Review: Minolta AF 600mm f/4 Apo G

1. Introduction

This lens is part of the Minolta AF G – Series that are Minolta’s high performance class optics. Here is what Minolta says about these lenses: “They have the best specifications, feature special advanced technology, and offer the best image quality of all Minolta lenses. The G lenses are designed to meet the high expectations of the most demanding professional and the quality of the image they produce are among the finest in the industry.” 

So lets see if they are correct.




The 600/4 is a favourite among many sport and wildlife photographers. With an angle of view of 4° 10', the 600mm telephoto lens opens up a lot of new possibilities. I have used this lens on a trip to India to photograph tigers and the Asiatic lion. A summary of my thoughts on this lens follows. Remember, this is a subjective review and your opinions might be different. I have only evaluated one lens and sample variations might occur. Anyway I hope you find it useful.

2. Different versions

First of all you should be aware of the following. There are two different versions of this lens. The first was released in 1986 and the second in 1988. Optically the two versions are the same, but the redesigned ’88 version, called the G version, features a faster focusing gear and a new IC ROM to enable faster focusing with the i, xi and si series cameras. External changes include two AF lock/lens function buttons and “High Speed AF Apo 600mm” decal on lens shade. There was possible to have the old version upgraded so that it is equal to the G version except for the focus hold buttons but I am not sure if Minolta still does this. 

The three possible versions of the 600mm/4.0 are: 
  o  The first Apo version: slow auto focus, no AF stop button 
  o  The upgraded Apo version: fast auto focus, no AF stop button. 
  o  The second G – Series version: fast auto focus, AF stop button and ‘High Speed AF Apo 600mm' decal. 

The lens featured in this review is the second version with the focus hold buttons.

The difference between the original version and the G version: 
The G versions have a different IC rom and gear that speed up the AF with 33%. It also has two focus hold buttons located on the barrel. There are some physical differences between the versions (don’t know what, except the focus hold buttons). Glass is the same though. "G" is an attempt at marketing. It is possible to have the original version upgraded (this has been done since the G version was introduced in 1988). The lens will get the new IC and gear but not the focus hold buttons. Minolta may not have the parts to do this anymore. Also, I understand that parts for the original are starting to get scarce and service for it may not be possible in the near future. The price for the upgrade is about $300. 

3. Teleconverters

Performance with converters: 
If used with the old converter, upgraded or new lenses will focus faster. If an old lens is used with new, type II converter, it focuses slowest. 

Differences between the original Minolta tele converters and the Mk II version: 
The old converter models focus 30% faster than the converter model IIs. This is because the high-speed lenses, with converters focused too fast for the pre-i series cameras. So Minolta slowed down the teleconverters. The old 1.4x converter has a 1:1 gear ratio, the Mark II a 1:2 reduction (for the 2x converters the numbers are 1:2 and 1:4 reduction ratio). Both work with old and new lenses, however Mark II plus slow lens gives very slow AF and old TC with fast lens sometimes overshoots or hunts. Optically the different converters are the same. The original converters can no longer be serviced, Minolta USA recommend not purchasing them for any application. That said, the new and upgraded lenses focused faster with the original converter. Original lenses not upgraded focused slowest with the Type II converters. Minolta Japan has not concerned itself as it only deals with current matters. Minolta USA no longer has old style converters around so they can't test one way or another. As they can no longer service the older items, they no longer consider them an issue. NB!! All the above information is obtained directly from or confirmed by Minolta USA. 

4. Lens data
  • Focal Length: 600mm
  • Filter diameter: 42mm drop-in filter
  • Hood Mount: Retractable sliding hood.
  • Dimensions: 169mm x 449mm (diameter x length)
  • Weight: 5500g
  • Aperture:
    • Largest: f/4.0
    • Smallest: f/32
    • Diaphragm Blades: 9 curved aperture blades.
  • Focusing:
    • Method: Internal focusing.
    • Minimum distance: 6.0m
    • Maximum magnification: 0.11X
    • Focus range limiter and two focus hold buttons
  • Optics:
    • Construction: 10 elements (2 AD glass elements)
                             9 groups
    • Angle of view: 4° 10’
With the f/4 aperture you can blur the background 
to make the subject stand out.
Common Kingfisher, Bandhavgarh NP, India.
Minolta Dynax 9 with Minolta 600mm f/4 Apo G lens with Minolta 2x Apo Teleconverter
(Photo © Marcus Karlsen)

