What distance needed to enlarge to 30" x 40" with 135mm or 150mm lens for 4x5?

[David Wolf]

Looking for some info to help me design an adjustable enlarging table, please. Would anyone know ~ or have a formula for ~ what distance is needed between the negative stage and easel to make prints measuring 24" x 30" and 30" x 40" with a 135mm and 150mm lens for 4x5 format?

Also, anyone have experience regarding comparative sharpness/fall-off at these print sizes for Schneider's Componon S lenses, and their Rodagon counterparts? Haven't found specific magnification info for the Schneiders; Rodagon lists 2x min, 6x opt and 10max magnification. I'm unpracticed reading image fall-off charts, so any first-hand user experience would be helpful ; )

Many thanks in advance to all!

D

[Bob Salomon]

If you have limited space and want large prints the 120 Rodagon WA is a spectacular performer and will make a 20% larger print as the 135mm at the same head height.

[Drew Wiley]

In terms of falloff risk, I'd far rather use a lens of longer than normal focal length like the excellent 180 Rodagon, provided you design your setup with enough height. But if you don't have enough vertical distance, follow Bob's advice. It all depends on the specifics. What enlarger chassis, head, and mixing box options are you contemplating? Ceiling height?

[Jerry Bodine]

Some time ago I found the formula that explains all this in Way Beyond Monochrome Ed.2, so I created an Excel file that allowed me to calculate and plot the curves that result. I’ll attach an image of the plotted curves for the 135 and 150 focal lengths. The 24x30 would be a mag of 6; the 30x40 would be mag of 8 (40/5).

Regarding light falloff into the corners of an image, perhaps you’ve heard of the cosine fourth law; it’s worth looking into. It will explain why a longer focal length lens will have less falloff than a shorter one, given the same magnification.

[Emmanuel BIGLER]

Hi!

The requested distances are very easy to compute.

Knowing the focal length f, 120, 135 or 150 mm, and the enlarging magnification M, 6 or 8, the following formulae apply

lens to image distance = LID = f(1+M)
lens to film distance = LFD = f(1+ (1/M))

hence we eventually find
f = 120mm M=6 ; LID = 840mm M=8 ; LID = 1080mm
f = 120mm M=6 ; LFD = 140mm M=8 ; LFD = 135mm

f = 135mm M=6 ; LID = 945mm M=8 ; LID = 1215mm
f = 135mm M=6 ; LFD = 158mm M=8 ; LFD = 152mm

f = 150mm M=6 ; LID = 1050mm M=8 ; LID = 1350mm
f = 150mm M=6 ; LFD = 175mm M=8 ; LFD = 169mm

[Tin Can]

I draw with pencil and paper to make it visual

OP may easier think of the 2 cones of light

[ic-racer]

Also, anyone have experience regarding comparative sharpness/fall-off at these print sizes for Schneider's Componon S lenses, and their Rodagon counterparts?

D

The lenses all use the same optical physics. You are barking up the wrong tree here. The light falloff problem will be related to your enlarger's light source. This can be anything from a hot spot to 100% even coverage. You don't mention your enlarger's light source, so we can only guess the problems you might have. In general a mixing box one size larger will give the least headaches in terms of coverage at the corners.
If using condensers, you need the exact combination of condensers to match your lens focal length and the magnification. Your lamp has to be the correct diameter or larger to make it all work. This might be impossible due to shortage of appropriate lamps.

[Bernice Loui]

More than just the enlarge head distance to base board required to achieve the print size needed, lens focal length, enlarge alignment from head to base board, inherent light fall off of the lighting system_lens_ and all. Comes the need for enlarger light source power. Keep in mind the amount of light needed to project an enlarged image from film on to the base board of this size to keep the print paper exposure times reasonable.

Powerful light sources demands proper film cooling and means of keeping the film to be projected flat for as long as the film is being worked on in the enlarger.

This is where a GOOD enlarger, light system, lens and all makes a very real difference in print making.


Bernice

[Drew Wiley]

You always want a surplus of wiggle room if possible. And there are no hard parameters formula-wise. What constitutes a nominal 30X40 inch prints size is affected by how much you might crop the original negative as well as what size margins you desire around the image portion of the print paper.

I just checked my own tip sheet out in the lab, but can't give a hard answer. When I did frequently make 30X40's from 4x5 film, I was using a horizontal enlarger on sheave rails. Now, if color at least, I would more likely being using either 8x10 film or an 8x10 enlarged internegative from 4X5. If I were using the vertical Durst L184 with its full oversize 12X12 inch mixing box, I can actually get a fully even field of illumination with a 150 Apo Rodagon N stopped down to f/8, but not with the 5X7 enlargers, where I'd either need a convex diffuser or longer lens to achieve that. A 180 lens would probably need over 6 feet between the negative stage and baseboard - almost on the floor. I've never even printed 4X5 in my really big vertical 8x10 additive color enlarger; but it will easily handle 30X40 prints from 8x10 film with a 360 lens, with the vac easel at comfortable waist height. I obviously have a high ceiling there. The enlarger itself is nearly 14ft tall.

[Tin Can]

I suggest you follow this guy, he shows everything including distances

https://www.timlaytonfineart.com/blog

I also have an XL wall mounted and could do what you want, but I don't want to