Review: Minolta AF 300mm f/2.8 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 300/2.8 lens is a favourite among many sport and wildlife photographers. With an angle of view of 8 10', the 300mm telephoto lens gives magnification of 5X over a normal 50mm focal length. Still for wildlife it is often too short and have to be used together with converters. However the f/2.8 maximum aperture is a big advantage for freezing action in low light. I have used this lens extensively here in Norway and on two trips to Africa and a summary of my thoughts on this lens follows. Remember, this is a subjective review and your opinions might be different. I have also just 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 1985 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 300mm” 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 300mm f/2.8 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 300mm' decal. 

In addition to this Minolta have released a 300mm f/2.8 SSM Apo G lens that is a total redesign of the lens with even better optics and faster auto focus, at least according to Minolta. The new lens is one of currently only two Minolta lenses to feature SSM (Super Sonic Motor) auto focus. This is the equivalent to Canons USM and Nikons Silent Wave and means a motor in the lens drives the auto focus and not a motor in the camera body as on the other Minolta lenses. Thus the auto focus is silent and faster. I have not tried the lens myself yet but I hope to do so real soon.

The lens featured in this review is the second G - version.

The difference between the original version and the G version according to Minolta: 
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 teleconverters 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. 


Black Rhino, Etosha National Park, Namibia
Minolta Dynax 9 with Minolta 300mm f/2.8 Apo G lens 
with Minolta 2x Apo Teleconverter
(Photo © Marcus Karlsen)
I often find the 300mm focal range too short for wildlife and have to multiply with a 2x converter. The optical quality of the Minolta lens allows this with still very good image quality.

4. Lens data

  • Focal Length: 300mm
  • Filter diameter: 42mm drop-in filter
  • Hood Mount: Retractable sliding hood.
  • Dimensions: 128mm x 238.5mm (diameter x length)
  • Weight: 2480g
  • Aperture:
    • Largest: f/2.8
    • Smallest: f/32
    • Diaphragm Blades: 9 curved aperture blades.
  • Focusing:
    • Method: Internal focusing.
    • Minimum distance: 2.5m
    • Maximum magnification: 0.14X
    • Focus range limiter and two focus hold buttons
  • Optics:
    • Construction: 11 elements (2 AD glass elements)
                              9 groups
    • Angle of view: 8° 10’
  Field of view for different focal lengths

5. Appearance and Handling

The design of the lens dates back to 1988 and consists of 11 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 114 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. For other filters the lens uses a 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 of the lens and a tiny read-out window for the distance scale with depth-of-field indications is 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 and comes off quite easily. The lens itself is much better built, with a metal barrel and a metal mount, and can take a lot of abuse. 

The hood is permanently attached to the lens. It has a turn and slide design which means that 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 a lot smaller and 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. The collar is not detachable but that is not a big problem, as it is not protruding much from the lens. A good and compact design.

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 I don't find it to be a problem. The near focusing range of the lens is 2.5m. 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 this lens. By narrowing the focus range the lens locks focus faster as it does not have to cover the whole range from 2.5m to infinity. I use this feature quite often, setting the focus range from about 8m to infinity. 

The lens uses an internal-focusing optical design to enhance high-speed auto focusing. Since focus is adjusted by moving the smaller, lighter central elements rather than the heavier front elements, auto focusing is faster and more precise. A shaft moves these central elements so the image is focused on the film plane. A motor in the camera drives the shaft and makes the focusing speed dependent on which camera model the lens is coupled with. I have tried the lens on the Minolta Dynax 700si and the Minolta Dynax 9. On the Dynax 9 the auto focus is very fast, on the 700si a little slower. Some hunting occurs but not so much that it is a problem. 