5. Appearance and Handling

The design of the lens dates back to 1988 and consists of 10 elements in 9 groups, including 2 expensive AD glass elements to give the lens a tight control on the ever-present chromatic aberrations. This assures high quality and less trouble with colour fringing. The filter thread on the front of the lens is 169 mm and a big and heavy clear protective filter comes with the lens together with a hard case. The clear filter should always be used to protect the front element of the lens. Other filters can be used in the 42mm drop in filter holder. A set of five colour filters (1B, ND4X, Y52, O56, R60) is supplied with the lens. A dedicated polarizing filter and A12, B12 filters are also available but sold separately. 

The customary golden ring, designating a G construction, is placed at the front end and a tiny read-out window for the distance scale with IR focusing index and depth-of-field indications are placed next to the two AF-lock buttons. The lens barrel itself has a smooth white paint finish, which looks nice but unfortunately does not withstand wear that good. The lens itself is very well built with a metal barrel and mount.

The hood is permanently attached to the lens. When you are not using the lens, just turn the hood a little and it will loosen and slide down the lens barrel making the lens easier to store. The hood is shorter than on similar lenses from other manufacturers but it works fine on this lens. The design makes the size of the lens smaller and it is easy and fast to pull out and fasten the hood. The inside of the hood is covered with black velvet to eliminate reflections and the front has a rubber edge for protection.

The lens has a solidly built tripod collar with a big handle for carrying this heavy lens. It is not detachable but that is not a big problem, as the lens always should be used on a sturdy tripod or on a beanbag.

The focusing ring is slightly recessed in the barrel with a metal cover that you can slide over it. This prevents you from interfering with its movement in auto focus mode when the focusing ring turns. The focusing ring is a little thin when using the lens in manual focus but it is not a big problem. The near focusing range of the lens is 6.0m. The lens also has a step less focus range limiter. By loosening a small knob on the lens you can turn the focus limiter left or right and thus limit the focus range on the far or near side. To allow the lens to use the entire focus range again, just loosen the knob and the focusing barrel can move freely through the entire range. The focus range limiter is very useful on a lens like this. By narrowing the focus range the lens locks focus faster as it does not have to cover the whole range from 6.0m to infinity.

The lens focuses by moving the lens elements by a shaft. A motor in the camera drives the shaft, making the focusing speed dependent on which camera model the lens is coupled with. The lens is also compatible with Minoltas own teleconverters as well as all third party converters with Minolta A mount. The lens will auto focus with the Minolta AF 1.4x teleconverter II Apo, although a little slower because of the reduction gearing in the TC and light loss. With the AF 2.0x teleconverter Apo auto focus is not available because of light loss and you have to use manual focus.

In total I find the focusing speed of the lens good. The problem is not the auto focus speed, on the Dynax 9 the lens focuses just as fast as the Canon 70-200mm f/2.8 IS L USM on the Canon EOS 10D. However the camera often hunts back and forth before it locks on to the subject, the Canon system will not do this. On the bright side the Minolta system focuses better in low light.

This lens would probably benefit from SSM focusing to stop the hunting of the focus system and to lower the audible noise.

6. Optical Performance

Different wavelengths of light come into focus at different planes. This effect is know as Chromatic aberration and can cause a "rainbow" halo around points of light and reduced sharpness. "Standard" achromatic telephotos are corrected to bring the red and blue components into focus at the film plane. The Anomalous Dispersion (AD) glass, used in the first two elements of the lens, virtually eliminates the effects of lateral and longitudinal chromatic aberration, providing increased sharpness and extremely accurate colour rendition.

