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 Replies: 10 / Views: 2,204 |
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Pillar of the Community
2087 Posts |
Following a discussion on this thread: https://goccf.com/t/159091I decided to test out a very old Minolta lens (minolta AF 35-70mm) so as to see the difference an extension ring would make. A long time ago I had tried extension rings out on a Sony kit lens and had been extremely disappointed(As a result I thought the extension rings were a waste of money). I didn't throw the extension rings away so today I used the 20mm ring to see what the rings could actually do. So first off my A 65 was set to manual for both photographs I used ISO 100, and an F value of 5.6. From memory 5.6 is supposed to be the sharpest for that lens. For both photographs I had to use the cameras electronic zoom( 2 Times in both cases) for the first photograph the converted enlarger stand ( my copy stand) indicated the focus was occurring at 57.8 cm ( this is indicative only as the lens to subject distance will be slightly different). Before I post the first photo note I was taken in day light with a 5600K LED light.....usually the best shots from my rig are taken after dark. First photo with out the 20mm ring  With nothing changed except the addition of a 20mm extension ring..immediately the indicative focus distance was down to 41 cm. This is the result  The only editing I did for both pictures was to remove the background. I think the most impressive thing is the change in image size using the 20mm extension ring..I have certainly changed my views about the rings.....and I am slightly annoyed I had given that cheap old 35 -70mm lens to my daughter......Next month when my budget allows it I will get another one! Edited by austrokiwi
09/29/2013 09:23 am
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Moderator
 United States
23522 Posts |
Keep in mind, the "electronic zoom" in that camera is just a digital zoom; the camera's internal software is arbitrarily upsizing the image by the factor you chose. "Digital zoom" is a misnomer, an inherently destructive process as it's just grabbing the center of the image and doubling its' size, and sharpness suffers greatly as a result. You could do the same thing in postprocessing; just double the size of the image you have open in the software. Further, on the A65 that digital zoom only works in 12MP mode, so in order to utilize it you're only using half of the camera's megapixel capability....if you set the image size to use all 24MP, you'll get the same ultimate image size with none of the inherent disadvantages of the digital zoom.
Therefore, the second magnified image speaks volumes about the original optical quality. If it's that sharp after having its' size doubled in software, the original had to be tack-sharp and the 24MP version will be equally sharp. And you can still use the lens' optical zoom with the extension ring....
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Pillar of the Community
 2087 Posts |
The electronic zoom is probably the reason for the not so sharp center of the coin.....Its a little darker now so I borrowed that lens from my daughter and tried again, but without using the cameras electronic zoom. To get the coin to fill the field I had to go to the 33mm Extension ring....and had to raise the coin up from the copystand base. I actually measured the lens to subject distance;10cm. I didn't spend too much time settign up the shot( rough and ready just to see what the old lens and a extension ring could do. The biggest immediate problem was DOF at 5.6 the designers initials "KG" weren't so sharp... so I ignored the "book" and went to F8:  That little 35-70mm Minolta lens can really do it. I am really impressed....I can say from experience that the Sony 18-55mm kit lens can't do that! My daughter who uses my old A380 has independently decided she prefers that little Minolta lens also...her view is non technical....she says it just takes better pictures then she rubs it in adding she likes the antique colors ( meaning 1980s!) I suspect she is just trying to wind me up with that one!! End of October I'm off hunting for a new, for me Minolta 35-70mm with macro function. |
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Moderator
United States
23522 Posts |
That looks like one heck of a decent lens, considering their real affordability. If the white box is the full frame of your 24MP sensor, then the coin itself is going to be huge when cropped out - as large as anything we're doing with more bespoke rigs since you have 4000 vertical pixels at 24MP - and then downsized for posting purposes it'll likely be as sharp as anything you see posted here.
Like.
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Pillar of the Community
2087 Posts |
There are several varieties of the Minolta 35-70mm. The one I have "rediscovered" is one of the earliest. All metal construction even the lens hood is metal! So people can see which particular lens I mean here is a photo with the lens actually set to macro mode. to its left is the Sony kit lens. Funny thing is both lens are kit lenses its just the build quality is very different. The minolta is physically smaller than the sony lens but it feels heavier and much more solid. The Sony lens feels like cheap plastic!  |
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Pillar of the Community
United States
4038 Posts |
Really nice result! I suspect the lens has a better macro capability than the typical "zoom macro" lens.
I assume you're working in the macro range on the focal length adjust ring, correct? There are several types of zoom macros. This type extends out to max focal length, and then goes into the special macro range beyond that. The assumption the manufacturer makes is that you'll adjust the focus to as close as it can go, then push the macro button in order to get even closer. The lens then significantly changes its internal structure, shortening its focal length and adjusting lens formula for close-focus field flatness. The focus ring should be on minimum focus distance during macro shooting.
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Pillar of the Community
2087 Posts |
Quote:
I assume you're working in the macro range on the focal length adjust ring, correct? Correct Quote:
This type extends out to max focal length, and then goes into the special macro range beyond that. Yep I recall when I first got the lens I was confused how the macro worked. The button is really just a lever....you turn the focus ring to the maximum level then "lift the button and turn the focus ring beyond the maximum. Putting the lens into macro mode switches off Auto focus. I know some people modify the lens by lifting the rubber and insulating the copper band that acts as the switch to turn off the AF. Quote:
If the white box is the full frame of your 24MP sensor SsuperDdave: yep the white area is the full frame. Ireally wish I hadn't given that lens to my daughter! Knowing my luck( or rather my daughters) Murphys law will come into play and I will find the lens of her's was a Manufacturing fluke LOL Edited by austrokiwi
09/29/2013 4:55 pm
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Pillar of the Community
2087 Posts |
I did some internet research: I think that instead of hunting for another Af version. I will hunt out a, sometimes, more expensive manual F 3.5 version. Apparently Leica was impressed enough to re-badge that lens in cooperation with Minolta. Leica may have also been involved in the design/and or build. Leica badged the Minolta lens as "Leitz Vario-Elmar R 35-70 f3.5"( So it should have been no surprise, had I known the history, that little AF descendant performed so well). The only thing is the older lens is completely manual and the A 65 won't register it( no confirm chip) here is one review of the original manual version: http://m43pics.wordpress.com/2011/0...-f3-5-macro/Given the "pedigree" of the Minolta AF 35-70 it is no wonder that it outperforms the Sony 18-55mm. They are two lens from two completely different eras. Edited by austrokiwi
09/30/2013 06:14 am
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New Member
United States
41 Posts |
I believe that Sony A65 does not have digital zoom as most think of it, but Smart Telephoto. As I understand it, Smart Telephoto takes the 6mp in the center of the sensor, so their is no degradation of image the way digital zoom does. You just end up with the center of a 24mp shot. Similar results can be achieved by cropping the 24mp image, not the post processing done by other cameras for digital zoom.
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Pillar of the Community
2087 Posts |
Eastriding: thanks for the info the only thing I would note is the difference between the second photo ( 2 times magnification) and the 3rd no magnification. I expect you are right but that might not make any difference to the lack of sharpness. Then again...it may mean my focusing was better in the last shot. ( I have to make sure I use my reading glasses to get the focus right) Also the last photo was possibly better because I got the lens to subject distance down to 10cm.
Edited by austrokiwi
10/01/2013 12:55 pm
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New Member
United States
41 Posts |
I like the look of the lighting and the sharpness in the last photo a lot!
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Replies: 10 / Views: 2,204 |
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Posted 09/29/2013 1:25 pm
