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Interesting lens reflection
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PostPosted: Sun Jan 07, 2024 4:27 pm    Post subject: Interesting lens reflection Reply with quote

Look at this reflection I provoked when shooting straight into the sun with my MIR 24H 35mm f/2, you can literally see the aperture blades reflecting on the sensor.

Mir24Haperture212 by devoscasper, on Flickr

Furthermore I noticed this lens is really very sharp from wide open in the center, in fact so sharp it hardly improves when stopping down. The corners however, never seem to get really sharp, so not my first choice for landscape photography. EDIT: wrong! The MIR is actually very good in this regard: http://forum.mflenses.com/mir-24h-mc-35mm-f-2-vs-minolta-md-35mm-f-2-8-t84937.html

MFD is 24cm, which is very nice, and bokeh is quite nice as well. I will add some more images in the near future.


Last edited by caspert79 on Mon Jan 08, 2024 2:38 pm; edited 2 times in total


PostPosted: Sun Jan 07, 2024 5:23 pm    Post subject: Reply with quote

lol i guess landscape test you and Stevemark are doing is a torture for many lenses, wonder if this was ever intented to be used this way
definetely,these test are very educational and saving money for many of us, besides, not everyone is happy to show the weak sides of some lenses
i guess is the first time i see this kind of reflection on the image,probably on film would not apply same result
anyway, would like to see some bokeh shots of this lens, being so sharp in the center wide open, it would be a good bet for portraits and not only


PostPosted: Sun Jan 07, 2024 5:36 pm    Post subject: Reply with quote

kiddo wrote:
lol i guess landscape test you and Stevemark are doing is a torture for many lenses, wonder if this was ever intented to be used this way
definetely,these test are very educational and saving money for many of us, besides, not everyone is happy to show the weak sides of some lenses
i guess is the first time i see this kind of reflection on the image,probably on film would not apply same result
anyway, would like to see some bokeh shots of this lens, being so sharp in the center wide open, it would be a good bet for portraits and not only



Correct, this is probably not meant as a landscape lens. For other purposes than that, I expect the Mir to be pretty nice, and potentially better than other classic fast 35’s I have tried so far.


PostPosted: Sun Jan 07, 2024 6:56 pm    Post subject: Reply with quote

Interesting that the blades are casting a reflection of their own.
I don't think I've seen that before.
The only 35 f2 I have will exhibit angled flare rays with the light source well out of the image area. It's definitely an older lens.

Kind of curious about the condition of the blades in your lens, which isn't an informed question at all...

-D.S.


PostPosted: Sun Jan 07, 2024 7:08 pm    Post subject: Reply with quote

Not only an interesting reflection, but also an interesting lens section:



The rear half very much looks like an ordinary 1.4/50mm lens, and the front part seems to be deviated from the Zeiss Planar 2.8/80mm for the Hasselblad, which is slightly "wideangle" as well:

https://www.zeiss.ch/content/dam/consumer-products/downloads/historical-products/photography/hasselblad-cf/de/datasheet-zeiss-planar-2880-de.pdf

The Konica AR 1.8/40mm has a similar construction, too:
http://www.artaphot.ch/konica-ar/objektive/432-konica-hexanon-40mm-f18

S


PostPosted: Sun Jan 07, 2024 7:14 pm    Post subject: Reply with quote

Doc Sharptail wrote:
Interesting that the blades are casting a reflection of their own.
I don't think I've seen that before.
The only 35 f2 I have will exhibit angled flare rays with the light source well out of the image area. It's definitely an older lens.

Kind of curious about the condition of the blades in your lens, which isn't an informed question at all...

-D.S.


I haven’t owned many Russian lenses, but the ones I had didn’t have black aperture blades. I’m pretty sure the metal colored blades are the source of ‘the problem’.


PostPosted: Sun Jan 07, 2024 7:48 pm    Post subject: Reply with quote

@Stephan: thanks for your observations, very interesting.


PostPosted: Mon Jan 08, 2024 6:46 pm    Post subject: Reply with quote

caspert79 wrote:
Doc Sharptail wrote:
Interesting that the blades are casting a reflection of their own.
I don't think I've seen that before.
The only 35 f2 I have will exhibit angled flare rays with the light source well out of the image area. It's definitely an older lens.

Kind of curious about the condition of the blades in your lens, which isn't an informed question at all...

-D.S.


I haven’t owned many Russian lenses, but the ones I had didn’t have black aperture blades. I’m pretty sure the metal colored blades are the source of ‘the problem’.


i have few lenses with metal colored blades and i don´t recall having these results, it might have to do with glass type or coatings?
by the way, i´ve seen the results on landscapes compared to minolta, and to be honest, i didn´t expected to be on par closed down


PostPosted: Mon Jan 08, 2024 6:59 pm    Post subject: Reply with quote

Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


PostPosted: Mon Jan 08, 2024 7:02 pm    Post subject: Reply with quote

kiddo wrote:
caspert79 wrote:
Doc Sharptail wrote:
Interesting that the blades are casting a reflection of their own.
I don't think I've seen that before.
The only 35 f2 I have will exhibit angled flare rays with the light source well out of the image area. It's definitely an older lens.

Kind of curious about the condition of the blades in your lens, which isn't an informed question at all...

-D.S.


I haven’t owned many Russian lenses, but the ones I had didn’t have black aperture blades. I’m pretty sure the metal colored blades are the source of ‘the problem’.


i have few lenses with metal colored blades and i don´t recall having these results, it might have to do with glass type or coatings?
by the way, i´ve seen the results on landscapes compared to minolta, and to be honest, i didn´t expected to be on par closed down



Yeah, quite surprising.


