When looking for new lenses to buy for my vintage Minolta X-700 or modern Sony NEX, I always search the net for tests and opinions. Most of the time, all I can find is a handful posts in one of the classic camera forums (see links section) with some people praising the lens and others reporting rather mediocre performance. If I’m lucky, someone uploaded low-res test shots done with the lens showing that light may or may not pass through it.
Rarely there are any hard facts or actual objective comparisons of vintage lenses. The main reason for this is obvious: These lenses are not in production anymore and there is no manufacturer promoting them. Therefore, the lenses are harder to come by than new lenses and there is little to no demand for them on the lucrative professional market. This, in terms, leads to the situation that there is little to no market for quality information on the lenses although there may be demand for it among enthusiasts.
One might argue with my reasoning, but in the end, little info is indeed available. Since I am none the less interested in the performance of my acquisitions, I test them myself. Using the ISO 12233-alike lens test chart by Stephen H Westin all lenses that go through my hands are shot adapted to a NEX-5N or 5T. The shots are converted from RAW to lossless PNG using Adobe CameraRaw. For more info on the test conditions and all limitations, have a look at the test setup details. Before interpreting the results, bear in mind that my tests do not comply with ISO 12233 and are not perfect by any means.
The tests are categorized into original Minolta, third party and original Sony lenses. Native E-mount lenses are shot as a benchmark and allow direct comparisons of vintage to modern designs. In my reviews, you will find pixel-level crops from the test charts, as well as general info on the lenses such as build quality, handling, the condition of my copy and a short summary of the optical performance. The summary is subdivided into three sections: A writeup on sharpness, resolution and longitudinal CAs in the plane of focus (haze), a short comment on lateral CAs (color fringes) and info on vignetting, distortion and transmission (T-stop). I try to use a consistent rating system amongst the reviews, primarily for the sharpness/resolution evaluation, which is graded as follows:
The best you could expect from a lens. Even at 200% magnification, contrasty edges are razor sharp. Will lead to moirées on fine structures.
- Very good
Close to excellent in full view. At 200% magnification, contrasty edges may not be razor sharp. Will still lead to moirées on fine structures.
Sharp on first impression, but easy to tell from excellent in full view. Should still be usable for any application you can think of, but it’s not the best you can get. Moirées are less common.
Not quite sharp on first impression. Images with this rating are probably not the best choice for enlarged prints or the usage on 4K screens. Moirées do not appear in these images. Often termed “close to good” in the reviews.
- Mediocre / Soft
Soft at first impression. The most common rating for wide open shots on vintage lenses and not something you want for architecture or landscape photography. Images can still be interesting for other types of photography, though. For example, shots with this rating are usually not problematic when high ISO noise is your main concern or you are looking to shoot a flattering portrait.
Vignetting and distortion are categorized as follow:
Vignetting or distortion with this rating shouldn’t be evident in your photos.
Vignetting or distortion are measurable, but should be irrelevant for practical applications.
Vignetting or distortion are visible and may be disturbing in particular situations.
Vignetting or distortion are very prominent and will be disturbing in daily use.
If you are not quite sure if the 100% crops in the reviews suffice to satisfy your thirst for wisdom, the lossless full-res PNG images of the test chart (about 20 MB each) are available on request. And last but not least, I also create lens correction profiles for the Photoshop lens correction filter from the test charts if I’m particularly interested in that lens.