Max Enlargement Size From 6x7 Negative?

[cargosteve]

Hi all! New, here, I've noticed similar versions of this question asked here before, but I wanted to ask for myself with more concrete details including my technique and equipment. I'm curious to know what the maximum enlargement from 6x7 before visible softening becomes an issue. For reference, I've printed 35mm at 5x7 and 8x10 and found the 8x10s very soft compared to the 5x7s. However, the negatives I've tried this with were shot handheld and using a lens that was not particularly sharp. All of the 6x7 negatives I've shot so far (Mamiya RZ67 Pro II) have been on a tripod, mirror locked up, using a shutter release cable, at apertures usually between f/11 and f/45. Ideally, I'd like to make prints up to 20x24 from these negatives, but I don't want the type of softening that I've noticed between 5x7 and 8x10 from handheld 35mm. Subject is landscape, so details are important to me. I've mostly been shooting HP5, Ektar and Pro400h. The enlarger I'm using is a Beseler Dichro 67 head mounted to the rail system from a 23c series model. Enlarger lenses I have for MF are EL-Nikkor 80mm f/5.6 and 105mm f/5.6. I currently don't have an easel large enough for 20x24, but when my darkroom is back up and running I plan on testing on 8x10 paper at the desired enlargement size. In the meantime, I was hoping to get input from this wonderful community! Thank you in advance for your help and input!

[randy_boren1]

You should be just fine at 20x24 with your setup. I would suggest using the 105mm enlarger lens at f/stop 8 or 11 for best sharpness. At that magnification and f/stop you will have some very long exposure times SO, everything must be still, no vibration at all, do not move/walk around, hope that no large trucks rumble by during exposure. 

[rodeo_joe1]

9 hours ago, cargosteve said:

Subject is landscape, so details are important to me.

Then why are you using 400 ISO films? 

When T-max 100 first came out I was previously shooting FP4, and the difference with T or delta-grain films was like moving up a format size.

Anyway. The 645 format easily gives me sharp and practically grainless 12" x 16" prints from 100/125 ISO film. So 20"x24" from 6x7 should be equally good. 

7 hours ago, randy_boren1 said:

At that magnification and f/stop you will have some very long exposure times

There should be no need to stop any decent enlarger lens down to f/11. An El-Nikkor probably peaks in sharpness at f/8 and loses out to diffraction at smaller apertures. The only reason to use a smaller aperture would be to give yourself more time for dodging or burning operations on a tricky neg. 

Modern printing papers are so fast that in many cases the printing time is actually too short at the optimal aperture of the lens. But you're probably in the 'sweet spot' zone with a 10x enlargement - which is all that a 20"x24" print from 6x7cm is. 

Having said that, the advice to minimise any vibration is always good. Especially since you need a minimum column height of about 1.3 metres for a 10x enlargement with a 105mm lens. 

The Beseler Dichro head should be plenty bright enough if fitted with the recommended lamp. 

Edited October 19, 2022 by rodeo_joe1

[laurencecochrane]

46 minutes ago, rodeo_joe1 said:

Then why are you using 400 ISO films? 

I agree but. The Ektar I use is 100.  Is it available as 400 ? NOT KNOW ! Never use 400 I have a tripod.

[cargosteve]

Thank you all for your input!

8 hours ago, rodeo_joe1 said:

Then why are you using 400 ISO films? 

When T-max 100 first came out I was previously shooting FP4, and the difference with T or delta-grain films was like moving up a format size.

Good question, I guess I like the color profile of Pro400h for landscape. As far as HP5 goes, I suppose I like the latitude and find the grain with that specific stock pretty nice for a 400 speed film. I also love the way it pushes and pulls so effortlessly. I'll have to try T-max 100, I can't say I've shot anything on that. Would you say Ilford Delta 100 is pretty comparable to the T-max 100? The Ektar as laurencecochrane mentioned is 100 speed.

 

16 hours ago, randy_boren1 said:

I would suggest using the 105mm enlarger lens

Is there a particular drawback to using the 80mm lens in this situation? As rodeo_joe1 mentions, the enlarger head would need to be way up there for 20x24 prints.

