Minolta produced an extensive array of lenses for the manual focus SLR system, and thankfully, given the lens mount remained the same throughout the history of the company the lenses from any era will mount onto all manual focus bodies, with varying degrees of functionality. The lens mount, contrary to common belief, is actually called the “SR” mount, not the “MC” or “MD” mount. The terms MC and MD relate to different series’ of Minolta lenses, with different features. All of the lenses, however, use the SR mount.

Another term commonly seen in relation to Minolta lenses is the term “Rokkor”. Like many other manufacturers, Minolta employed a separate name for its lenses, in this case the name “Rokkor” was chosen by Minolta founder, Kazuo Tashima, as a reference to Mount Rokko in Japan, which is adjacent to the Minolta Factory.

The lenses themselves can be broken up into various families, which are detailed below:

  
 
 
 
 
   
Minolta Auto Rokkor-SG 1:35 F=28mm . Note the lack of a meter coupling tab.
    
 
There are at least three kinds of pre-MC lenses: those with no particular aperture functionality (plain Rokkor), those with manual pre-set aperture (also plain Rokkor, mostly Tele Rokkors), and those with automatic pre-set aperture (Auto Rokkor).
 
   
These lenses are very early designs and do not incorporate meter coupling. Accordingly they are normally only of interest to collectors, with the exception of some specific lenses such as the 18mm UW-Rokkor f/9.5, the 100mm Auto Tele Rokkor f/2 or super-telephoto lenses and catadioptric lenses such as the old, big, rare, and unusually fast (given the focal length) RF Rokkor 1,000 mm f/6.3. Naturally, with a mirror lens such as the 1,000mm f/6.3 the absence of meter coupling and automatic diaphragm is of no concern, as the lens does not contain a diaphragm to be stopped down.
  
 
Auto Tele Rokkor-PF 135mm f/2.8
      
         
 
 
 
 
 
The legendary MC Rokkor-PG f/1.2
  
 
These are the first meter coupled (hence “MC”) lenses manufactured by Minolta and are identifiable by their milled metal focusing ring, and plain metal (ie. unpainted) aperture ring. Introduced progressively from 1966 as they were developed, by 1970 they had completely replaced the earlier Pre-MC lenses.

The quality of the coatings on these lenses is as a general rule not as good as those on later MC and MD lenses, and in some cases radioactive compounds of thorium and lanthanum were added to the glass mixture to increase the refractive index. This is apparent in some of the faster lenses such as the 58mm f/1.2 and 85mm f/1.7, where some early versions that included this glass have had their radioactive ingredients progressively decay, discolouring the glass, and giving the images taken with the affected lenses a very warm cast.

 
     
   
The coating materials on these early MC lenses comprised magnesium fluoride, plus “other ingredients”, and the actual coatings were double coated in a process Minolta called “Achromatic Coating”, giving superior colour rendition and light transmission when compared to competing manufacturers. While not as effective as the newer coatings progressively introduced on later lenses, they nonetheless perform very well, and should not be dismissed from consideration when selecting lenses for use.
 
 
The plain metal aperture ring on a 58mm f/1.2
      
 
In many cases the 1st Generation MC lenses now represent excellent value for money, and as the lens coatings were progressively improved as the years progressed, many of the later lenses of this series may have the same coatings as the later MC models. Certainly the optical formula of many of these lenses was unchanged in the late MC versions and even the early MD versions. Accordingly, it is possible to make considerable savings on some expensive lenses through a willingness to consider these early MC Series lenses as an alternative.
  
 
 
 
 
   
The magnificent 24mm f/2.8 VFC (Variable Field Curvature). This lens is typical of the late MC Rokkor era, with the solid steel lens mount (visible as a silver ring at the base of the lens) and the rubber waffle grip.
    
 
These two categories have been joined together, as they are principally the same, except in a minor cosmetic issue. The main changes implemented in the Typical MC Rokkor Series was the introduction of a rubber focusing ring, as opposed to the previous milled metal ring. This was accompanied by a complete redesign of the cosmetic appearance of the lenses, including the replacement of the white metal aperture ring with a black painted ring. As a general rule, coatings were improved from the earlier MC series, but the optical formulas were generally unchanged. In fact, the coatings on these lenses were progressively improved throughout their life, and the later MC models are understood to have coatings very similar to the MD models.

In line with Minolta’s practice of labeling products differently in different markets, the lenses were labeled “Rokkor-X” in the North American market, and “Rokkor” throughout the rest of the world. It is noted that apart from this minor cosmetic change there is no difference between the Rokkor and Rokkor-X version of the same lens.

The difference between the two categories (Typical MC Rokkor and Late MC Rokkor) is generally the discontinuation of the two letter code on the front of the lens. This code designated the number of groups and elements within a lens, with details as follows:

First Letter (no. of groups): T=3; Q=4; P=5; H=6; S=7; O=8; N=9.
Second Letter (no. of elements): C=3; D=4; E=5; F=6; G=7; H=8; I=9; J=10; K=11; L=12.

