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Minolta ROKKOR-TC 135mm f/4 Bellows & Extension Bellows
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PostPosted: Tue Mar 22, 2022 2:58 pm    Post subject: Minolta ROKKOR-TC 135mm f/4 Bellows & Extension Bellows Reply with quote

A stroll around my garden with a contemporary setup today:

- Minolta ROKKOR-TC 135mm f/4 bellows lens
- Minolta Extension Bellows (the first one they made, still branded CHIYODA KOGAKU on the back)
- On a SONY A7s camera

This lens is the bellows version of the Minolta ROKKOR-TC 135mm f/4; pretty much minus the focusing helicoid and possibly optimised for macro use. It has an M39 Leica thread and comes with a Minolta L-Adapter, to enable it to be mounted on the Minolta SR mount. It has 12 rounded aperture blades, resulting in pleasing bokeh balls.

The bellows is Minolta's first bellows; a fairly compact folding design, compact enough to use as a travel bellows but nevertheless with decent extension and surprisingly sturdy.


The set: ROKKOR-TC 135mm f/4 bellows lens with hood, M39 to SR Minolta L-Adapter & key, Minolta Extension Bellows:


On the fully folded bellows this lens focuses well beyond infinity, so this is the minimum practical extension shown below:


Although a compact folding bellows, it allows for a very decent extension:


Classic style aperture:


#1:


#2: 100% centre crop of #1


#3:


#4:


#5: 100% centre crop of #4


#6:


#7: 100% centre crop of#6



Some images at a 5m distance from my garage door show good correction for distortion, but it is losing its sharp edge. This lens probably has been optimised for macro range performance compared to the regular ROKKOR-TC 135mm f/4.

#8:


#9: 100% centre crop of #8


#10: 100% corner crop of #8


Minolta, much later, released another compact travel bellows. It is even more compact and much lighter, but also more limited in its use, with shorter extension, no focus rack, no tripod bush and (arguably no longer necessary) no rotatable camera mount.

This later Compact Bellows tends to go for fairly high prices at times, whereas the older Extension Bellows can often be picked up for very little money.







PostPosted: Tue Mar 22, 2022 3:14 pm    Post subject: Re: Minolta ROKKOR-TC 135mm f/4 Bellows & Extension Bell Reply with quote

RokkorDoctor wrote:
A stroll around my garden with a contemporary setup today:

Minolta ROKKOR-TC 135mm f/4 bellows lens - This lens is the bellows version of the Minolta ROKKOR-TC 135mm f/4; pretty much minus the focusing helicoid and possibly optimised for macro use.
...
Some images at a 5m distance from my garage door show good correction for distortion, but it is losing its sharp edge. This lens probably has been optimised for macro range performance compared to the regular ROKKOR-TC 135mm f/4.


Some time ago I've been comparing the bellows and the helicoid version of the ROKKOR-TC 135mm f/4 at infinity - they both had exactly the same weaknesses. So I suspect them to have the same optical computation. Triplets usually have quite a bit of field curvature, if the other aberrations are sufficiently corrected.


RokkorDoctor wrote:

#2: 100% centre crop of #1


When taking images of red flowers, the red channel easily gets over-saturated (=over-exposed); this results in large, undifferentiated red blobs without much detail. Those problems are exacerbated by the fact that your 7s has just 3 MP (!) red pixels. The other 9 MP simply are extrapolated from the green and blue pixels - and those pixels probably don't get much light when everything is red. Taking good images of red flower is not that easy.

S


PostPosted: Tue Mar 22, 2022 3:41 pm    Post subject: Re: Minolta ROKKOR-TC 135mm f/4 Bellows & Extension Bell Reply with quote

stevemark wrote:
RokkorDoctor wrote:
A stroll around my garden with a contemporary setup today:

Minolta ROKKOR-TC 135mm f/4 bellows lens - This lens is the bellows version of the Minolta ROKKOR-TC 135mm f/4; pretty much minus the focusing helicoid and possibly optimised for macro use.
...
Some images at a 5m distance from my garage door show good correction for distortion, but it is losing its sharp edge. This lens probably has been optimised for macro range performance compared to the regular ROKKOR-TC 135mm f/4.


