Sony Diaries #997: micro adjusting a Minolta 35-105F3.5-4.5: A Methodology

I recently purchased a Minolta 35-105F3.5-4.5 lens through Kijiji, in very good condition, clean elements, no grease on the aperture blades, very few markings, for $40CDN. It's a typical Minolta with an all metal body, built like a tank. I don't know when this older version was released but I do know the new version was released in 1988. This would make this lens at least 30 years old. Zooming is still silky smooth, with just a touch of stiffness to prevent zoom creep. I will have to go out and take some pics, fully expecting pics with the legendary Minolta colours and here too: an unquantifiable creamy bias toward the warm side, soft-ish micro contrast without sacrificing overall sharpness.

As a relatively slow zoom lens (F3.5 at wide and F4.5 at tele), micro adjustment is not a critical issue but I still wanted to be in the immediate vicinity of accurate focus. The default  on the camera (for any lens) is at +/-0. Below is my test subject, chosen for it's intricate details.

Not knowing where to start, I used the whole range on my camera: -20 to +20. 1/100 F4.5 ISO2000.

Without a doubt, micro adjust -5 is the sharpest in the set. I shot 3 more frames in the neighbourhood of -5.

The sharpest is towards -3 so I'll set the camera at -4. At f4.5, the DOF is not shallow at all but -4 puts me as close to the middle as possible. Below are the final shots with micro adjust -4, taken at both 35mmF3.5 and 105F4.5, all at their respective minimum focusing distance (MFD).

Micro adjust is not of much use with slower lenses, particularly when they are used for more than the MFD... DOF is not a concern. In the case of the Minolta 35-105F3.5-4.5, I determined the micro adjust to be -4... not that far from the default setting 0.0.

I'm open to suggestions as to how I may improve on my methodology. All in all, not bad for a $40 lens.

Sony Diaries #994: (The magic of) Micro Adjust

There's nothing more frustrating than a heretofore sharp lens that's not quite all there on a different body. It's also frustrating that a lens that should be sharp is unsharp to varying degrees on different bodies. Since the bulk of my lenses are legacy lenses (Minolta AF) that are 20-30 years old, I started to doubt my skills as an informed buyer on Kijiji and Craigslist. At one point, I just thought my eyes were starting to deceive me.

On my first wedding of the season, the shots on my Tamron 28-75F2.8 were not as sharp on my second a99 body as it was on my first a99 body. Was it time to junk this lens? 

A few weeks ago, I was so lucky to find a Minolta 50F1.4 AF on Kijiji. A cursory check on my a99 showed a sharp lens at f2.8, some CA, and  generally low contrast. CA and contrast can be remedied in post (or even in-camera) but sharpness can't be (clarity sliders and unsharp masks are akin to putting on cologne without taking a shower first).

The price was irresistible ($100 versus $550 for a Sony 50F1.4, $1150 for a Sigma 50F1.4ART). Plus it's rare for a Minolta 50F1.4 to come on the local market. At the very least, the F1.4 means faster focusing in low light, even if the taking aperture would be at 2.8.

I come home and the lens turns out to be even more unsharp on my a77II than it is on the a99.  I love shooting wide-open for shallow depth-of-field but shallow DOF will reveal focusing errors. A lens may focus precisely but not necessarily accurately. A lens may focus a mm or more forward, or backward. A shallow DOF will reveal this right away. I want precision and accuracy. Even on a cheap lens. Then I remembered the idea of micro adjusting lenses. 

Micro adjustment allows us to make a correction for every lens when paired with any camera body so that a compensation is automatically applied; compensation will vary depending on the camera body used.

To jump to my conclusion, my $100 Minolta 50F1.4 is razor-sharp at F1.4, on the spot/plane that I focus on. On the following photos, I focused on "9902". Taken with the same lens on 2 bodies, APS-C and Full Frame.

1/100@F1.4, Sony A77II.  Compensation: -20 (yikes!)

1/100@F1.4, Sony A99.  Compensation: -8 (huge difference with the A77II's -20).

My methodology, adapted from several sources available online,  will be up on a future blog post. Micro adjustment is only available on some, not all, of the newer cameras. the Sony a99 was introduced about 5 years ago. I have since micro adjusted all my lenses which has led to a major difference in sharpness. Micro adjustment is particularly important with fast lenses and macro lenses (slow lenses but typically shot wide-open and very close to the subject resulting in very shallow DOF).

The Sony Diaries #4: High ISO? no worries with the Sony a99

There has never been a free lunch with high ISO's. Using high ISOs (ISO1600 and higher) meant putting up with noise/grain, colour shifts, and overall image degradation. Back in the film days, rating an ISO400 film at ISO800 was, literally, pushing it. In digital, as sensor technology (and size) evolved, the high ISO quality boundaries expanded; still, an image taken at ISO3200 shows image degradation in comparison to one taken at ISO400 (a difference of 3 stops).

I knew that, in theory,  a well exposed image may be taken at high ISO's without noticeable or significant image deterioration. I never had much success with this theory so I kept my ISO rating at ISO800, maybe ISO1600 for dark reception venues, even with my full frame Canon 5d2.

Enter the Sony a99. This is a full frame camera with what I think is (shared by reviewers across the internet universe)  the best, unsurpassed, AWB and light metering implementation ever. Coupled with Sony's SLT technology, with its phase detect LIVE VIEW (on the industry's highest resolution EVF OLED finder and matching screen) which means what-you-see-is-what-the-sensor-gets-exactly (along with the thumb wheel for instant +/- EV adjustment), my images are almost always well-exposed!

I have now taken to using the AUTO ISO setting (ISO50-ISO6400) when I am on either Aperture Priority or Shutter Priority Mode. My images are almost always well-exposed and colour-balanced.

Here are samples of what I mean (as well as showcasing the Sony a99's micro-adjust feature):

Zeiss 24-70f2.8 at 50mm, 1/60@f3.2, ISO2500, full-frame 24MP

detail area from above, cropped to 1.5MP

Zeiss 24-70f2.8 at 50mm, 1/60@f3.2, ISO2500, full-frame 24MP

detail area from above, cropped to 2.1MP

Tamron 70-200f2.8 at 200mm, 1/125@f3.5, ISO6400, full-frame 24MP

detail area from above, cropped to 1.0MP

The image taken with the Tamron is note-worthy in that this lens was a so-so lens when used with the Sony a65 and Sony a57, consumer-oriented cameras without a micro-adjust feature. I was prepared to live with this since this Tamron is priced at less than half of what the Sony G version and the equivalent Canon and Nikon offerings go for. What I didn't realize is that the lens is actually innately very sharp; the a99 allowed me to micro adjust the focus plane so that the Tamron potential is realized!

Needless to say, I'm a Sony fan!