you look at page 4 of this Nikon pol microscope brochure, it explains that 50W can be brighter than 100W if you use a mirror in the lamphouse to enlarge the light source. But I guess if you use a mirror on the 100W it will still be brighter - but maybe too bright for anything.

MichaelG.
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Re: Leica DM2500 condensers

#15 Post by MichaelG. » Mon Oct 18, 2021 6:57 am

marwes wrote:
Sat Oct 16, 2021 6:06 pm
I'm not sure what is the difference between the depth of focus and depth of field …
.
May I please refer you to my recent discussion with ‘linuxusr’
viewtopic.php?f=5&t=13415&hilit=depth+of+field

The difference is probably not intuitively obvious, but it is important to understand the distinction.

… Peter Evennett is my ‘go to’ source for such clarifications …

MichaelG.
Too many 'projects'

marwes
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Re: Leica DM2500 condensers

#16 Post by marwes » Sat Feb 19, 2022 12:55 pm

My problems with 5x magnification mostly have been solved by adding a diffuser from a higher model (DM6000) (it was put into the universal condenser to one of slots) but there is a price - it takes away a huge amount of light. However, I use this diffuser with all magnifications during my routine work and it's more or less ok.
Unfortunately I have some other troubles with my Leica DM2500. There is no acceptable parfocality between objectives (5x/10x, 10x/20x, only 20x/40x is right).
I don't understand what's wrong... The x/y coaxial drive is another crap as it doesn't work smoothly.
To summarise, I'm really disappointed with Leica and angry for how much money I spent on it :( . Never ever again Leica. Olympus has a much better quality-price ratio and is pleasant to work with while Leica makes me anxious and frustrated. Even changing objectives makes an awful metallic sound that hurts my ears.

Leicaman
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Re: Leica DM2500 condensers

#17 Post by Leicaman » Sun Jun 05, 2022 12:25 pm

marwes, could you share the part number of the diffuser you use for the low magnification? Is it also from Leica? I'm having similar issues, that is harsh/grainy illumination at 5x and below.

Also, I agree with your review on the DM2500. Any new DM microscopy is poorly made compared to the good old ones. I have also an old Leica DMRXP which is incomparably better built than any new DM.

fun fact: Did you know DM is short for Das Mikroskop?

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