Some time ago I've been comparing the bellows and the helicoid version of the ROKKOR-TC 135mm f/4 at infinity - they both had exactly the same weaknesses. So I suspect them to have the same optical computation. Triplets usually have quite a bit of field curvature, if the other aberrations are sufficiently corrected.


Maybe they did just chop off the focus helicoid. Wink

stevemark wrote:
When taking images of red flowers, the red channel easily gets over-saturated (=over-exposed); this results in large, undifferentiated red blobs without much detail. Those problems are exacerbated by the fact that your 7s has just 3 MP (!) red pixels. The other 9 MP simply are extrapolated from the green and blue pixels - and those pixels probably don't get much light when everything is red. Taking good images of red flower is not that easy.

S


I did not realise that, thanks for the hint. As a matter of cause I tend to have my camera set at 1 stop underexposure anyway, as I don't like the way it can clip the highlights when set at zero.

Checking that image, my in-camera histogram indicates the red channel is nevertheless just saturating a tiny bit (really hardly at all), but curiously the same image loaded in Photoshop does not show any clipping whatsoever in the red channel. Maybe something to do with the JPEG processing in the A7s; perhaps the in-camera histogram shows the raw sensor just beyond the edge of clipping, which gets magically ironed out (or is it messed up Wink ) when combined with the extrapolation from the green and blue pixels in the JPEG processing. I'll dial in another half stop underexposure next time with the bright red flowers Wink

For what it is worth, my eyes must have A7s retinas, as that is the way those flowers looked to me in the flesh...!


PostPosted: Tue Mar 22, 2022 6:56 pm    Post subject: Re: Minolta ROKKOR-TC 135mm f/4 Bellows & Extension Bell Reply with quote

RokkorDoctor wrote:

Checking that image, my in-camera histogram indicates the red channel is nevertheless just saturating a tiny bit (really hardly at all), but curiously the same image loaded in Photoshop does not show any clipping whatsoever in the red channel.


When I look at the red channel of the crop shown above, the entire (!) lower left quadrant has a "red" value of "255", which means it's over-saurated:



RokkorDoctor wrote:

For what it is worth, my eyes must have A7s retinas, as that is the way those flowers looked to me in the flesh...!

Well, sure enough, when looking a your images using my smartphone, things look pretty natural as well. On my calibrated screen (which matches very well with the proofing and the results of high quality offset printing) however, the red looks really oversaturated (as it should, since the red channel clearly is at "255" in >25% of the image crop shown above !!).

Interesting and a bit strange! But I understand now why you on your screen probably have a rather good looking image. Nevertheless, and especially for printing purposes, it would be better not to have large areas with over-saturated channels (e. g. red "255").

S


PostPosted: Tue Mar 22, 2022 10:43 pm    Post subject: Re: Minolta ROKKOR-TC 135mm f/4 Bellows & Extension Bell Reply with quote

stevemark wrote:
RokkorDoctor wrote:

Checking that image, my in-camera histogram indicates the red channel is nevertheless just saturating a tiny bit (really hardly at all), but curiously the same image loaded in Photoshop does not show any clipping whatsoever in the red channel.


When I look at the red channel of the crop shown above, the entire (!) lower left quadrant has a "red" value of "255", which means it's over-saurated:



RokkorDoctor wrote:

For what it is worth, my eyes must have A7s retinas, as that is the way those flowers looked to me in the flesh...!

Well, sure enough, when looking a your images using my smartphone, things look pretty natural as well. On my calibrated screen (which matches very well with the proofing and the results of high quality offset printing) however, the red looks really oversaturated (as it should, since the red channel clearly is at "255" in >25% of the image crop shown above !!).

Interesting and a bit strange! But I understand now why you on your screen probably have a rather good looking image. Nevertheless, and especially for printing purposes, it would be better not to have large areas with over-saturated channels (e. g. red "255").

S


Hmm, strange.