Thanks again.

[jose_angel]

There are many factors to consider when working on the sharpest prints.

Leaving aside the taking and the type of film and the developement (it's not only the size of the grain but also the shape of the developed grain), the main problem I see is on the enlargement process.

All planes (film, lens, paper) must be absolutely parallel, so a perfect fit must be achieved. The Beseler C series are not easy to adjust, so set the enlarger to the desired height and adjust it as carefully as you can (and your adjustment tools permit). As said, stability is crucial.

I would check the optimum working aperture of the lens. Some lenses are sharp but show curvature of field up to some extent, among other factors. I have never used EL Nikons, but have had surprises with other top notch lenses (supposedly very flat field). A 80 vs. 105? Coverage (light fall off) and peripheral sharpness should be checked. It will depend on the lens.

After all this, the print should be as sharp as the system can produce with that film (image). Anyway, sharpness is somewhat subjective. An image may or may not appear sharp depending on the viewer (but this is another topic 😄 ). My advice is that you consider all this without going crazy and start printing. After all, it must be (it really is!) an enjoyable experience.

Edited October 19, 2022 by jose_angel

[conrad_hoffman]

Highly recommend Ctein's Post Exposure, which is now a free download-

https://ctein.com/booksmpl.htm

 

[conrad_hoffman]

Also, are you familiar with the 2-mirror method of enlarger alignment? As the name suggests, you need two mirrors, one of the baseboard of any medium size and one long enough to go in the slot for the neg carrier. You drill a small hole in the upper one. It helps to put a white notebook paper hole reinforcer around the hole so you can see it. You look through the hole from the top, at the mirror on the baseboard. Any out-of-parallel will be seen as a trail of repeating holes. You can do the same for the lens by holding the drilled mirror against the front lip of the lens. This method is incredibly sensitive and you have to be careful not to pursue perfection that the enlarger isn't capable of.

[randy_boren1]

9 hours ago, cargosteve said:

Thank you all for your input!

Good question, I guess I like the color profile of Pro400h for landscape. As far as HP5 goes, I suppose I like the latitude and find the grain with that specific stock pretty nice for a 400 speed film. I also love the way it pushes and pulls so effortlessly. I'll have to try T-max 100, I can't say I've shot anything on that. Would you say Ilford Delta 100 is pretty comparable to the T-max 100? The Ektar as laurencecochrane mentioned is 100 speed.

 

Is there a particular drawback to using the 80mm lens in this situation? As rodeo_joe1 mentions, the enlarger head would need to be way up there for 20x24 prints.

Thanks again.

The 80mm lens is designed for the 6x6 format, while it can be used with little problem for the 6x7 format, it won't be optimum. The 105mm lens is designed for the 6x9 format, you will have better image quality with the 105mm at 20x24 size enlargement. The OP will have to check to see if the 105 will actually enlarge to 20x24 with his version of the enlarger, it should, but it may be close.

[Jochen_S]

f45?!? - Diffraction alert. 

20x24" from 6x7 seems more enlargement than 8x10" from 35mm. 

I wasn't happy with HP5 135 for landscapes. If you love that film, maybe scale up your camera or viewing distance, for those posters you are planning to print.

[cargosteve]

Thank you all for your help! 
 

On 10/19/2022 at 8:59 PM, randy_boren1 said:

The 80mm lens is designed for the 6x6 format, while it can be used with little problem for the 6x7 format, it won't be optimum. The 105mm lens is designed for the 6x9 format, you will have better image quality with the 105mm at 20x24 size enlargement. The OP will have to check to see if the 105 will actually enlarge to 20x24 with his version of the enlarger, it should, but it may be close.

Ok this is good to know. I checked and it seems like I won’t be able to print quite 20x24 with the 105 on my current enlarger.

Thanks conrad_huffman! I was thinking of investing in the versalab laser alignment tool, but maybe I’ll try the mirror trick you mention. Sounds cheaper.