For example, the 58mm f/1.2 MC Rokkor - PG contained 7 elements in 5 groups. The late MC lenses (3rd MC generation) discontinued this practice.

While the differences between the 2nd and 3rd generations were principally the removal of the two letter lens code, some lens designs were altered during this period. For example, the early MC lenses which featured a depth of field preview button had this feature removed in the later designs, and the 135mm lenses and 200mm lenses were totally redesigned during this era. Additionally, some designs such as the 24mm f/2.8 VFC and the 17mm f/4 were only introduced in the 3rd generation.

Coatings on the MC 2nd and 3rd generation lenses are generally better than those on the earlier 1st generation lenses. However, this is a generalisation because the coatings were undergoing continual development during this period, and accordingly the break from “old” coatings to “new” coatings was progressive, and it is actually likely that there were multiple improvements throughout this period. That said, by the end of the MC series lenses, the coatings were exceptionally advanced , and consisted of multiple layers on both surfaces of all lens elements, giving less flare, better contrast, and rich true colours.

These lenses are generally magnificent examples of the lens maker’s art. With incredible build quality, even in the less expensive models, they make an excellent choice for the keen photographer, and given they are normally about 20% cheaper than their MD Series counterparts, they make good financial sense as well.

 
     
 
 
 
 
   
The 100mm f/3.5 MD Macro Rokkor-X is an example of an earlier MC design that underwent little change when it was converted to MD format. This lens was subsequently superceded by the 100mm f/4 MD Macro lens at the start of the MD 2nd Generation. It is noted that this is one of the lenses that was only offered in MC format for some time after the release of the XD Series.
   
 
With the introduction of the XD series bodies with their “final check” metering system and shutter priority, Minolta released a new range of “MD” lenses. These lenses naturally had the same mount as the previous MC series lenses, but incorporated some changes from the MC lenses which facilitated their operation with the new bodies.

 
 

The minimum aperture dectection lever on a XD11

  
The most obvious change was the addition of a new tab at the rear of the lens diaphragm ring, designed to connect with the XD series bodies minimum aperture switch, telling the camera that the aperture selected was the minimum aperture. This was because the XD Series had introduced a new Shutter Priority exposure mode, requiring that the lens be set at its minimum aperture for correct operation. It is noted that both the XD Series and X-700 cameras will, in fact, work in Shutter Priority mode and Program mode respectively without being set to minimum aperture. However, for full operation, including correct viewfinder displays, the activation of the MD coupling lug is required.
 
         
 
 
   
This shot demonstrates graphically the size differences between late MC lenses and their MD equivalents. Both of these lenses are 50mm f/1.4, but the MD version is considerably smaller and lighter.
    
 
The reason for the selection of the term “MD” for the lenses has been subject to some speculation, but it is now generally accepted that it stands for “Minimum Diaphragm”, in recognition of this change.

The second and less obvious change to the lenses was the introduction of the new lighter weight “dynamically balanced” aperture blades in the MD series, a design purportedly enabling fractionally faster stop-down of the lens. This change was made in recognition of the XD Series “final check” metering system, a new innovation that actually measured the light transmission following the stop down of the lens, in the fraction of a second before the shutter was opened, and based the exposure on this reading. Minolta was concerned that given the slightly slower stop down of the MC series lenses (due to the heavier aperture blades) would result in the final check metering being made as the aperture blades were still moving, hence giving an incorrect reading

The MD first generation lenses are highly sought after for their combination of excellent coatings and high quality construction. As most of the lenses featured 55mm filter threads, they are also convenient for photographers who seek to carry only one size filter.

 
     
 
 
 
 
   
The outstanding 85mm f/2 was a new design introduced with the MD second generation, replacing the venerable 85mm f/1.7. More compact than it's predecessor and with a 49mm filter thread, it exemplifies the changes introduced in this era.
    
 
Early in the production of the MD series of lenses Minolta redesigned many lenses, making them lighter and more compact than previously was the case. This resulted in the creation of a new filter thread size, being 49mm. Some of the lenses redesigned to save weight, and presumably to reduce cost of construction, include all of the 50mm lenses, the 28mm f/3.5 and f/2.8, the 35mm f/1.8 and f/2.8, the 100mm f/2.5 and the 135mm f/3.5. Additionally, the 100mm f/3.5 Macro was discontinued in favour of a lighter weight f/4 model, and the famous 85mm f/1.7 was replaced by a sparkling new design, the 85mm f/2, with outstanding sharpness. Some completely new lenses were also introduced during this period, including the outstanding 200mm f/2.8, and the 85mm f/2.8 Varisoft variable soft focus portrait lens. The company also discontinued their legendary 58mm f/1.2 in favour of the new 50mm f/1.2, which while an excellent performer, has never achieved the popularity of the 58mm version.

The other noticeable change in this era was the replacement on many of the new designs of the metal aperture ring with a black plastic ring, presumably to save weight and costs. While some of the 1st generation lenses had always had plastic aperture rings, this now progressed to most of the new models, and over time other lenses that were not redesigned also received new plastic aperture rings. Despite these minor changes, these lenses are still excellent choices, boasting very good quality of manufacture and outstanding optics. In fact, some of these lenses have proven to be better performers than their previous counterparts, including the new 85mm f/2 (previously the 85mm f/1.7).