PostPosted: Mon Jan 08, 2024 8:01 pm    Post subject: Reply with quote

Some of the optical signature of a lens, in terms of flare and other aspects, is also the result of things like sensor coating, and possibly camera mount geometry too, as well as filter design factors for things like colour shifts and corner resolution, not to mention the software choices made by that camera makers engineers. A second part of the puzzle is the construction of adapters, although lately the quality seems to be improved in many ways. I've often wanted to test certain lenses with different bodies from different manufacturers in controlled conditions to see if it could be quantified more fully, as this would also be worthwhile information to the average enthusiast. Unfortunately I don't have access to a second body myself and don't come across other enthusiasts in person.
There's a wealth of information about lens differences but surprisingly little about another quite important piece of the puzzle.


PostPosted: Mon Jan 08, 2024 8:20 pm    Post subject: Reply with quote

visualopsins wrote:
Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


Yeah, makes sense. The metal colored blades reflect light easily as well.


PostPosted: Mon Jan 08, 2024 10:24 pm    Post subject: Reply with quote

caspert79 wrote:
visualopsins wrote:
Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


Yeah, makes sense. The metal colored blades reflect light easily as well.


Or...the flare is simply lighting up the interior of the lens, adding to lens projection. In that case no sensor reflection; no diaphram blades reflection.


PostPosted: Tue Jan 09, 2024 5:32 am    Post subject: Reply with quote

visualopsins wrote:
caspert79 wrote:
visualopsins wrote:
Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


Yeah, makes sense. The metal colored blades reflect light easily as well.


Or...the flare is simply lighting up the interior of the lens, adding to lens projection. In that case no sensor reflection; no diaphram blades reflection.


If you look closely, you can see the shape of the individual aperture blades.


PostPosted: Tue Jan 09, 2024 6:04 am    Post subject: Reply with quote

caspert79 wrote:
visualopsins wrote:
caspert79 wrote:
visualopsins wrote:
Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


Yeah, makes sense. The metal colored blades reflect light easily as well.


Or...the flare is simply lighting up the interior of the lens, adding to lens projection. In that case no sensor reflection; no diaphram blades reflection.


If you look closely, you can see the shape of the individual aperture blades.


I see them clearly...

Suppose the lens has a front cap. A hole is drilled in the side of the lens body to place a lamp inside behind the aperture, thus lighting the interior of the lens behind the aperture, which we see in the image... The flare could be lighting up the interior of the lens behind the aperture...


PostPosted: Tue Jan 09, 2024 6:12 am    Post subject: Reply with quote

visualopsins wrote:
caspert79 wrote:
visualopsins wrote:
caspert79 wrote:
visualopsins wrote:
Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


Yeah, makes sense. The metal colored blades reflect light easily as well.


Or...the flare is simply lighting up the interior of the lens, adding to lens projection. In that case no sensor reflection; no diaphram blades reflection.


If you look closely, you can see the shape of the individual aperture blades.


I see them clearly...

Suppose the lens has a front cap. A hole is drilled in the side of the lens body to place a lamp inside behind the aperture, thus lighting the interior of the lens behind the aperture, which we see in the image... The flare could be lighting up the interior of the lens behind the aperture...


Now i see what you mean, yes it’s possible. The back of the aperture is lighted on way or the other.


PostPosted: Tue Jan 09, 2024 11:01 am    Post subject: Reply with quote

I would not be surprised if the aperture will reflect lights or there are light leaks at certain aperture value.

Here is a photo take from the rear of my own copy:


PostPosted: Tue Jan 09, 2024 11:33 am    Post subject: Reply with quote

caspert79 wrote:
visualopsins wrote:
caspert79 wrote:
visualopsins wrote:
caspert79 wrote:
visualopsins wrote:
Lens projection reflects off sensor back into the lens to reflect off diaphragm blades back out of Lens onto sensor. I've seen this with Tamron 2.5/90 macro, in addition to the well-known hot spot.


Yeah, makes sense. The metal colored blades reflect light easily as well.


Or...the flare is simply lighting up the interior of the lens, adding to lens projection. In that case no sensor reflection; no diaphram blades reflection.


If you look closely, you can see the shape of the individual aperture blades.


I see them clearly...

Suppose the lens has a front cap. A hole is drilled in the side of the lens body to place a lamp inside behind the aperture, thus lighting the interior of the lens behind the aperture, which we see in the image... The flare could be lighting up the interior of the lens behind the aperture...


Now i see what you mean, yes it’s possible. The back of the aperture is lighted on way or the other.


This is a problem with lenses with shiny reflective aperture blades.

It can be difficult to work out whether you are looking at the front or rear reflection of the aperture blades, and which lens surfaces are responsible for the "ghost" image (it's not really a "ghost image", but you know what I mean.)

In extreme contrast situations like this (dark lawn, sun near the centre of the frame), the residual internal reflections that lens designers would consider non-problematic for "normal" images, can become a problem. I would hazard a guess that caspert79 had a high dynamic range optimisation set in the camera, or lifted shadows quite a bit during post-processing, which exacerbates this kind of problem.

The fact that the surface structure and overlapping edges of the blades are sharply depicted suggests this is not a simple reflection of the rear of the aperture blades being imaged by the normal refractive properties of the rear cell, but rather additional reflections off internal lens surfaces are involved.

It is quite possible that this is a reflection off the front surface of the aperture blades bouncing back off the inner surface of one of the front cell elements, and that the reflection off the sensor surface is not involved here at all. In my experience, most strong specular sensor surface refections such as that of the sharp image of the sun in the frame show some form of colour banding/pattern in the ghost image(s) caused by sensor reflection, resulting from the colour filter in front of the sensor; this seems totally absent here.