Achromatic lenses – the „always-with-you“ macro?

DieserBeitragInDeutschI am pretty sure that nowadays only very few people use achromatic lenses if they know them at all. Two of those achromatic lenses manufactured by Minolta Co. Ltd. are sleeping since a long time in one of my photo boxes. Yesterday, while searching for something, I found those achromatic lenses again and …

… and what? My first intention was: „It is about time to get rid off this old stuff and sell it – maybe somebody is interested in it!“. So I took these parts out of the box and thought: „Well, some product pictures and maybe some pictures of the same object shot with and without using the achromatic lenses could support selling them!“ – and I found out something interesting while making the pictures. These are the two achromatic lenses and its technical details first::

DSC01812

Minolta 49mm No. 1 Minolta 55mm No. 2
Optical correction +2,0 Diopt. +3,8 Diopt.
Weight incl. the box 46 g 96 g

Achromatic lens or close-up lens

Before talking about the possible use of the achromatic lenses I would like to write some words about the difference between achromatic lenses and close-up lenses.

Achromatic and close-up lenses have in common that both types are mounted to the front of a regular lens – which is about it for the things in common. Close-up lenses are made of one simple collecting lens. Achromatic lenses are made of a collecting lens and a diffusing lens which partly correct chromatic abberation and therefore produce a much better image quality than close-up lenses.
Source: http://www.elmar-baumann.de/fotografie/lexikon/vorsatzachromat.html

The confusing part is, that both boxes clearly show „CLOSE-UP LENS“, but the results of my research is, that these two lenses are achromatic close-up lenses made of the two mentioned lenses and not simple close-up lenses.
Sources: http://www.sonyuserforum.de/forum/archive/index.php/t-13555.html, https://naturfotografen-forum.de/o129703-Achromaten%20-%20Tabelle%201

Matching lenses

Both Minolta achromatic close-up lenses are from a time, when most lenses had front lenses with smaller diameters like 49 and 55 mm – mainly from the good old celluloid time. The last couple of year I was taking pictures with Sony A-mount and during this period I may had one or two lenses with a matching front lens diameter so that I did not use the achromatic lenses at all – especially not on my travel kit. Now, that I completely moved to E-mount, I found out to my suprise, that I have 6 lenses which are compatible with these achromatic close-up lenses and neither the use of the lens hood nor the use of the front cover is lost. This is the list of matching lenses:

APS-C – sensor (Sony alpha 6000) Fullframe-sensor (Sony alpha 7)
lens ø filter diameter lens ø filter diameter
E 20 mm F2,8 49 mm Sonnar® T* FE 35 mm F2,8 ZA 49 mm
E 35 mm F1,8 OSS 49 mm Sonnar® T* FE 55 mm F1,8 ZA 49 mm
Vario-Tessar® T* E 16 – 70 mm F4 ZA 55 mm FE 28–70 mm F3,5–5,6 OSS 55 mm

Effect

I used a simple setup with a focusing slide to demonstrate the effect using an achromatic lens taking the clock face of a watch – I don’t wear watches since years now – with a diameter of 2.8 cm. Test lenses are Sonnar® T* FE 35 mm F2,8 ZA and FE 28–70 mm F3,5–5,6 OSS at 70mm on the Sony alpha 7.

Sonnar® T* FE 35 mm F2,8 ZA

ohne /without Achromat
ohne / without Achromat
mit /with Achromat 49 No.1 +2 Diopt.
mit / with Achromat 49 No.1 +2 Diopt.

The clock face with 28 mm covers a diameter of 612 pixels on the picture shot without the achromatic lens which is approx. 22 pixels per millimeter:

ohne /without Achromat
ohne / without Achromat

The clock face covers 958 pixels at the diamerter using the Minolta achromatic close-up lens 49 No.1 with +2 Diopter correction which results in approx. 34 pixels per millimeter and an enlargement of factor 1.5. The close distance is reduced by approx. 9 cm:

mit /with Achromat 49 No.1 +2 Diopt.
mit / with Achromat 49 No.1 +2 Diopt.

FE 28–70 mm F3,5–5,6 OSS bei 70mm

ohne / without Achromat
ohne / without Achromat
mit / with Achromat 55 No.2 +3.8 Diopt.
mit / with Achromat 55 No.2 +3.8 Diopt.

Using th FE 28–70 mm F3,5–5,6 OSS without achromatic lens at a focal lenght 70mm the clock face covers a diameter of 979 pixels which is 35 pixels per mm:

ohne / without Achromat
ohne / without Achromat

Using the Minolta achromatic close-up lens 55 No.2 with +3.8 Diopter correction the clock face diameter covers 2150 Pixel which is 77 pixels per mm and results in an enlargement of approx. facter 2.2. The close distance is reduced by approx. 15 cm.

mit / with Achromat 55 No.2 +3.8 Diopt.
mit / with Achromat 55 No.2 +3.8 Diopt.

Verdict

I am suprised about the possibilities using the achromatic close-up lens 55 No. 2 with the FE 28–70 mm F3,5–5,6 OSS. I expect even more sensor coverage using the same achromatic lens on the Sony alpha 6000 in combination with the Vario-Tessar® T* E 16 – 70 mm F4 ZA because of the crop factor – I haven’t tried it yet.

At least, these results kept me from selling the achromatic close-up lenses and they will be in my bag more often on further hiking tours. Of course, they can’t replace a full macro lens like the Venuslens / LAOWA 60mm F2.8 Ultra Macro 2:1, but they are a nice and lightweight alternative in the photo bag to picture smaller objects a bit larger.

Weblinks (german)

http://www.elmar-baumann.de/fotografie/lexikon/nahlinse.html

http://www.elmar-baumann.de/fotografie/lexikon/vorsatzachromat.html

http://www.elmar-baumann.de/cgi-bin/foto/fotocgi

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