The lens is compatible with Minoltas own teleconverters as well as all third party converters with Minolta A mount. With the Minolta AF 1.4x teleconverter II Apo the auto focus is a little slower because of the reduction gearing in the TC and light loss but it is still good. With the AF 2.0x teleconverter Apo the auto focus is so slow and hunting so much that it is useless and it is better to switch to manual focus. With the 2.0x converter the lens might also start to micro hunt. This means the auto focus system cannot decide on what to focus on and the camera will make tiny adjustments to the focus all the time. This is especially a problem with the 700si in low light. With the Dynax 9 the problem is almost gone. 

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 noise. The focusing with a 2.0x converter would probably be better as well. Minolta have released a 300mm f/2.8 SSM Apo G lens that should have better auto focus but I have not seen or tried this lens so I cannot say anything about it.

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 


300mm f/2.8 Apo G

f-stop

Sharpness centre

Sharpness middle

Sharpness corner

Contrast

Distortion

Vignetting

Colour

2.8

****

****

****

****

Slight pincushion

no

neutral

4

*****

****

****

****

Slight pincushion

no

neutral

5.6

*****

*****

****

*****

Slight pincushion

no

neutral

8

*****

*****

*****

*****

Slight pincushion

no

neutral

11

*****

*****

*****

*****

Slight pincushion  

no

neutral

16

*****

*****

*****

*****

Slight pincushion

no

neutral


300mm f/2.8 Apo G with  1.4x Apo II Tele converter

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


300mm f/2.8 Apo G with 2.0x Apo Tele converter

f-stop

Sharpness centre

Sharpness middle

Sharpness corner

Contrast

Distortion

Vignetting

Colour

5.6

****

***

***

***

no

no

neutral

8

*****

*****

*****

*****

no

no

neutral

16

*****

*****

*****

****

no

no

neutral

Overall the AF 300mm f/2.8 Apo G lens delivers a very good 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.

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.

Illumination is even across the entire frame at f/2.8, so corner light fall-off is absolutely negligible. Geometric distortion is also no existent.

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.
Be careful when you have unfocused highlights in the background as these are not rendered very nicely by the lens. You can see they are darker in the middle than at the rim. It should have been the other way with a lighter centre and darker edges.

Minolta Dynax 9 with Minolta 300mm f/2.8 Apo G lens with Minolta 2x Teleconverter. Velvia 50, 1/250 @ f/5.6
(Photo © Marcus Karlsen)

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. 

On the 300mm f/2.8 Apo G lens the aperture is designed to give circular aperture down to f/5.6, but as the images below show that is not the case.

f/2.8 f/4 f/5.6 f/8

2. Good spherical aberration correction
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.


Olive Baboon, Lake Manyara National Park, Tanzania
Minolta Dynax 9 with Minolta 300mm f/2.8 Apo G lens 
Sensia 100, 1/100 @ f/2.8, -0.5 exposure compensation 
(Photo © Marcus Karlsen)
The Minolta 300mm f/2.8 Apo G have a pleasing image rendition if you avoid the brightest highlights in the background. Not quite as good as the 200mm f/2.8 Apo G or the 600mm f/4 Apo G, but close.

8. Flare and ghosting

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 300mm f/2.8 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 f/2.8 max aperture 
   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 Slow auto focus with converters 
   o No image stabilizer with film body (with the Dynax 7 Digital stabilization is in the camera body) 

Minolta has now released a new 300mm f/2.8 lens with SSM focusing, better optics and a detachable tripod collar. The lens does not have image stabilization as this feature is incorporated into Minoltas digital SLRs. This lens should take care of all the cons of the earlier lens except image stabilization for film shooters.

10. Magazine lens tests

  • German magazine Color Foto test results 
    19 out of 30 on sharpness
    27 out of 30 on contrast
    17 out of 20 on centering
    8 out of 10 on distortion
    8 out of 10 on vignetting
    That makes it 79 out of 100 total and that is 5 points behind the new Minolta 300mm f/2.8 Apo G (D) SSM lens.
  • French magazine Chasseur d'Images test results on the Dynax/Maxxum 5D
    Vignetting 4/5
    Chromatic abberation 4/5
    Distortion 5/5
    Sharpness 4/5
    Total score 4/5

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