PlanF objectives
Posted: Fri Jun 24, 2022 1:15 am
I have done a little more sleuthing into the PlanF objectives that are around various places. I also have done some testing on them , so can report a little on their performance.
One of the things that is a bit of a mystery is that there are both PlanF and Plan Fluor objectives coming out of China. To complicate matters, there are also PlanF and semi-apo objectives coming out of India.
In this little piece I will deal only with the PlanF and in comparison to one another and other objectives as a yardstick. I tested both the Chinese PlanF 40X .75 and the Indian PlanF 40X .75 against a Reichert Planachro 40X .66 and a Reichert Planfluor 40X .70. in the same stand using a set wide field eyepieces that perfectly corrected for the PlanF objectives (Olympus 180mm reference length format) and another set that perfectly corrected for the Reichert objectives. There is a very slight difference between the Olympus and Reichert systems.
The Reichert objectives are fairly typical for their types giving very well corrected images with excellent resolution. The 40X .70 planfluor in fact punches well above it's weight, with imaging that rivals a planapo and as well seeming to have a higher N.A. than it does. It has a good working distance allowing for haemocytometer use.
The two PlanF objectives are similar but not the same.
The Chinese version has larger diameter front and rear lenses and a wider optical tube when looking through the objective. It has a removable chrome shroud with painted data. The front lens is concave. The rear diaphragm is a threaded in knurled disc.
The Indian PlanF has an almost identical chrome barrel but with lightly engraved data. It doesn't seem to have a removeable shroud, although it just might be tight. It too has a concave front lens.The rear diaphragm is a threaded
in metal disc removeable with a pin wrench.
From a distance the two objectives look almost identical.
Performance
----------------------- Both of the PlanF objectives perform a cut above a planachromat. They are clearly not just a Planachro rebadged or a strain free version of a planachro. Do they perform like a planfluorite though : the criteria of which would be higher resolution, truer colours, better colour correction, better contrast and of course complete planarity? Normally too, they should have a shorter w.d. than the Reichert Planachro, which is about as good as most modern good quality Planachros
Well, yes and no. The Chinese PlanF resolves about as good as the Reichert Planachro but has a slight edge when it comes to colour correction. It is just ever so slightly not an achromat. Contrast is about the same and colour rendition is maybe slightly superior. Planarity is full with a flat field.
Given the smaller diameter lenses of the Indian PlanF, I expected it to be outperformed by the Chinese version but I was pleasantly surprised when it bore comparison to the Reichert Planfluor , rather than the Planachro. Although the Reichert is clearly superior in all ways, the Indian PlanF is obviously not in the Planachro league anymore. In comparison to the Chinese PlanF all measurement criteria are better with the resolution about midway between it and the Reichert Planfluor.
An odd thing about both the PlanFs is that they both have a much greater working distance than either of the Reichert objectives.
One lacking aspect of oriental objectives in general is that they are usually pretty sketchy when it comes to parcentering and I am sorry to say that both the PlanFs are no exception..
So. In short, if you can land a deal on one of these and I would endorse the Indian version, and you have a system and eyepieces they can work in, especially to ensure planarity and edge to edge colour correction : not too bad, especially the Indian version.
I will try to post some pictures later, if I get a chance.
One of the things that is a bit of a mystery is that there are both PlanF and Plan Fluor objectives coming out of China. To complicate matters, there are also PlanF and semi-apo objectives coming out of India.
In this little piece I will deal only with the PlanF and in comparison to one another and other objectives as a yardstick. I tested both the Chinese PlanF 40X .75 and the Indian PlanF 40X .75 against a Reichert Planachro 40X .66 and a Reichert Planfluor 40X .70. in the same stand using a set wide field eyepieces that perfectly corrected for the PlanF objectives (Olympus 180mm reference length format) and another set that perfectly corrected for the Reichert objectives. There is a very slight difference between the Olympus and Reichert systems.
The Reichert objectives are fairly typical for their types giving very well corrected images with excellent resolution. The 40X .70 planfluor in fact punches well above it's weight, with imaging that rivals a planapo and as well seeming to have a higher N.A. than it does. It has a good working distance allowing for haemocytometer use.
The two PlanF objectives are similar but not the same.
The Chinese version has larger diameter front and rear lenses and a wider optical tube when looking through the objective. It has a removable chrome shroud with painted data. The front lens is concave. The rear diaphragm is a threaded in knurled disc.
The Indian PlanF has an almost identical chrome barrel but with lightly engraved data. It doesn't seem to have a removeable shroud, although it just might be tight. It too has a concave front lens.The rear diaphragm is a threaded
in metal disc removeable with a pin wrench.
From a distance the two objectives look almost identical.
Performance
----------------------- Both of the PlanF objectives perform a cut above a planachromat. They are clearly not just a Planachro rebadged or a strain free version of a planachro. Do they perform like a planfluorite though : the criteria of which would be higher resolution, truer colours, better colour correction, better contrast and of course complete planarity? Normally too, they should have a shorter w.d. than the Reichert Planachro, which is about as good as most modern good quality Planachros
Well, yes and no. The Chinese PlanF resolves about as good as the Reichert Planachro but has a slight edge when it comes to colour correction. It is just ever so slightly not an achromat. Contrast is about the same and colour rendition is maybe slightly superior. Planarity is full with a flat field.
Given the smaller diameter lenses of the Indian PlanF, I expected it to be outperformed by the Chinese version but I was pleasantly surprised when it bore comparison to the Reichert Planfluor , rather than the Planachro. Although the Reichert is clearly superior in all ways, the Indian PlanF is obviously not in the Planachro league anymore. In comparison to the Chinese PlanF all measurement criteria are better with the resolution about midway between it and the Reichert Planfluor.
An odd thing about both the PlanFs is that they both have a much greater working distance than either of the Reichert objectives.
One lacking aspect of oriental objectives in general is that they are usually pretty sketchy when it comes to parcentering and I am sorry to say that both the PlanFs are no exception..
So. In short, if you can land a deal on one of these and I would endorse the Indian version, and you have a system and eyepieces they can work in, especially to ensure planarity and edge to edge colour correction : not too bad, especially the Indian version.
I will try to post some pictures later, if I get a chance.