[yusuf]

Which are the M lenses known for producing bad PF.

I know M85/2 is one, just wondering about other M lenses

[stevebrot]

Lenses don't produce purple fringing, it is a digital sensor issue. It simply does not happen with color film. That being said, some lenses are more prone to encouraging the sensor to fringe. I can offer two Pentax-M lenses that I own that don't seem to be associated with that problem.

M 50/1.7
M 200/4

Steve

FWIW...I only own a few lenses that cause my K10D to fringe at all. Care to guess which ones?

[wombat2go]

Hi Yusuf
Here is the offending lens SMC Pentax -M 1:2 85 mm you mention as being "bad PF" taking a shot wide open in the dark with bright lights !!, on aps-c , a pentax ist ds - no less !!

https://www.box.com/s/0ngldvkkw7w0relu0mh3

Here is your query for the lens on that shot in X
[root@localhost OlyRaw]# tca_correct -o cv *.jpg
here is the reply which you can feed to your gizmo whatever
-r 0.0000000:0.0000000:-0.0001282:1.0001706 -b 0.0000000:0.0000000:-0.0001529:1.0000598

Not too bad - Huh ??
You can post your "bad" image if you want ( needs 3000 pix across)

[Swift1]

Lenses don't produce purple fringing, it is a digital sensor issue. It simply does not happen with color film. That being said, some lenses are more prone to encouraging the sensor to fringe. I can offer two Pentax-M lenses that I own that don't seem to be associated with that problem.

M 50/1.7
M 200/4

Steve

FWIW...I only own a few lenses that cause my K10D to fringe at all. Care to guess which ones?

From my experience, fringing does happen on film. I imagine that major awareness of it didn't exist until pixel peeping though.
Here's a corner crop from a 2400 dpi scan of a Kodak Portra 400 VC negative shot with my SMC 6X7 45mm f/4 lens.


Unless this is somehow caused by scanning, I've definitely run across it a few times coming from this lens and different films.

[Jewelltrail]

I owned several M-series lenses & shot them on my K20d. As Steve says above, the 50 f/1.7 & 200 f/4 were no problem. However, the most fringing/CAs I"ve ever seen on digital were with the M 300 f/4. It was a beautifully built lens, & I had a mint copy, but could not deal with the fringing/CAs. If you used it selectively, excellent shots were possible.

JT

EDIT:My apology, I left Pentax a couple of years ago & all my efforts have been in Nikon ever since. I made a mistake---It was not the M 300 f/4 which was so poor--It was the K 300 f/4. My experience with the M 50 1.7 & 200 f/4 is accurate.

[maltfalc]

Lenses don't produce purple fringing, it is a digital sensor issue.

wrong. pf is caused by a lens not focusing light at the far ends of the visible spectrum the same as light from blue to red. that's why pf varies from one lens to another and from one f-stop to another. digital is just usually better than film at "seeing" the pf produced by lenses.

From my experience, fringing does happen on film. I imagine that major awareness of it didn't exist until pixel peeping though.
Here's a corner crop from a 2400 dpi scan of a Kodak Portra 400 VC negative shot with my SMC 6X7 45mm f/4 lens.


Unless this is somehow caused by scanning, I've definitely run across it a few times coming from this lens and different films.

there may be a bit of pf in that photo, but it mostly just looks like blue/yellow ca.

[snake]

I've got an M85 and never really noticed any abnormally large amounts of PF. Very nice lens.

[Stone G.]

wrong. pf is caused by a lens not focusing light at the far ends of the visible spectrum the same as light from blue to red. that's why pf varies from one lens to another and from one f-stop to another. digital is just usually better than film at "seeing" the pf produced by lenses.
there may be a bit of pf in that photo, but it mostly just looks like blue/yellow ca.

True. And one should recall that M-lenses were optimized to reduce aberrations otherwise visible on analogue film - and most films had and have a rather different spectral sensitivity than digital sensors, whether with or without blocking filters. See for example: Wikipedia:

Purple fringing - Wikipedia, the free encyclopedia

[timo]

I don't find any of my M lenses particularly susceptible. The main culprit in my collection is the FA135/2.8 wide open. Even that's only a problem with really high-contrast edges.

(PS: I love the idea of a fridge master, OP. I know several people who could claim that title ... )

[Jonathan Mac]

The M85 doesn't so much purple-fringe as blue-fringe. 80% of it is gone by f/2.8 and I've never found it to be a problem. It's a beautiful lens.

I've never seen any really bad purple fringing in my images and I have a lot of Ms and I like to shoot with wide apertures.

[wombat2go]

SMC Pentax -M 1:2 85 mm
Pentax originally said
"Creates a soft focus effect in the areas just beyond the depth-of-field. Ideal for portraiture, indoors or out. The moderate distance between the photographer and the subject makes this lens particularly excellent for pictures of children, , night time street scenes, illuminated buildings, and for theater and ceremonial pictures."

I have never used this lens.
So here is a "fence test" wide open at f/2 showing the out of focus effect.
https://www.box.com/s/wefkg1ly4wmlu3m39zv2

A messy tree branch shot at f/11
https://www.box.com/s/pr1mvdsukww8xpixig0n

"portrait" (I don't put family members up)
At f/2 , difficult to focus so used the Magnifier M on the face.
https://www.box.com/s/i6nnfe3sdhnslsmpimn6

On the fence test full size on the 22 inch Eizo, , I do see some obvious purple fringe on the out of focus zone near to the camera, but I suppose the lens was not intended to be framed like that and Pentax said "just beyond...".
Maybe that is the origin of Yusef's query?
The fringing on the out of focus beyond the subject looks OK ??

Today I will try some family shots with SMC Pentax -M 1:2 85 mm on the MX with some Fuji 400.
But after the above lesson will stop it down f/5.6 or so to ensure focus.

[Jewelltrail]

It is worth adding that DSLR sensors play a large role in "blooming" issues. Particularly with the CCD sensors found in many DSLRs does blooming become an issue, whereas CMOS sensors handle the issue much better. The subject can get complex, but there is some good discussion here, with endless more to be found in a Goolge search:

OK1000 Pentax Blog: Reducing Purple Fringing and Sensor Blooms

[vonBaloney]

EDIT:My apology, I left Pentax a couple of years ago & all my efforts have been in Nikon ever since. I made a mistake---It was not the M 300 f/4 which was so poor--It was the K 300 f/4. My experience with the M 50 1.7 & 200 f/4 is accurate.

That's right -- I don't believe there is plain M 300/4, it only came in a green star(*) version. It is known as a fantastic lens, and is completely different than earlier K 300/4, which I don't think is that well-regarded, fringing or not.

[Jean Poitiers]

... Steve

FWIW...I only own a few lenses that cause my K10D to fringe at all. Care to guess which ones?

Please do tell ...

[stevebrot]

wrong. pf is caused by a lens not focusing light at the far ends of the visible spectrum the same as light from blue to red...

Wrong...PF is not the same as CA (what you described). CA can cause a purple "fringe", but not all purple is PF. The difference is readily apparent on inspection. CA does not "bloom". PF does. As I noted above, PF is a digital-only phenomenon. Read any lens test from the "film era" and you will see no mention of PF.

See:

Chromatic aberration - Wikipedia, the free encyclopedia

Steve