I have tried to summarize my findings when shooting a resolution chart with the lens to test its optical quality in the tables below. The ratings are as follows:

     *      Very poor 
    **     Poor 
   ***    Ok 
  ****   Good 
 *****  Very Good 


600mm f/4.0

f-stop

Sharpness centre

Sharpness middle

Sharpness corner

Contrast

Distortion

Vignetting

Colour

4

*****

*****

****

****

no

no

neutral

5.6

*****

*****

****

*****

no

no

neutral

8

*****

*****

*****

*****

no

no

neutral

16

*****

*****

*****

*****

no

no

neutral

Overall the AF 600mm f/4.0 Apo G lens delivers excellent image quality.

Chromatic aberration was virtually absent from any of the test images at any aperture setting. This in its turn resulted in a high-contrast rendition with vibrantly saturated colours, typical of the Minolta G optics.

Illumination is even across the entire frame at f/4.0, so corner light fall-off is absolutely negligible. Geometric distortion is also non-existent.

 

The graph 
The graph shows MTF in percent for the two line frequencies of 10 lp/mm and 30 lp/mm, from the centre of the image (shown at left) all the way to the corner (shown at right). The bold lines represent sagital MTF (lp/mm aligned like the spokes in a wheel). The thin lines represent tangential MTF (lp/mm arranged like the rim of a wheel, at right angles to sagital lines). On the scale at the bottom 0 represents the centre of the image (on axis), 3 represents 3 mm from the centre, and 21 represents 21 mm from the centre, or the very corner of a 35 mm-film image. Separate lines show results at f8 and full aperture. This is Minoltas own MTF graph for this lens.

7. When the image is out of focus

The word Bokeh is of Japanese origin and relates to the fashion in which the out-of-focus areas of the image are rendered. A sharply focused subject set against a pleasingly silky smooth background characterizes a good bokeh. The transition from in-focus to out-of-focus should occur gradually. A large number of aperture blades give a more circular opening when the lens is stopped down, but this in itself is not sufficient to give a good bokeh. Another feature of the lens that affects Bokeh is the degree of spherical aberration correction. Spherical aberration is when the rays of light from the middle and from the outside edges of a lens do not focus to exactly the same point.

In technical terms there're two main factors for a good bokeh: 

1. Circular aperture 
Defocused background highlights take the shape of the diaphragm in wide- aperture portraits shots. The 7 and 9 blade apertures found in some of the Minolta lenses are specially designed to provide a circular opening at widest apertures. A circular aperture produces softer, more natural looking backgrounds at wider apertures than a lens having a standard 5, 6, 7 or 9 bladed aperture. 

2. A minimal difference between the sagitally (centre to edge) and tangentially (around the centre) resolution of the lens. The more these two types of resolution differ the less symmetrical are the out-of-focus highlights.


Asiatic lion, Gir Sanctuary, India.
Minolta Dynax 9 with Minolta 600mm f/4 Apo G lens.
(Photo © Marcus Karlsen)
The 600mm f/4.0 Apo G have a very pleasing image rendition. The bokeh gives the images an almost magic look.

The image of the Asiatic lioness to the left is one of my favourites from the trip to India. Look at the way the out of focus areas are rendered. The smooth transaction between the highlights and the darker areas gives the image a magic, almost dreamy look. Because of the small size of the image on this web page it is not so easy to see,  but on full screen or printed out it is simply spectacular.

8. Flare and ghosting

What causes flare

Since light reflects off glass surfaces, lens flare usually increases with the number of glass elements in the lens. The problem is compounded with backlit subjects. 

With the 600mm f/4.0 Apo G lens flare and ghosting has not been a problem.

9. Summary and Conclusions

This high quality lens is excellent optically and has fast auto focus. The focus stop buttons on the lens barrel are very useful. In combination with the Minolta Apo teleconverters this lens is the ideal lens for wildlife and sports. 

Pros 
   o Excellent optical performance, even with dedicated converters 
   o Very good bokeh 
   o Good auto focus
   o Image stabilizer with the Dynax 7 Digital (built into the camera body)

Cons 
   o Auto focus is a little noisy and has a tendency to hunt in some situations. 
   o No image stabilizer with film body (with the Dynax 7 Digital stabilization is in the camera body)


The lens does not have image stabilization as this feature will be incorporated into Minoltas new digital SLRs. This should take care of the image stabilizer issue for all digital shooters.

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