Rodagon 28mm f/2.8 lens
The Rodagon 28mm f/2.8 lens (R2828) is sold today by Qioptiq under the Linos brand name, without any Rodenstock branding. This is the smaller all metal industrial body with a M32.5 x 0.5 thread mount replacing the older f/4 version in the plastic enlarger lens body with M39 mount. The Rodagon 28mm lenses don’t come up on the used market very and prices are often way too high for what these lenses are, $100+ for the f/4 version, the f/2.8 version in this test can be very hard to find used. In February 2022 I found two of these lenses by pure luck paid less than $50 complete with case and M32.5 - M45 step-down adapters. In 2016 I owned a copy of this lens but unfortunately I sold the lens, and all of my other 28mm and 35mm enlarger lenses before I had any idea how to use them properly for photomacrography!
Optimum Magnification
The R2828 uses an asymmetrical optical layout (similar to an enlarging lens) designed with an optimum conjugate, a magnification factor at which the lens performs at it's best, stopped down two stops down from maximum. That factor is somewhere in the middle of a range in which the lens is designed to produce the best image quality.
Rodagon 28mm f2.8
Optimum range: 1:4 - 1:20x reduction normally mounted and 4:1 - 20:1x magnification in reverse mount
Optimum: 1:10x reduction normally mounted and 10:1x magnification in reverse
This lens will perform best in a stacked configuration thanks to it’s optimized range. Stacking lenses, also called coupling lenses, is a technique where you mount a lens at the end of a telephoto lens in reverse. With both lenses set to infinity focus there is no loss of light due to extension. Together the combination has the potential to resolve more than either of the lenses setup for close-focus with extension.
For this test I will compare the performance at 4x with extension only and 4x magnification using a stacked lens configuration.
ABOUT THIS TEST
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FIT AND FINISH
The R2828 is in an all-metal body without any plastics like the f/4 enlarger version. This gives the lens a nice tactile feel. The only let down about the R2828 is the quality of the name decal, its not even a high quality, you can see small bits of adhesive all around the edges of the sticker.
PROS AND CONS
What I really like:
Very compact size
All-metal body
Fast f/2.8 aperture
What I don’t like
Lens name decal
Limited to APS-C sensor coverage
Hard to find on the used market
Corner image quality
Lens groups are installed into iris mount no in cells
Rodagon 28mm f/2.8 lens
RODAGON 28 TECHNICAL SPECIFICATIONS
Rodagon 2.8/28
Lens applications: Machine vision quality control
Part number: 0701-389-000-20
Focal Length at infinity: 27.7mm
Nominal maximum Aperture: f/2.8
Aperture Range: f/2.8 - f/16
Mounting threads: M32.5 x 0.5
Accessory threads: M30.5 x 0.5
Barrel type: Metal
Optics: 6 elements in 4 groups
Sensor pixel pitch: 7µm
Spectral range: 400-750 nm
Design includes sensor cover glass: no
Iris design: 6 blades
Magnification range: 0.05x (0.2x..0.03x)
Compatible sensor size: 32mm image circle (this figure is at the rated magnification and mounting)
Weight: 60 g
Dimensions: ⌀ 31 x 40mm
Current Retail Price: $852 USD (2019: $740. USD)
Typical used price: $150-200. Asking prices are often too high for this lens, don’t over pay.
Lens source: made in Germany
Note:
There are at least types of the Rodagon 28 that you see on the used market.
Rodagon 28mm f/4 all-metal industrial body M32.5 x 0.5 mount. Sold as a process lens. Discontinued.
Rodagon 28mm f/2.8 all-metal industrial body M32.5 x 0.5 mount, current model
Rogagon 28mm f/4 plastic enlarger lens body 39mm Leica thread mount. Discontinued.
3.2X stacked TEST: RODAGON 28MM VS COMPONON 28MM
Unfortunately the Rodagon image circle was not large enough to cover a full frame sensor but this is not due to the 32mm image circle the lens is rated. The Componon is rated to cover 30mm and it covers a full frame sensor perfectly. The problem is the front lens shroud depth limits how close the lens face can be positioned to the Mejiro main lens, causes hard corner shading. The Componon front element can be positioned much closer to the main lens than the Rodagon.
TEST SETUP
Front lens: Rodagon 2.8/28 lens reverse mounted
Rear lens: Mejiro 5.6/90 line scan lens normally mounted focused at infinity
Stacked lens nominal aperture: f/4.0
Stacked lens effective aperture: f/12.8
Front lens: Schneider Kreuznach Componon 2.8/28 Makro Iris lens reverse mounted
Rear lens: Mejiro 5.6/90 line scan lens normally mounted focused at infinity
Stacked lens nominal aperture: f/3.3
Stacked lens effective aperture: f/10.5
The Componon 28mm is one of my first macro lenses and still years later one of my favorites. They are hard to beat for the price and performance.
