AstrHori 25mm/f2.8 Macro lens for extreme macros
The AstrHori 25 mm lens is an absolutely special lens, as it can only operate in the range between two and five times magnification of the object being photographed.
Introduction
The lens is completely manual, i.e. without any transmission to the camera. The AstrHori 25 mm 2.8 is available for various full-format cameras, such as Sony connection Fuji X Nikon Z Canon RF and ultimately L – Mount. The lens does not have an infinity setting, as it can only record at a distance of around 40mm from the subject, but the object is magnified in a range of 2:1 to max. 5:1.
The lens costs around €250-270 in Germany and is offered by various retailers. I ordered it directly from Peargear for the L-Mount in a special offer for just under €190.
I also recorded a video about it:
Built quality
The built quality can be described as good, as the lens has a sturdy metal housing. The rotation of the ring for the magnification, rather than the focus ring, is also good. However, I find it a bit tight. This may be because earlier versions of the lens were so easy to move that it adjusted itself depending on the angle. Otherwise, you can manually set the aperture on the front of the lens, between values from 2.8 to a maximum of 16.
Use
As there is no focus ring available here, you can only focus using the distance to the object. With magnification ratios between 2:1 and 5:1, we are moving at an object distance of around 40 mm. Therefore, the use of a focusing slide such as the Novoflex Castel Q is highly recommended.
With this small distance between the front line and the object being photographed, you obviously also have to bring light to it, and smaller video lights or flash units with a diffuser are recommended for this. The light area can be small because the objects are also very small.
Image quality
The image quality is relatively good even with the aperture open, i.e. 2.8, but then increases a good bit at aperture four and 5.6, where it reaches its best performance. And depending on the object, you can already notice from aperture 8.0, sometimes even earlier, especially at a scale of five to one, that diffraction blur occurs here due to the large image scale.
Another problem is that with image scales of two to one and even larger, we are moving in the fraction of a millimeter in terms of the depth of field. This means that even with smaller objects that do not extend too deep, focus stacking or focus bracketing is almost always better, i.e. a large number of shots that are then added together later using the appropriate software.
You can check this very easily using this depth of field calculator, which has a depth of field of less than 1/4 mm at aperture 5.6 and a 2:1.
Here I am showing examples of shots that were taken in the 2:1 or 3:1 range, with a number of shots from 12-68. The shots were then put together using Helicon Focus.
This of course also means that with focus bracketing the feed towards the object can only change by a maximum of this range. Although Novoflex is very precise, this is hardly possible with a Castell Q. However, there is a small additional part called Castell Fine that can be used to make such movements. However, larger image scales with even smaller feeds cannot be achieved with this. For this you might have to resort to the relatively expensive Castell M.
And of course a tripod is a must here, because you will hardly ever get a good shot freehand.
In this range it is also damn difficult to align an object absolutely parallel to the sensor so that things like possible edge blur can be really assessed.
Conclusion
The AstrHori 25 mm 2.8 is a very good lens that allows you to get started with more extreme macro photography at a very fair price. Regardless of the specific lens, however, such shots with image scales of two to one and beyond are a challenge.
What do you think of this lens? I think it’s very good for getting started and for practicing.
ciao tuxoche