On 10/20/2022 at 5:14 PM, Jochen1664876637 said:

f45?!? - Diffraction alert. 

20x24" from 6x7 seems more enlargement than 8x10" from 35mm. 

I wasn't happy with HP5 135 for landscapes. If you love that film, maybe scale up your camera or viewing distance, for those posters you are planning to print.

I worried initially the images wouldn’t be usable but they seem pretty sharp to me 🤷‍♂️ Yes, I reckon you’re right that it is a greater enlargement factor, I was curious if better technique would be enough to get better results given the specified conditions. I’ve generally been pleased with HP5, but I’m open to others! Again, I’ll have to try other film stocks and compare side by side.

Edited October 22, 2022 by cargosteve

[AJG]

For what it's worth, Nikon claimed the their 80 mm f/5.6 was designed to go to 6x7.  I have never made prints bigger than 16x20 with mine but the sharpness was always good. You could try setting it up for 20x24 on the baseboard and then making 8x10 prints out at the edges and in the center to see if it works for you.  It wouldn't surprise me if you needed to do some edge burning to make the exposure even over the whole image.

[rodeo_joe1]

On 10/19/2022 at 6:04 PM, cargosteve said:

Would you say Ilford Delta 100 is pretty comparable to the T-max 100?

Not really. I bought a 5 pack of Delta 100 rolls and regretted it. The tonality wasn't as good as T-max 100 IMO, although it might be improved upon by tinkering with the EI and development time. But why would I bother when T-max 100 is more satisfactory at box speed and recommended dev time? 

 

On 10/19/2022 at 6:04 PM, cargosteve said:

Is there a particular drawback to using the 80mm lens in this situation?

Yes, an 80mm lens is definitely a bit short for 6x7, and effectively gets 'shorter' (has a narrower coverage angle) at higher magnifications. A 90mm lens would be a better match to 6x7, while 105mm will definitely cover better. But give the 80mm a try if you don't mind stopping it down to f/11 or further. 

 

On 10/21/2022 at 12:14 AM, Jochen1664876637 said:

20x24" from 6x7 seems more enlargement than 8x10" from 35mm.

It's not though.

8.5 x 24mm = 204mm = 8"

9.07 x 56mm = 508mm = 20"

So, OK a 10"x8" from 35mm needs slightly less magnification than a 20" x 24" from 6x7, but practically the difference between 8.5x and just over 9x enlargement isn't worth worrying over.

[Dustin McAmera]

I don't think it's the short dimension of the paper that's limiting, in the 35mm case. That is, if you enlarge 35mm to fill the 8-inch width of an 8x10 sheet, you've gone over the 10-inch length.

The enlargement to fill the 10-inch length is 10x25.4/36 = 7.06

Enlarging 6x7 onto 20x24-inch, it is the short dimension that limits it. The enlargement to fill the 20-inch dimension is 20*25.4/58 = 8.76

So it is a significant difference, I think.

(editing to add:)

It really matters how many mm you let the '6' dimension be. I took 58 because that's what I measured on some of my 2¼x3¼ negatives - as the absolute edges of the exposed frame, but I know it varies in some of my cameras. I only have one that will take 6x7 - I have a 6x7 back for the Century Graphic, but couldn't tell you if I have ever used it.

 

Edited October 23, 2022 by Dustin McAmera

[rodeo_joe1]

Ah, 7 times versus 8 and three quarter times. It really is no big deal of a difference. An extra 25% linear enlargement is like comparing the grain of 125 ISO film with 100 ISO, and only adds 1/2 a stop to the exposure time.

6 hours ago, Dustin McAmera said:

That is, if you enlarge 35mm to fill the 8-inch width of an 8x10 sheet, you've gone over the 10-inch length.

And made Barnack's overlong format more visually appealing. 😉

BTW, can anyone explain what all the new emojis actually stand for? 

Edited October 23, 2022 by rodeo_joe1

[arthur_gottschalk]

Nick Carver made a giant print from 6x7.  You can find it on Youtube.