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Different versions of Fujinon-TV 75/1.8
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PostPosted: Wed Jun 03, 2015 7:12 pm    Post subject: Different versions of Fujinon-TV 75/1.8 Reply with quote
Previously I was only aware of a single variant of this lens, the CF75A. Here is an eBay listing for example.

Somewhat miraculously I've now also managed to turn up a data sheet for this lens (I've never been able to find specifications). Unfortunately for me it is in Japanese. Here is what Google Translate makes of it.

The reason I started digging is because today this eBay listing came in the mail. That's an entirely different-looking lens, also 75/1.8, called HF75SA-1. On the same Fuji website I found its data sheet (google translation) as well. And I also found a data sheet (translation) for a third version, called CF75HA-1.

I am now filled with more questions than answers.

What is the difference between these?

Do they differ in their optical, or only mechanical aspects?

What do the letters in the code names stand for?

HF75SA-1 is listed as compatible with 1/3", 1/2", and 2/3" type lenses, while the other two also support 1". But it is alleged that in practice, the CF75A covers APS-C. Am I to assume that HF75SA-1 does not?

The "back focus" is listed differently for CF75A (31.71mm) than for the other two (24.43mm). What does this mean? Is that the same thing we know as register or flange focal distance? But the distance for C-mount lenses is supposed to be 17.5mm. So this is probably something different. But what?

What's listed as "Recent imaging range at the time of contact" in the translation is also different for CF75A than the other two (which are equal for same-sized sensors). What the heck is this?

The length of some extent of the lenses is described by diagrams, but I find it a little difficult to decipher. From where to where do these measurements extend? (Ideally, I'd like to know it from the mount to the lens' end.)

Does anyone know Japanese?

(At least the mass is unambiguous.)


PostPosted: Wed Jun 03, 2015 10:33 pm    Post subject: Reply with quote
The other two are CS lenses. C-Mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-Mount lenses Wink


PostPosted: Wed Jun 03, 2015 11:43 pm    Post subject: Reply with quote
May I politely ask what you're basing this judgment upon? Do you have direct knowledge from some source (perhaps experience)?

It may be that there's some obvious clue which I'm not picking up on, but my untrained eye sees nothing to suggest such a conclusion. CF75A indeed has a 17.526 distance specified in its diagram. And it's also specified as "C Mount". But the other two have no distance specified that I can see, are also listed as "C" mount, and the 12.5mm figure appears nowhere. Not even the difference between the specified back focus distances is a match (17.526 - 12.5 = 5.026 vs. 31.71 - 24.43 = 7.28).


PostPosted: Thu Jun 04, 2015 6:32 am    Post subject: Reply with quote
Probably these datasheets help:

http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/HF50_75HA-1B_04.pdf
http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/HF50_75SA-1_03.pdf
http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/CF50_75HA-1_03.pdf

All three lenses with C-mount.
Back focal distance is the distance between last lens and image (at infinity setting).


PostPosted: Thu Jun 04, 2015 7:27 am    Post subject: Reply with quote
I have had three copies of this lens and they all covered APS-C.


PostPosted: Thu Jun 04, 2015 10:07 am    Post subject: Reply with quote
ZoneV wrote:
Probably these datasheets help:

http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/HF50_75HA-1B_04.pdf
http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/HF50_75SA-1_03.pdf
http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/CF50_75HA-1_03.pdf

All three lenses with C-mount.
Back focal distance is the distance between last lens and image (at infinity setting).


Aha, very much! Thank you. This answers some of the questions. Apparently the "recent imaging range at time of contact" seems like something related to maximum magnification

The back focus distance for the others is all greater than the C-mount register distance, except for HF75HA-1B (15.74mm) - I wonder if this suggests that this one is actually a CS-mount lens? The alternative would be that the rearmost lens extends into the mount - which is not unheard of (Biogons), but would be odd (especially for a 75mm lens for a small sensor). Either way, this is clearly a different lens from the others, max. aperture, back focus, mass, dimensions etc. are all very different.

