Copal E18C 40mm 1:4 Industrial Lens
Industrial lenses like the E18C 40mm are usually well corrected and I’ve had good results with this type of lens in the past so this lens has impossible to pass up for only $20 plus shipping. Due to the slow f4 aperture the lens will perform best in a stacked or coupled configuration mounted in reverse on a telephoto lens focused on infinity. It will be very interesting to see how the E18C image quality compares to a popular lens like the Canon MP-E 65, one of the few consumer market lenses still sold today optimized for magnification range beyond 1x.
This lens was purchased at the full price and I did not receive any discount or commission for this post which does not contain any affiliate links, ads or visitor tracking.
Quick Review
Field curvature well corrected
Good CA correction (better than the E18C 35mm at the same magnification)
Consistent sharpness and image quality over the entire frame
All metal barrel, no plastic
Standard 30.5mm x 0.5 filter threads
Covers APS-C
Super compact and weighs only 1 ounce
Impossible to beat $20 price
Copal E18C 40mm 1:4 Industrial Lens
Lens Specifications
Copal E18C 40mm 1:4
Lens type: Industrial lens
Aperture: preset f4
Focal length: 40mm
Barrel Length: 28mm
Barrel diameter: 32mm OD
Chromatic Correction: good
Resolution: good
Designed lens coverage: APS-C
Working Distance: 22mm
Mounting Threads: None.
Filter Mounting Threads: Standard M30.5 x 0.5
Forward or Reverse Mount: Reverse
Country of origin: Japan
Cost used: $20 plus $6 for shipping
Notes: Copal is the Japanese company most famous for making leaf and focal plane shutters, starting out as the Copal Optical Works Co Ltd, and later Copal Co Ltd and finally Nidec-Copal in 1999: https://www.nidec-copal.com/en-Global/
Mounting the E18C lens
This lens is simple and easy to mount using the standard M30.5 x 0.5 filter threads. To mount the lens on the Nikkor 135 lens was simple, the Nikon has 52mm x 0.75 filter threads so a 52mm to 52mm male to male adapter and a 30.5mm to 52mm step up adapter are all thats needed to install the E18C lens.
Copal E18C 40mm 1:4 Industrial Lens stacked on the Nikkor 135mm f3.5 Ai rear lens
STACKED Lenses or extension?
Stacking lenses, also called coupling lenses, is a technique to increase magnification where you mount a longer focal length lens on the camera and a second shorter focal length in reverse and face-to-face on the rear lens which is set to infinity focus. Together the combination has the potential to resolve more than either of the lenses setup for close-focus with extension.
You can predict the maximum possible resolution from a certain lens by using the simple fact that a wider aperture = higher potential resolution. A lens focused by extension only would have an effective aperture using the simple formula, effective aperture = nominal aperture * ( Magnification + 1 ). The effective aperture of a stacked lens using the formula effective aperture = nominal aperture * Magnification. In this case the Copal lens would have an effective aperture of f17 but in a stacked setup the effective aperture is only f/13.6.
Copal E18C 40mm 1:4 Industrial Lens
3.4x test: Canon MP-E 65mm F/2.8 1 - 5 X Macro Lens vs Copal E18c 40mm 1:4 Lens
SETUP
Front lens: Copal E18C 40mm f4
Rear lens: Nikon Nikkor 135mm f/3.5 Ai Lens
Stacked lens effective aperture: f/13.6
MP-E 65 lens effective aperture: f/14.0
The Canon MP-E 65 was tested here at f3.2, its sharpest aperture, f2.8 was worse due to increased chromatic aberrations and f4 was noticeably softer.
The Nikkor 135mm f/3.5 Ai is a surprisingly good tube lens and an excellent value. A comparison of tube lens image quality including the Nikkor 135mm f/3.5 Ai is available here on Closeuphotography.com: https://www.closeuphotography.com/tube-lens-test
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 a stack of images was made with 10 micron steps. The sharpest frame was then chosen using Photoshop at 100% actual pixel view. Separate images were selected for center, edge, and corner for both lenses. 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. All of the images shown here are single files.
Copal E18C 2500 PIXEL IMAGE SAMPLE
Click on the image below to view a larger version in a Lightbox viewer, the size of the image sent to your device is based on the screen size. Look up at the URL window at the top of the browser, the address should have 2500w at the end, if not manually enter 2500w and press enter to bring up the largest image.
Test Crop Areas
To see the full size crop image in a new browser tab, 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.
At first glance these images look similar but when you take a closer look the fine details are definitely sharper in the Copal image. Looking at the double lines on each side of the black vertical bar in the center of the image the pink fringing in the Canon image obscures the sharpness of the lines. The lines in the Copal image are much clearer and sharper.
The Copal E18C image is sharper with better chromatic aberration control no doubt.
To see the full size crop image in a new browser tab, 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.
At the edge the Copal has the same advantages over the Canon with better sharpness, and better CA control. The differences between the lenses is actually greater here than in the center crop. The glowing CA issue with the Canon is even worse here at the edge, look at the number 209 and the arrow.
To see the full size crop image in a new browser tab, 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 difference between the lenses in the corners are even larger than the center or edge. The Copal lens is very consistent across the frame but the Canon images show a drop off in image quality from center to the corner. The Copal lens has an image quality advantage over the Canon in the corners. If there is any drop in image quality from the center to the corners with the E18C lens I don’t see it.
The drop off in the corners with the MP-E might have been less noticeable stopped down but there was a noticeable drop off in sharpness at f4 so f3.2 was used for the test. The image used for the corner crop is not the same image as the center or edge. Even though both lenses are well corrected for field curvature I did find slightly sharper results with a different image than the center and edge crop images. All of the images were processed at one time with identical settings.
Test Conclusion
The Copal E18C lens is an easy recommendation especially when you consider the cost. The MP-E has a few advantages over the Copal with a larger magnification range and full frame sensor coverage but at the tested magnification the E18C performed best.
The Copal E18C 40mm 1:4 is highly recommended.
Copal E18C 40mm 1:4 Industrial Lens with rear cell and aperture disk removed
E18C Shooting Notes
The aperture disk in the E18C is installed onto the rear of the front cell with thread locking compound. With the disk removed the lens aperture opens to f2.5 but the image quality also drops.
The Copal lens aperture is preset at f4 but it would be easy to control the lens aperture by changing the size of the aperture disk but at 3.4x the factory f4 setting seemed to be ideal.
Stopping the lens pair down by placing a aperture between the two stacked lenses increased CAs so the factory location looks best at least with the lens pair in this test.
The E18C should be used with a lens hood to prevent flare, I taped on a small tube of flocking material to the end of the lens and this did improve image contrast.
There are two E18C lenses available, the 40mm and the 35mm, both of these are labeled f4 but the 35mm lens is actually faster measuring out at f3.8 but I recommend the 40mm E18C. The 35mm E18C seems to be more prone to chromatic aberrations in the limited testing I have done so far.
Where to Buy The E18C Lens
The 40mm and 35mm E18C lenses are available from an industrial surplus seller on Ebay called ABC-Electronics, you can use the links below or just use the search terms Copal E18C lens. The listings indicate more than 10 units available so they should be around for a little while. My experiences with ABC-Electronics haver been very positive so far, they have been very responsive and helpful.
40mm E18C link:
https://www.ebay.com/itm/Enlarging-Lens-Copal-40mm-E18C-1-4/112949949071?
35mm E18C link:
https://www.ebay.com/itm/Enlarging-Lens-Copal-35mm-E18C-1-4/143039569838?
Seller Link:
https://www.ebay.com/str/ABC-ELECTRONICS-2?