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Various points about using normal lenses with extension tubes for macro
#1
Gents,
 
as I told you some time ago, I'm concentrating on flower photography (still for a couple of weeks; then I hope to resume some journey and do landscapes again). In particular, I'm using four non-macro lenses with macro adds-on: close-up lenses with the SEL70200G and focusing helicoid built into the adapter with a Nikkor 50mm Æ’/1.8D AF, a Helios 44-2, and a Trioplan adapted to E-mount.
 
In general, I'm enjoying the thing a lot, and there are a number of things that I'm practicing, that are beyond the point of optical quality: picking the best flowers, studying the light, tyring to pre-visualise the shot, critically focusing, etc... I think I'm learning lots of things. In particular, I'm also comparing the different bokeh that I can achieve even with lenses of similar focal (such as the Nikkor and the Helios above mentioned).
 
Now I've started looking at the optical quality too. I'm practicing especially in wide-open shots, where the overall look of the photo doesn't require a high resolution (even though I must say that there is a good amount of sharpness on the centre of all the lenses, the Nikkor 50mm in particular). One of the potential problems, instead, are aberrations that are induced by the focusing helicoid, since the lens is forced to work outside of the settings for which its design has been optimised. This happens, clearly, especially with white flowers and dark backgrounds, and worsened when shooting with backlight.
 
In this context, I have some things to ask you. First, whether I'm correctly interpreting as optical defects some details in the samples below (the #1 and #2 are extreme crops).
 
In the first photo (Nikkor) I see green fringing on the rightmost petal (it seems confirmed to be fringing by the fact that an almost identical photo, with the focal plane just shifted a bit, doesn't show any trace of it). On the leftmost petal and the one at the bottom I see purple colour, but not at the border. This flower (Anemonoides trifolia) is supposed to be fully white, but I think this doesn't exclude that some can have traces of purple (I'll ask a flower expert anyway). In your opinion, is this a lens defect?
 
The second sample (Helios), on the other hand, shows purple and green fringing in all the borders of the flower. I think these are clearly optical defects. In this specific case they are probably amplified by the fact that I had to boost saturation a lot here (+40), way more than I usually do, because - I think - of the backlight that produced de-saturated colours out of the camera. In fact, I had to de-saturate yellow as the stamens, after boosing the global saturation, appeared full yellow, while they should be white as in the former photo (same flower species).
 
First question: would a specific macro lens, native E-mount, such as the SEL50M28 totally or substantially better than this? I presume so, but I can't tell.
 
Second question: I've tried to fix the problem in Lightroom by operating with the Lens Correction / Manual / Defringe / Amount (purple and green) sliders. But they seem almost uneffective. I basically don't know the exact way in which the two additional sliders "Purple hue" and "Green hue" work; would they be useful for improving the thing?
 
At the moment I'm dealing with the problem by applying local brushes with desaturation (clearly in the samples I posted I disabled my corrections).
 
All in all, it's not a great problem. I'm attaching one of the full-sizes photos for an evaluation of the final result, and the aberration effect is not jumping to the eyes. The next major buy will be the A6300, so there's no high priority for a native macro lens (*), but... if it makes sense, it could be budgeted for the end of the year.
 
(*) The 50mm Sony macro lens is a 2.8 max. aperture, while the Nikkor and Helios 44-2 are one stop brighter... While it's hard to make a macro good photo at full aperture, in some chances I like what I see. Not sure I could reproduce the same bokeh with the SEL50M28.
 
Thanks.
stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#2
They look like longitudinal aberrations to me or bokeh fringing, green behind the plane of focus and red in front IMHO...

 

  ...these are normal aberrations associated with non APO lenses.

 

  They are not so easy to get rid of in my experience.....the colour correction sliders in lightroom sometimes can be effective but can also cause havoc in other areas of the image if pushed too much... 

 

 A good APO macro lens will be corrected against these fringes.

#3
After some more inspection of other photos, I agree that the purple areas are optical problems too. 

stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#4
Indeed, I see LoCA too. Nice spring anemones. Ours have more yellow stamen. From last week:

[ATTACHMENT NOT FOUND]

Taken with Micro-Nikkor 55mm f3.5 (the old aperture correcting version) on my 6D, wide open.

#5
Colour fringing tools of Lightroom were largely ineffective for removing the purple patches; but totally desaturating the purple and magenta channels, and also applying hue: -100 to both did the trick. Clearly it worked because there are no other objects with purple/magenta components.

 

The SEL50M28 sells for a reasonable price (500€, more or less), but as long as things are fixable in some way, without wasting too long, I'll resist the temptation of buying it...  Wink 

 

@brightcolours Yes, those with yellow stamen should be "Anemonoides nemorosa", the ones with white-ish ones are "Anemonoides trifolia". I've seen the yellow ones too in my session, but they were just starting to open.

 

Nice photo, by the way. I'm still concentrating too much on single flowers, while I like the effect of multiple ones, with the rest of the crowd blurred in the background. So far I wasn't able to pre-visualise them on the field, and only very few attempts were successful... I have to practice a lot.

stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
  


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