Olympus 100x Achromat versus Apochromat, added 20x and 40x

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Linden.g
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Olympus 100x Achromat versus Apochromat, added 20x and 40x

Post by Linden.g »

I've just obtained a set of Apo's to upgrade from my Achromats. This is a comparison of the Olympus 100x S-Plan Achromat (top) versus the 100x S-plan Apochromat using DIC flash and NFK 2.5x projection lens on a BH-2. No stopping down of the condenser diaphragm. Images are 50% crops with no sharpening. The sample is a kemp diatom test slide.

Image
Last edited by Linden.g on Thu Mar 28, 2013 2:08 pm, edited 2 times in total.

Charles Krebs
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Post by Charles Krebs »

There's no going back now :wink: :wink:

Wait 'til you compare the 20X :wink:

Linden.g
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Post by Linden.g »

Charles Krebs wrote:There's no going back now :wink: :wink:

Wait 'til you compare the 20X :wink:
You are right Charlie, there is no going back. You did say I'd appreciate the difference. This test really does show the Apo as being significantly better. I'm testing the rest of the set now. They all look optically really clean. However, I did have some concern with the 20x, when I look down the back of the lens it looks free of defects but the black front mask is worn and showing some transparancy at its edges. Is this probably going to reduce contrast performance of the objective?

Linden

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Post by ChrisR »

Beginner's question (- I don't look at thing like this!)
Would you typically stack something like this? I can see excess colors, but if they're longitudinal CA they'd go, to a large extent, yes?
Are the NA's (very) different on these two objectives?

Linden.g
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Post by Linden.g »

ChrisR wrote:Beginner's question (- I don't look at thing like this!)
Would you typically stack something like this? I can see excess colors, but if they're longitudinal CA they'd go, to a large extent, yes?
Are the NA's (very) different on these two objectives?
Hi Chris, the S-plan Achro has a NA of 1.25, the Apo is 1.30. Yes I would typically stack for diatoms like this. This is a single image, as is, out of the camera, apart for croping and centering the exposure. I'm not sure how much stacking would reduce the CA as I typically reduce the CA in post processing before stacking. I'm sure others more experinced will know.

Linden

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Post by Linden.g »

Here is the S-plan 20x Achro (NA 0.46) versus the Apo (NA 0.7) comparison. Considerable resolution differences and much reduced CA, as Charlie indicated. Not sure how typical the residual CA is in the Apo so would appreciate comments on that. Note this is a significant crop and is at least 1/5 the wide of the full frame.

Image

Here is the 40x comparison Achro (NA 0.7) Apo (NA 0.95), 1/3 crop

Image

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Post by Fredlab »

Hello

Congrats for your purchase.
You rocks with these objectives.

(one day, 40/0,95 will replace my SPlan 40/0,7)
I apologise for my poor english
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rhamvossen
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Post by rhamvossen »

Hi,

Yes, nice differences. On diatoms that is. It's a common misconception that a (plan) apo is a complete replacement for an ordinary achro. It is not. That, you will only realise after some experimenting with circular oblique illumination with a Heine condenser. Also darkfield can show you some clear advantages of an achro: less glare. I use apo's alongside achro' as they have both their benefits. In my opinion, there is definitely a way going back.

Rolf

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Post by Linden.g »

rhamvossen wrote:Hi,

Yes, nice differences. On diatoms that is. It's a common misconception that a (plan) apo is a complete replacement for an ordinary achro. It is not. That, you will only realise after some experimenting with circular oblique illumination with a Heine condenser. Also darkfield can show you some clear advantages of an achro: less glare. I use apo's alongside achro' as they have both their benefits. In my opinion, there is definitely a way going back.

Rolf
Hi Rolf, I agree and plan to keep both sets of lenses. The working distances alone in some cases is a sufficient reason. I often do reflected light work and I don't have an epi system so I need the working distance to get light on the subject. I haven't explored the darkfield differences yet but it will be interesting to see that effect.

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Post by Pau »

Nice tests (and congrats for your new lenses)
You confirm two well stablished points:
- Apos are better color corrected and a bit more contrastly than Achros
- The main difference in resolution is due to the NA

I think your Plan achro images are also very good and the main difference is as expected CA correction. But with the 20X 0.7 vs 0.46 makes a big difference. For the 40X the difference is surprising small, in fact I can't easily pick a winner from this images.

Rolf,
I've never found any optical advantage of achros over fluorites or apos, but I don't have a Heine condenser and I'm not an expert tester
Pau

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Post by curt0909 »

Great comparison and congrats on the new lenses. When I first started using apo's I was blown away with the increase in color, detail, contrast. Like Charlie said, there's no going back.

The only benefit I've found in achro's over fluors/apos is working distance and resilience to quality loss from using the incorrect cover glass. But fluors and apos come in long working distance varieties that will best the achros in every way.

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Post by rhamvossen »

Hi,

The mentioned better contrast of (plan) apo's is another misconception. Since an apochromat has way more lenses than an achro there will be more reflection and light scattering. Just compare a simple achromat and a (plan) achromat of the same age. The latter is important because you simply cannot compare an old achro with a more modern apo that has benefited from improved anti-reflection coatings and the like. Another factor is slide quality: for quick and dirty work achro's rule. Thicker slides can ruin the image from a high NA apo. There were fluorite objectives mentioned: these I definitely favor above apo's: they have fewer lenses than apo' s and are better corrected than achro' s: they are more or less the best of both worlds.

Rolf

curt0909
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Post by curt0909 »

rhamvossen wrote:Hi,

The mentioned better contrast of (plan) apo's is another misconception. Since an apochromat has way more lenses than an achro there will be more reflection and light scattering. Just compare a simple achromat and a (plan) achromat of the same age.
Regarding the better contrast of apos vs achros I don't believe it is a misconception. In practice I've found it to be true and quite noticeable. This test shows it is true with these particular Olympus objectives and the difference is great in favor of the apo. Even compared to fluorite objectives apos are noticeably better. Here is a recent comparison by another member with a fluor and apo.

http://www.photomacrography.net/forum/v ... ctive+test

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Post by Litonotus »

I compared CFI PA vs PF here: http://www.photomacrography.net/forum/v ... hp?t=19564

apo is better, that's obvious, but there are some disadvantages of those objectives:

- short WD
- inaccurate slide and coverglass thickness influence image
- specimen must be possibly thin

they are perfect for photomicrography but when it comes to work plan fluors may be the best choice between quality and ease of use.
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I'm looking for the the extemely rare V-IM magnification changer for the E800 scope. If you have seen a listing or have one for sale please let me know.

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Post by rhamvossen »

Here's a comparison I made a while ago. Left 2 pictures: Leitz Pl Apo 25/0.65. Right 2 pictures: Leitz achromat 25/0.55. Also visible is the reduced glare with the achro in Darkfield. One should also keep in mind that sharpness is something else than contrast.

Image

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