Minolta MD 17mm 1:4

[Wiener]

A question to those who have encountered and discussed such problems elsewhere on the forum, if you don't mind?
Apart from what appears to be the 'usual' learning curve to acheive images in focus, this lens seems to produce reasonable images with good contrast and colour. However, there is evidence of colour seperation close to the edges where horizontal lines are set against bright light. For example, on the attached image the cross above the chapel roof shows blue rims above and red rims below the horizontals. I am guessing this is 'normal' due to a mis-match of lens design and sensor. This may not prove to be such a huge problem as it is not present in many images (and certainly not in b&w!)
And comments from the old/young and wise will be much appreciated.
all the best,
Andy

 

[wok64]

Nice lens, seems to perform quite well, without any color distortions in the edges. Your blue and red fringes is a typical lens defect called chromatic aberration /http://en.wikipedia.org/wiki/Chromatic_aberration). It has nothing to do with the sensor not matching the lens.

Best regards,
wok

 

[Wiener]

Hi wok,
thank you very much for the advice and web-link. All is much clearer to me now! After reading the wikipedia page you mentioned I retried the JPEG rather than the DNG image at high magnification. I found that the colour fringing almost non-existent in the camera processed image so am much more content now! As I bought the lens 30 years ago it had more sentimental value to me than than practical use...but I think it has now found a very good new life as an 'occasional' on the front of my M-mount. Of course it is a little 'chunky' but no more so than the A16 zoom...
All the very best,
Andy

 

[Wiener]

Who would have thought that it would be so hard to focus a 17mm lens? :?
But getting there!
Andy

 

[Wiener]

A 'Henry Moore' swimming beautifully outside Karlskirche, Vienna.
Finally begining to like this lens combination! Though ploughing a lonely furrow I would imagine...
Andy

 

[olyz]

Andy, this is a very nice photo! I like the contrast between the curves and the columns, the black and the white!
Christian

 

[Rog Tallbloke]

Agree, plus the reflections from the water lend a Taj Mahal like serenity to the scene.

 

[thelps]

At 17mm some CA is to be expected IMO. how much depends on many lens design factors.
As these lenses are designed with film in mind we sometimes find that they show issues when using them on digital.

I've seen worse CA than you sample here. I believe some can be corrected in software but I've never really done this myself.

 

[Wiener]

Just an update on the focusing problems I mentioned with my 17mm f4 Rokkor lens.
As I have been having a similar problem with a my 24mm Rokkor MD f2.8, I set up a rough trial today to try and better understand what is going on.
The procedure was simple; I set the GXR and M mount on a tripod with the test lenses set to f8.0, the EV at +0.3, with the shutter setting itself in A mode.
With the lenses set to infinity one would normally expect pretty much everything to be sharp with a 17mm set to f8; however not so! I pulled the focus back about 1mm of revolution and tried again. This was repeated until 6 shots had been taken. On the computer it was clear that around 3 or 4 mm of revolution away from infinity was required to bring objects 150-250m away into sharp focus, even at f8. This can only mean that with this M mount + MD adaptor + 17mm lens combination, the lens is focusing beyond normal 35mm film-plane infinity.
A similar situation was found with the 24mm. However, with the 50mm f1.4 and 85mm f2, everything was wonderfully sharp, so this seems to be a problem affecting only the wide-angled Minoltas, and not a design problem or defect within the adaptor.
Incidentally, my 15mm LTM Voigtländer focuses correctly at infinity when I followed the same procedure as described above.
I will need to give this more thought before deciding to sell the offending lenses; after all I could just mark the lens barrels with a new infinity mark, but it much easier if infinity means infinity when one wishes to shoot in a hurry.
It would be great to try them out on an M9 just to see how they performed on a FF platform. however, that won't be happening this week, or probably the next one either!
Andy

 

[Blow-in]

Andy,

That's an interesting explanation about the focusing issue and I suppose it is not that surprising that a precise optical lens can be affected when it is mounted on something that it was not designed for....I guess it's the extra thickness of the adapter that it is the issue and it reminds me a bit of trying to use the GT-1 on the GRD4 with a step-up ring...horribly soft at everything apart from the centre but brilliant on the GRD without the adapter. Lens's can be calibrated...I wonder if the focusing ring can be adjusted to suit your mount? Your Henry Moore shot is reason enough to persevere.

On the CA issue, in a way I'm not surprised that it is less noticeable in the JPGs. Having ploughed my way through this A12 50 review, I'd need strong persuasion to use RAW over JPG for most situations. http://www.dpreview.com/reviews/RicohGXRa12

Richard

 

[Wiener]

Richard,
it must be said that before I reminded myself of the Henry Moore shot, I was on the point of giving up on the 17mm. But when it is good it is really good! And the effective focal length of 25.5mm equivalent is actually very handy for around the town shooting...
I will try and reach a deeper understanding with my 24mm which is proving even less lovable...but it is an ideal focal length for me though (36mm equivalent) so will persevere a little longer before filing for divorce!
As for the JPEG v's RAW you and DPReview are not alone in thinking GXR JPEGs are easier. Most of my recent posings are all from JPEGs....I wonder how are others fairing?
Andy