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Want to know my lenses real speed.
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PostPosted: Tue Jun 21, 2022 9:16 am    Post subject: Reply with quote
[quote="europanorama"]yes thats true just came out from a test with zeiss 50/1.4 or 85/1.4- the f1.4 is at least 1/3- 1/2 stop darker clearly. in other words zeiss was cheating. will investigate further. one can also adjust light and change aperture. this way shutter-accuracy is not involved. best would be using film and resp. greyscale-card-and densitometer. i can then also check shutter-accuracy.
and digital cam shutter to be verified or tested the same way like with analog cam.
i compared f 1.4 to a f 1.5. f1.5 is about 1/3 darker.
yes i tested center with eye. its darker clearly. same discussion in a german forum.
just wanted to ask about the 135/1.8.
i have both CY 50/1.4 and Super Takumar 50/1.4 so i will compare asap.
.....................................................................................................
Which is darker for you. The CY 50 or the 85? I'm going to compare mine too.
Which 135/1,8 do you mean? The Sigma YS?
I did compare the 50 CY to the Takumar (the 8 elements with no yellowing. Therefore no loss of light) . That's when I started wondering about the differences.

In another thread I mention a 200mm f3,3 being quite darker than a 3,5. Let's just remember that if the real speed of any lens is important, we should test them. (except maybe the modern pro lenses?) Wink


PostPosted: Tue Jun 21, 2022 11:32 am    Post subject: Reply with quote
blotafton wrote:
..
So it seems to be true that the lens makers don't want to show the finer details.


I would not trust the optical diagrams too much. They don´t want to give too much details.

Thank you very much for that link, those patents and the linking to existing lenses is quite interessting - even when they are very likely not 100% accurate, they give an idea!


PostPosted: Tue Jun 21, 2022 12:23 pm    Post subject: Reply with quote
I have noticed that my C/Y Planar has warmer tones than other lenses. That means some of blue light is being blocked from passing through. That should reduce the T-stop.


PostPosted: Tue Jun 21, 2022 1:06 pm    Post subject: Reply with quote
[quote="Phalbert"]
europanorama wrote:
yes thats true just came out from a test with zeiss 50/1.4 or 85/1.4- the f1.4 is at least 1/3- 1/2 stop darker clearly. in other words zeiss was cheating. will investigate further. one can also adjust light and change aperture. this way shutter-accuracy is not involved. best would be using film and resp. greyscale-card-and densitometer. i can then also check shutter-accuracy.
and digital cam shutter to be verified or tested the same way like with analog cam.
i compared f 1.4 to a f 1.5. f1.5 is about 1/3 darker.
yes i tested center with eye. its darker clearly. same discussion in a german forum.
just wanted to ask about the 135/1.8/YS btw just tested sigma YS 16mm fisheye on eos 60D APS-C. its crap lot of CA and unsharp edges maybe only for SRL. made a lensshade from existing parts successfully!!!but sun most be outside image otherwise image is crap.

i have both CY 50/1.4 and Super Takumar 50/1.4 so i will compare asap.
.....................................................................................................
Which is darker for you. The CY 50 or the 85? I'm going to compare mine too.
Which 135/1,8 do you mean? The Sigma YS?
I did compare the 50 CY to the Takumar (the 8 elements with no yellowing. Therefore no loss of light) . That's when I started wondering about the differences.

In another thread I mention a 200mm f3,3 being quite darker than a 3,5. Let's just remember that if the real speed of any lens is important, we should test them. (except maybe the modern pro lenses?) Wink


PostPosted: Tue Jun 21, 2022 1:10 pm    Post subject: Reply with quote
i updated within old thread. sigma YS meant 135/1.8 discussed here.
i tested 85/1.4 quickly for aperture accuracy. must recheck didnt compare yet 50 and 85 regarding lightloss.
my subject outside window is most ideal to check center. also have 50/1.7. and ML counterpart.
soon i will have the sigma EX DC 10mm AF. 16mm equiv. on APS-C. will think about sunshade. its the one from mamiya for RB/RZ 80mm-lenstube to stick-on. Rafcamera made 82 and 77mm adapters for me. see his shop.
shade surface must be enlarged. mostly for FF. on crappy sigma 16 YS flare could be removed when sun is just outside image. it has a donot-like adapter for their lensshade. will test on SRL and decide if we need perfect adapter. donut-ring will further limit angle. maybe better using it for APS-C. will investigate further later. one can also hold this adapter/cam on tripod or make a swanneck for making adjustments for every shot. had to learn how this fisheye is built how frontlens is fixed. if not knowing and if manipulating lens one could encounter surprises.


PostPosted: Fri Apr 07, 2023 5:21 pm    Post subject: Reply with quote
blotafton wrote:
ZoneV wrote:
blotafton wrote:
...
I can also recommend looking at patents to see that the number printed on the lens is not always exactly the true values.

From Sonyalpharumors:
https://www.sonyalpharumors.com/new-sony-patents-discloses-details-about-the-new-135mm-f-1-8-and-100mm-f-1-4-fe-lenses/

The 135mm f1.8 is actually 131mm f1.85. But I'm not sure that is the final lens they ended up making but this is how it looks for most lenses.


As I work as optics designer a bit of warning: It is exolicit mentioned in at least in one of the lens design books I have read, ans alos heard this: The lens patents are deliberately NOT the real design of the lens. Perhaps this was different n the good old days of lens design, but today the companies dont give away the exact design they want to use with all refinment.


Not exactly the topic but there is a user on the dpreview forum that compares the schematics published by the lens makers with his own that I think he makes by inputting data from the patents into a design software to see varying degrees of accuracy. https://www.dpreview.com/forums/thread/4628869

So it seems to be true that the lens makers don't want to show the finer details.


Patents always show the first version. A sample may be another version. Production may have multiple versions. Which may mislead some to conclude to be hiding secrets, when in fact the secrets have evolved. Patents must be unique yet cover future versions.
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