I did just double check, and noticed that when I said in Photoshop the red channel did not look oversaturated, that was referring to the AdobeRGB JPEG that came out of the camera, not the sRGB JPEG that I posted, my bad... Rolling Eyes

This may be my lack of Photoshop skills, but it appears it resulted from me first lifting exposure up a bit in PS, but still such that none of the RGB channels were saturated (the red channel almost), and then later converting from AdobeRGB to sRGB. That last step then (unbeknownst to me) over-saturates the red channel. There is probably something about the profile conversion in PS CS6 that I don't understand. I thought AdobeRGB has a predominantly wider gamut in the green/cyan region, not the red, so wasn't expecting the profile conversion of a near saturated red channel in AdobeRGB to result in a clearly saturated red channel in sRGB once converted.

EDIT: maybe something to do with preservation of the white point and/or colour temperature?

Anyway, doing the AdobeRGB to sRGB profile conversion first, and then correcting for exposure, seems to give a much different result, which are the two images below. These, in my PS do not show any saturation in the red channel (I tried to get as close to the original crop as possible).

If you agree these are better, then I need to find out more about the ins & out of profile conversions in PS CS6, because it doesn't seem to behave the way I was expecting, given the gamut differences between AdobeRGB and sRGB...

I do have a calibrated screen, but it covers sRGB; it is not an AdobeRGB gamut screen.





PostPosted: Tue Mar 22, 2022 11:01 pm    Post subject: Reply with quote

Mystery solved - thanks for your time!

Yes, these images now look good!

Much appreciated!!

S


PostPosted: Wed Mar 23, 2022 1:16 am    Post subject: Reply with quote

Same set-up but with Sony NEX-7 ad Zhonghi MD-NEX Lens Turbo

Surprisingly sharp results considering the age of these things
#1


View of a subject


#1


Final results


#1


#1


PostPosted: Wed Mar 23, 2022 8:53 am    Post subject: Reply with quote

michelb wrote:
Same set-up but with Sony NEX-7 ad Zhonghi MD-NEX Lens Turbo

Surprisingly sharp results considering the age of these things



Like 1

Interesting to see someone with the exact same lens setup Smile

The old ROKKOR presets are often overlooked. Allowing for the inevitable CA on the longer ones, I like the way they image. Esp. the ROKKOR-TC 100mm f/4, but also the TELE ROKKOR-QE 200mm f/5. And all the Rokkor tele presets have nice round apertures.

Other than that, I find preset lenses to work a treat on a mirrorless camera with live view and focus magnifier. No need to count aperture ring clicks.


PostPosted: Wed Mar 23, 2022 9:13 am    Post subject: Reply with quote

stevemark wrote:
Mystery solved - thanks for your time!

Yes, these images now look good!

Much appreciated!!

S


No, thank you for pointing it out!

My hearing is very good for my age, but unfortunately the same cannot be said for my eyesight. This means I have to take more notice of the levels histograms. Especially after a profile conversion! lesson learnt.

I did experiment with a few different rendering intents for the profile conversion. Normally I have it set to the generally recommended Relative Colorimetric, which I just was reminded that it can end up clipping channels when colours go out of gamut. I was expecting Perceptual to do better here, but it still clips the red channel a fair bit!

Perceptual rendering intent in Photoshop does not appear to do quite what the below source suggests...

https://www.cambridgeincolour.com/tutorials/color-space-conversion.htm

Looks like I will need to get into the habit of re-checking the levels histogram after the profile conversion, and manually reduce exposure as required before converting from AdobeRGB to sRGB. As I said, thanks for pointing it out; lesson learnt! Wink


PostPosted: Sat Mar 26, 2022 12:55 am    Post subject: Reply with quote

Hey, that is just like the set I started my tele, portrait and macro pictures with on a SR-1!
It was a cheap solution, I couldn't pay more money for my gear.
A pistolgrip with cable release made the set complete for me in 1966. Laugh 1


PostPosted: Mon Mar 28, 2022 9:24 am    Post subject: Reply with quote

Everyday is a school day at MFLenses!
Laugh 1


PostPosted: Mon Mar 28, 2022 3:52 pm    Post subject: Reply with quote

I must seek out the 135 bellows lens. I have the 100mm, an f4 iirc.as for minolta bellows I have the auto bellows III. It is a much heavier but more versatile thing as it allows some shift and tilt controls. In conjunction with the MD to m42 adapter that came in in some lot of gear truly a tool adaptable to myriad of my enlarger lenses. I also have 2 copies of the compact bellows. One of which I swapped out the MD mount for a NEX mount.