sensor flare: do the pentax macros have it? Tamron 90/2.8?

[lorriman]

As you may have seen in other threads I've recently procured a Tamron 90/2.5 (not 2.8 ) only to discover that it has a case of sensor flare that happens to affect my purposes. Certain kinds of photos clearly show it at smaller apertures, particularly backlit. You can see a an example in a previous thread here.

As it happens I've also discovered that the Tamron's 1:2 is not enough for taking full sized snaps of negatives, my primary purpose. I need more like 1:1.5. Unfortunately adding the extension tube degrades resolution due to the close-range-correction 'floating' rear elements which I've read elsewhere is because they are highly tuned to the lenses normal range and defeated by extension tubes (supposedly some Zeiss lenses have a CRC adjustment for this reason).

With these issues I'm now looking in the direction of other solutions. The Tamron 90/2.5 does make awfully nice portraits, however, so I'm considering keeping it as my photographic mainstay is film anyway.

I would be grateful if anyone could try the sensor reflection test to see if the pentax MF macros, such as 100/4 and 50/4, are similarly afflicted. I'm also very interested in the Tamron 90/2.8 (72B) if anyone has it. It seems that the Pentax-A 50/2.8 also has CRC 'floating' elements, so I'll be avoiding it as it only goes to 1:2.

I've found the easiest way to do this is a variation of the method in that link. With a darker background, and stopped down to f11, f8, f5.6 and f4 (to cover differences in performance and camera crop up to 2x for 4/3 users) position a light bulb just peaking in to the image at the side or top. Stopping down more makes the flare more acute, but that range is usually the peak performance and happens to coincide with my own practical use (I don't require massive dof). Of course if anyone is inspired to test at all apertures then that would be great to know also. Please do state what camera it is and the crop: it makes a difference as on crop the performance peak and sensor flare moves up an aperture due to a change in effective aperture (f7 rather than f11 on my Tamron tested on 1.6 crop).

I might try to build a chart out of any results, averaged. I've always loved generating graphs. Subjective comments are just fine (ie. I can only just see some flare, I can see some flare, I can see lots of flare).

I've read a rumour that the 100/4 suffers from flare generally which seems a bit of a surprise for an SMC lens? Presumably this is a problem in backlit situations (my favourite). Any experiences?

Thanks for any help,

crazy MF lens person

[edit: changed title to 'tamron 90mm" as was previously referring to a lens that may not even exist]

[visualopsins]

No problems with sensor reflections using any M42 version of Asahi Pentax Macro-Takumars or Bellows-Takumars 4/50 and 4/100, on Canon XT (350D) or 5D1. The exit elements are not flat on any of those lenses, based on the lens diagrams and observation.

I have not noticed excessive flare with 4/100 Macro-Takumar on either camera. Of course, all lenses flare; coatings can reduce, but can not eliminate, flare. A hood can sometimes better control flare than coatings by keeping the strong direct out-of-frame light off the lens front element. Point any lens so Sun is just out of frame and you will see LOTS of flare; sometimes it is very beautiful with many rainbow colors.

[lorriman]

[visualopsins]

I did not test that way, no. Maybe wrong, I think using the much brighter Sun against the relatively dark Sky is a similar test -- all lenses flare under those conditions, but lens coatings do reduce the amount of flare considerably. I have not noticed out of focus highlights, such as that produced by backlit foliage, causing undue flare or sensor reflection bright spots, in any of hundreds of photos, only beautifully rendered bokeh. Takumar bokeh tends to be more 'busy' than the creamy Zeiss bokeh but not as busy as some other lenses; some like it some 'hate' it.

Now I'm remembering the seeing over on http://www.fredmiranda.com/forum/board/55 some 52B/52BB sensor reflection flare examples and some very detailed long and interesting discussions about it; someone even noticed a Bayer pattern in the flare image(!). There are also many threads there discussing technical aspects of Bokeh. (Just be sure to return to this forum! ) Look there for the "What is 3D" thread, for example; there are several '3D' threads here too.

There is also a fellow at University of Kentucky attempting to use bokeh as a means to develop lens abberation correction Photoshop plugins, by measuring the size and shape of wide-open out of focus highlights. Iirc those posts are over at http://www.pentaxforums.com/forums/ .

I'm really satisfied happy with my 4/100! High contrast and high resolution, often with for example sunlit flowers against shade, the flower is rendered in awesome detail on a near-black background! I like to think the Tak has better IQ than the 52B/52BBs; they are at least very close in performance, excepting the sensor reflection issue. Good luck in your search. (I have another one for sale here if you're interested)

[lorriman]

[AhamB]

[haroneyn]

I have the SMC Macro Tak 100mm f/4 and the Super Macro Tak 50mm f/4, and often use them with the sun back-lighting plants, flowers, trees, birds, etc., without any major flare issues. I always use lens shades (love those nice metal shades for the Taks). Both these lenses are superb (regardless of multicoating).