On the other hand, the specs (and appearance) of HF75SA-1 and CF75HA-1 is virtually identical. There is a 5g difference in mass, and Fujifilm has specced one of them for 1" type 5MP sensors, and the other only for 2/3" type 1.5MP sensors. But everything else is exactly the same. So it seems highly likely that these are actually the same optical design and there's just some labelling difference for market segmentation purposes (perhaps the difference is between better and worse copies of the same lens).

That does also make it seem likely that the CF75A is a different design - back focus, exit pupil, and magnification are different. As far as I know most tests with mirrorless cameras have been with CF75A, so I wonder how the other two would perform (and how large a sensor they actually cover).


iangreenhalgh1 wrote:
I have had three copies of this lens and they all covered APS-C.


Three copies of the same model, or of different ones?


PostPosted: Thu Jun 04, 2015 10:54 am    Post subject: Reply with quote
glaebhoerl wrote:
..
The back focus distance for the others is all greater than the C-mount register distance, except for HF75HA-1B (15.74mm) - I wonder if this suggests that this one is actually a CS-mount lens? The alternative would be that the rearmost lens extends into the mount - which is not unheard of (Biogons), but would be odd (especially for a 75mm lens for a small sensor).
..

The rear lens of the other two lenses is behind the flange part. Here not. See at the lens diagramm on the right side.
All C-Mount.

glaebhoerl wrote:
..
On the other hand, the specs (and appearance) of HF75SA-1 and CF75HA-1 is virtually identical. There is a 5g difference in mass, and Fujifilm has specced one of them for 1" type 5MP sensors, and the other only for 2/3" type 1.5MP sensors. But everything else is exactly the same. So it seems highly likely that these are actually the same optical design and there's just some labelling difference for market segmentation purposes (perhaps the difference is between better and worse copies of the same lens).
...


Probably both lenses have the same optical setup, but the 5 Megapixel lens has a lens with adjustment, for example centering, and this allows to use more field and better quality. This would explain the 5g difference.
Or thy sort the lenses, and the better ones are sold as 5 Meagpixel lenses. Today such lens sorting could be done automatical for cheap smartphone lenses.


PostPosted: Thu Jun 04, 2015 5:58 pm    Post subject: Reply with quote
There is only one optical design and it is a Biotar type. There are quite a few Fujinon C and H code lenses that are actually identical. One example being the CF25HA and HF25HA, same lens, different barrel.


PostPosted: Thu Jun 04, 2015 9:25 pm    Post subject: Reply with quote
Well it actually looks like all the mentioned are real C-mounts. I just assumed they where CS mount (same mount with different register distance which are quite common on newer CCTV lenses) and I am sorry for that. But I still doubt that these other lenses can be adapted to a still image camera because of the design. The rear of the lens is probably to wide.


PostPosted: Fri Jun 05, 2015 5:27 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
There is only one optical design and it is a Biotar type. There are quite a few Fujinon C and H code lenses that are actually identical. One example being the CF25HA and HF25HA, same lens, different barrel.


This is useful information, thank you. But in this instance it seems unlikely for CF75A to be the same design as the others - it has a different back focus and exit pupil distance e.g. I don't think that would be possible with the same optics? If that's true then there are at least two 75/1.8 Fujinon-TV designs.


PostPosted: Fri Jun 05, 2015 8:02 pm    Post subject: Reply with quote
There re only few basic designs, with many modifications. So the Petzval lens is sometimes modified to a a lens with more than 4 lenses. Some very fast lenses are Petzval based, but still very different to the pure old Petzval.
The same with triplet lenses, some give soap bubble background bokeh, other not.
A Double Gauss could be symmetrical, or very unsymmetrical to get more free space for the mirror od (D)SLR cameras. Lens design is much more than choosing the lens type!
The lens design tye can for example be found with the Quioptiq Preddesigner tool.

I have spend some hours on learning lens design simplest basics.
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