Camera: Sony α6300, model # ILCE-6300, also known as: A6300
Sensor size: APS-C 23.5 × 15.6 mm. 28.21 mm diagonal. 3.92 micron sensor pitch
Flash: Godox TT350s wireless flash x 2 with one Godox X1s 2.4G wireless flash transmitter
Vertical stand: Nikon MM-11 with a Nikon focus block
For this test I ran a stack of images in 4 micron steps for each aperture. The sharpest frame was then chosen using Photoshop at 100% actual pixel view. Separate images were selected for center, edge, and corner if needed. Each image was processed in PS CC with identical settings with all noise reduction and lens correction turned off, all settings were zeroed out (true zero) and the same settings were used for all of the images.
3.2X TEST: 100% VIEW CENTER CROPS
Click on the image below to see a larger version of the image below with a dark background in a lightbox viewer. Or you can always right click, or two-finger press, and select Open in a New Tab or New Window from the menu. You can also right click, or two-finger press, and select Save Image As to save and view the image full size.
The Rodagon is sharp at f/4 but there is quite a bit of pink fringing see the micro-numbers 235 in the lower left of the frame. The Componon is sharper, without any CAs.
3.2X TEST: 100% VIEW Far CORNER CROPS
Click on the image below to see a larger version of the image below with a dark background in a lightbox viewer. Or you can always right click, or two-finger press, and select Open in a New Tab or New Window from the menu. You can also right click, or two-finger press, and select Save Image As to save and view the image full size.
The Rodagon doesnt quite cover the APS-C sensor with a sharp image, the image quality drops away from the center. The Componon is much sharper and the image circle will cover a full frame sensor with quite a bit less CAs.
3.2X TEST RESULTS
The performance of the Rodagon 28mm f/2.8 at 3.2x stacked is about average for an enlarger lens. The Componon 28 has better coverage, sharpness and CA control. A bellows lens or line scan lens would do a better job covering an APS-C and full frame sensor than this lens.
These two lenses are designed for different levels of performance. The Rodagon has elements mounted directly in the iris mount, held in place by retainer rings using passive alignment. Centration errors are higher in this type of setup compared to the Componon that uses lens cells that aligned for best performance and locked in place with cement. So the difference in performance is expected even though the two lenses have similar retail prices there is quite a gap in performance between the two not to mention a huge gap in fit and finish, not just in performance.
For more information on the Componon 28mm f/2.8, follow this link: https://www.closeuphotography.com/schneider-kreuznach-28mm-f2-8-componon-lens
3.2X extension TEST: RODAGON Vs Rodagon
This is a comparison of two Rodagon 28mm f/2.8 copies that I picked up for this test, both focused at 3.2x with extension. There is quite a bit of a performance penalty when comparing these crops to the stacked configuration images above. The one advantage of the extension setup is a flat field where the stacked setup required a different file for the corner crop.
Rodagon 2.8/28 lens reverse mounted
Nominal aperture for this test: f/4.0
Effective aperture at 3.2x: f/16.8
Rodagon 2.8/28 Copy One on Extension
Rodagon 2.8/28 Copy Two on Extension
Copy two seems to look very slightly sharper but with more red fringing than copy one.
Rodagon 2.8/28 Copy One on Extension
Rodagon 2.8/28 Copy Two on Extension
Both R2828 units have quite a bit of image quality fall off in the corners, common for an enlarger lens. This lens does quite a bit better in a stacked setup focused at infinity.
LENS DATA
Note: Rodenstock MTF curves are calculated. According to Rodenstock, “The reality is when you measure MTF curves on the MTF machine with a lens it could have a tolerance of -10 % at the most."
Other 25-30mm Lenses on the Used Market
All the lenses below have been tested at least once.
Minolta 30mm Rokkor CE: Not recommended.
Excessive chromatic aberration problems. Expensive. No front accessory threads.
Minolta E. Rokkor 30mm F4.5 enlarger lens: Not recommended.
Chromatic aberration problems. Poor corners. No filter threads.
Rodenstock Omegaron 25mm f/4 enlarging lens: recommended.
M32.5mm x 0.5mm mount. Sleeper lens. Low cost and decent quality. No filter threads.
Schneider Componon 4/28: Highly recommended.
Excellent image quality. Good used prices online.
Schneider Componon 2.8/28 Machine Vision Lens: Highly recommended.
The highest image quality from any of the 28mm lenses listed here.
Schneider M-Componon 4/28 Macro Lens: Highly recommended.
Great image quality and coverage.
Schneider Xenon 2/28 printing machine lens: Highly recommended.
Amazing image quality but a little hard to find on the used market.
Schneider Xenoplan 2/28 machine vision lens: recommended.
Poor APS-C coverage. Amazing center sharpness. Very recommended for smaller sensors.
Voss 25mm f/3.5 enlarging lens: Not recommended.
Soft in the center with worse corners at f/4-5.6. Very soft at f/3.5.
LINKS FOR MORE INFORMATION:
Current Linos Rodagon 28mm listing on Digikey:
https://www.digikey.com/en/products/detail/excelitas-technologies/0701-389-000-20/11505916?
Current Linos Rodagon 28mm listing on the Qioptiq ( site:
The current Linos Rodagon 2.8/28 Data Sheet:
https://www.qioptiq-shop.com/out/Graphics/en/00123876_0.pdf
Current Qioptiq - Linos Rodagon Lens PDF, note: 28mm Rodagon is listed:
https://www.qioptiq-shop.com/out/Graphics/en/00119141_0.pdf