[Copal #0] The Rodenstock 75mm f/4 APO-Rodagon D lens is sold as an enlarger lens @ B&H, but it is NOT an enlarger lens.
The Rodenstock 75mm f/4 APO-Rodagon D is a lens for reproduction/duplication with a scale of ONLY 0,8:1,2.!!
So useless as an enlarger lens to make analogue photo prints.
I almost bought the lens, but spoke with a German company that explained me that the D lens is for Duplicating, not for darkroom use.
If you would use the lens as an enlarger lens its for prints with enlargement factor-scale range 0,8-1,2 only,
That means: negative size 6x4,5cm = 60x45mm = prints between 48mm x 36mm and 72mm x 54mm !!!
Millimeter, not centimeter !

[f/4] Since I owned and enjoyed the quality of Rodenstock and its APO-Rodagon-N 105 mm lens for my medium format film for many years, opting for the second lens -- the APO-Rodagon-N 50 mm was a sure and easy way. I need an ultimate quality of the glass when I print 35-mm negatives that require a perspective correction. To wit: I often tilt the head of my Saunders LPL enlarger to achieve the parallel lines of architectural structures. With this lens I don't need to compromise on quality. The results are astounding!

[5.1 x 5 x 5"] I had used the regular Rodagon 80mm for some time, making color and B&W enlargements up to 24x42 and was quite happy. Then I was loaned the APO by the Rodenstock reps. Using a DeVere 4x5 single bulb color head, from 645 negatives enlarged bigger than 16x20, there was a marked increase in sharpness, contrast(at least 1/2 a grade on B&W) and the contrast and corner sharpness as well as even-ness of illumination across the image field was surprising. I've been a professional lab technician/photographer(mostly industrial/commercial) since 1973. I've never used a better quality lens, for the finished results. It IS breathtakingly exspensive. It will cover with no fall-off at f8 the Fuji 6X8 cm format. If you have older generation enlarger lenses, even very good lenses, you are short-changing yourself without the APO series lenses. No new HDTV for me this year...three new APO Rodagon N's for me(50, 80, 105mm the 150 will have to wait a year). I have had no qualms about using this lens at F5.6 on 20x24's. It's grain-sharp into the corners. I really like the feature of using continuously variable f-stops with an on-easle densitomiter. F7.3 at 12 seconds maybe perfect. BTW: by a Minolta Flash Meter III, the F-stops are with-in .3 stops of perfect from wide-open to f22. I know lots of you silver B&W guys are using old glass because you have it and it looks OK. Try an APO, and you'll spend twice as much time in the darkroom, making far more much better prints. Yes, I am hyped. Ricky Earp

[5.1 x 5 x 5"] The 80mm APO-Rodagon N is one of the most perfect lens formulas I have ever used. The other is the Zeiss 100mm Makro-Planar. I not only enlarge with this lens (less now since I moved to carbon transfer printing, which is a contact printing process), but I mount it on a Nikkor PB-6 Bellows with an adapter and record images with a Sony a7RII on the other end of the apparatus. The results are astounding for sharpness, flatness of field and freedom from aberrations. The PB-6 Bellows with the attendant adapter to mount the a7RII will not focus to infinity with this lens but that is not the magnification ratio at which it is optimized in any case.

[Copal #0] I have had this lens for a short period of time mounted on a Linhof Super Technika V with a Leaf Aptus II 5 digital back. When properly adjusted on a Technika with the right cam, you can focus this lens exactly through the range finder on the Technika. It's image quality and colour are without peer. Outstanding. No Distortion. Complete control of depth of field. Optimum aperture at F4 - f 11. Very quite. No fringing, super sharp and colour that matches Slide film. The image quality from this lens is that good that when you look at the fashion images and the pictures in books and magazines, you say to yourself, I can do better than that. The Pros of this world should wake up to the quality these lenses produce. Forget the Leica S2 and the M9 (both I have used). This combination is large format near transparency quality on digital.

[f/22] This lens replaced a Nikon El Nikkor 50 2.8 The first prints I made from it was clearly superior in terms of gradation and sharpness to the Nikon. It is a real gem of a lens, instilling confidence when I set out to make a print from a good 35mm negative. All 4 of my enlarger lenses are now German made glass. This Rodenstock has mechanical extras such as click/smooth aperture stop adjustments and aperature pre-set.

[1.04 lb] I recently was able to compare this with a Schneider 45mm APO that I have. Admittedly, at all magnifications, I simply couldn't tell the results apart. Both had great sharpness, almost identical contrast, lack of vignetting and even sharpness across the image. I prefer and use the Rodagon as it's a bit brighter for composition but could happily use either. I'm leaving this review in case someone is choosing between the two. I'd use a coin flip to decide! Remember that these tend to be sharpest relatively wide open (I use 4.0-5.6 most) so you need to have your equipment properly aligned as there's little depth of field to add forgiveness for alignment issues. Glass carriers help to extract what this lens can do, too.