  
 
 
 
 
   
Newly introduced for the MD 3rd generation, the 135mm f/2 is an incredible lens, and weighing in at 725g it is one big hunk o' glass. Very rare and highly sought after, this is a lens to show people who claim Minolta never made glass for professionals.
    
 
With the release of the X-700 body, many of the lenses were subject to change again. First and most obvious was the placement of the MD aperture lock on the aperture ring of all of the lenses. This was designed to ensure that when shooting in program mode on the X-700 the lens would not switch from minimum aperture. A skeptic may say that this was a change designed for the general consumer rather than the serious photographer, however there is no doubt that part of the reason for the incredible success of the X-700 was the fact that it was the first “serious” camera which could be used by an absolute beginner with no knowledge of photography whatsoever.

The “MD Lock” as it is commonly known was a part of that success, as a beginner would simply keep this engaged with the camera switched to “Program” and they could be confident of excellent shots. However, the creation of the MD lock was not the only change, and in fact the MD 3rd generation lenses incorporated the most significant changes yet implemented to the Minolta lens lineup.

  
 
 
   
This photo demonstrates some of the differences introduced with the MD 3rd generation. Note the new program lock switch, the changed rubber waffle, and the different coloured focus scale lettering. Both lenses are the 28mm f/2.8.
    
 
Firstly, many of the lenses were again redesigned to reduce weight and size, and the amount of plastic in the lenses increased phenomenally. This included the front plate (around the actual lens) and many of the internal parts. It has been contended that this was partly to ensure that they balanced well with the lighter weight X-700, however given the X-700 at 505g was only 55g lighter than its predecessor the XD11, this argument is considered to hold little water. It is considered much more likely that given the X-700 was squarely targeted at the consumer, it was considered necessary to make cost saving changes in order to keep the price of the lenses down, and competitive. The significant increase in sales for third party lens manufacturers throughout the late 1970’s probably also drove these changes. Lenses to change filter thread size from 55mm to 49mm at this time included the excellent 24mm f/2.8 and the 28mm f/2.

The cosmetics of the lenses changed also during this period, with the colour of the feet scale on the focus ring changing from green to orange/yellow, and the lens designation moving from the right side of the aperture scale, to the left. The rubber on the focus ring also changed, with the number of ribs per inch increasing. Additionally, rather than screw in hoods the lenses now used clip-on hoods that were seated in a shallow groove next to the end of the lens. These hoods were either plastic ( for wide angle and normal lenses) or metal with plastic locking lugs (the telephoto hoods).

 
 

Here you can see the focus assist post on the rear of this 50mm f/1.7 MD 3rd generation lens.

  
The final change that occurred late in the MD Series was the introduction of the mysterious extra post at the rear of the lens, next to the stop down post. This post is designed to work with the focus confirmation system of the X-600, a camera produced at the very end of Minolta’s manual focus product development, of which only 10,000 were ever released.
 
 

The exact location of the post varies depending upon the maximum aperture of the lens concerned, with faster lenses having the post further away from the stop down lever than slower lenses. The location of the post enables the X-600 body to determine the maximum aperture through theuse of a lever inside the body, and based upon whether the speed of the lens is faster or slower than f/2.8, the camera chooses which of its two focus assist sensors to use. Interestingly, the focus system still works with older lenses, albeit not as effectively.

While these comments remain accurate for the vast majority of Minolta lenses, some of the most expensive models did not incorporate the cost saving measures incorporated into most of the MD 3rd generation lenses. For example, the 16mm f/2.8 Fisheye, while being a new design late in the MD 2nd generation series, retained a metal aperture ring instead of a plastic ring. Accordingly, we can assume that for some "Professional" standard lenses a higher build quality was retained. Also, some lenses changed hardly at all with the switch to plain MD labelling. For example, the Varisoft 85mm f/2.8 soft-focus lens changed it's nomenclature from "Varisoft Rokkor" to plain "Varisoft", but that was the only change implemented. None of the other 3rd Generation cosmetic changes (eg. the yellow feet scale on the focusing ring) were implemented. One can speculate that this was due to the cost-effectiveness of implementing such changes on low volume lenses, or simply that for some of these lenses Minolta retained large stocks which were to be exhausted prior to the new changes being implemented. Other lenses not to be changed for the MD 3rd generation included the 250mm and 500mm mirror lenses, the 300mm f/5.6 and the 600mm f/6.3 Tele Rokkor.

With respect to what to get, that really comes down to personal preference. Many photographers prefer the early MD Rokkor or Rokkor-X lenses, which had the most advanced coatings of the various series, but were yet to incorporate the cost and weight saving plastic components that were incorporated in many of the later MD series lenses. Others prefer the MD third generation lenses because they are so much smaller and lighter to carry. Whichever you choose you can be guaranteed of great optical performance.