210mm Rodagon-G - optimal stop for a large mural print

[LF_rookie_to_be]

Within the next few months I plan on making a LARGE print (52x70") from a 4x5 color negative using a Rodagon-G 210mm f5.6 lens. I have an AN glass carrier and a 200W bulb in a dichroic head. Any possible reflections from walls, tables etc. can be minimized with a black matt cloth which I have good supply of. My question is, what is the optimal aperture for this feat on this particular lens?

Also, any other ruminations/suggestions about alignment problems/solutions are more than welcome!

Thanks.
LF_rtb

[Jim Jones]

What is the optimum aperture of your lens in your enlarger? With such a big enlargement it should be easy to see on the easel. Other similar lenses may have different optimum apertures.

While checking for the optimum aperture you can also check for alignment problems. I usually do this by focusing slightly above the easel and checking to see if the image is focused at this distance over its entire area. On some enlargers it is easier to shim the negative carrier or easel to align everything than to make more permanent adjustments.

[BetterSense]

I have a feeling with this big of a print you might as well use the lens wide open. I don't think you will have much choice.

[frotog]

With a 200w head, glass and a 210 (kind of long for 4x5 so more fall-off) you'll have exposures of at least one minute even with a thin neg. and the G wide open. The G series is plenty sharp wide open... no problem there.

[Bob Salomon]

You would get better results and shorter print times with either the 150 Rodagon G (optimized for a 4x5 rather then the 210 which was made for 5x7) or with the 150mm Apo Rodagon-N since you are only making a 14x print you would be within the optimization range of both of those 150mm lenses.

[ic-racer]

My experience has been that by using just the center of the lens field, you can exceed the magnification specs of a lens, as in this case of using a non-high mag 210mm for 4x5. If your negative and lens are perfectly aligned, I'd think you could use f11 and have 4 sharp corners. This is using a horizontal enlarger, right? Otherwise, you will need a shorter lens and, therefore, should heed the advice in Bob's post.

[Bob Salomon]

My experience has been that by using just the center of the lens field, you can exceed the magnification specs of a lens, as in this case of using a non-high mag 210mm for 4x5. If your negative and lens are perfectly aligned, I'd think you could use f11 and have 4 sharp corners. This is using a horizontal enlarger, right? Otherwise, you will need a shorter lens and, therefore, should heed the advice in Bob's post.

The G series are all mural lenses only for large sizes. 14x is in the middle of their range.

That being so, the modern 150mm lens will outperform a modern 210mm for 4x5. Not to mention the extra column height needed to reach a given magnification with the longer lens which leads to much longer exposure times or the need to use a larger then optimal aperture and the greater chance for vibration effecting the final print due to the increased time and column head height.

With very, very old lenses a longer focal length was frequently needed but not with lenses like the Rodagon G or the Apo Rodagon-N.

[LF_rookie_to_be]

@ frotog

Can you please explain the reason for a 210mm G lens (or any 210mm lens) having more light fall-off for 4x5? Do you mean, compared to 150mm?

@ Bob Salomon

A 150 G is pretty hard to find and an Apo 150 is usually quite expensive - used, let alone NOS/BNIB. This 210 G was $60 and mint, so it will have to do for now.

@ ic-racer

Unfortunately, I won't be using a horizontal enlarger, but a Fujimoto 450M-C with the head rotated 90 degrees.

[Bob Salomon]

@ frotog

Can you please explain the reason for a 210mm G lens (or any 210mm lens) having more light fall-off for 4x5? Do you mean, compared to 150mm?

@ Bob Salomon

A 150 G is pretty hard to find and an Apo 150 is usually quite expensive - used, let alone NOS/BNIB. This 210 G was $60 and mint, so it will have to do for now.

@ ic-racer

Unfortunately, I won't be using a horizontal enlarger, but a Fujimoto 450M-C with the head rotated 90 degrees.

The 150G should not be hard to find with all of the labs going out of business. Being able to buy a lens for $60.00 hardly seems the killer requirement if you are trying to make huge, quality prints. Justifying the lens because you found the wrong lens at a good price shouldn't keep you from looking more. There are so many labs going out of business that these lenses should be around. Just check commercial printing labs that are closing or having clearence sales. The G stopped selling when mural printing went to ink jet so these lenses are not typically used today in the labs.

[LF_rookie_to_be]

150G found, almost new, box and all. Thanks to Mr. Salomon for the advice. Anyone feels the need to share their experiences when it comes to aligning? Does the laser-printed grid or a sharply scratched black negative help?