Reason for needing different lenses for different formats

[bence8810]

Hello all,

A potentially silly question here but I just can't wrap my head around this.

What is the reason we need different focal lengths for different formats when enlarging 135 / 6x6 / 6x7 / 6x9?

I currently print from 135 and 6x6 and use a 50mm and 75mm lens for this.
50mm for 135 and 75mm for 6x6.

My question is - why can't we just use a 50mm for all formats and then potentially get away with a smaller enlarger?
I am sure there's a good reason for this which is what I am trying to understand.

2nd question - let's say I'll be printing only 6x6 and 135 in the future. Do I need to always swap back to the 50 for printing 135 or I can just use my 75mm for both 135 and 6x6?
And if I in the future print 6x9 and use a 105mm lens - can I then use that for all formats including 135?

Thanks,
Ben

 

[Jan Pedersen]

It works a little the same way as it does on a camera.
A 50mm enlarging lens would not cover medium format film unless a special lens with large image circle. You can however use a 105 for all formats up till 6x7, I am not sure a 105 will cover a 6x9 negative.
The disadvantage using a long focal length for 35mm is the extended exposure time because of the distance from lens to paper. As you go up in enlarger lens size the distance from lens to paper increase. If you can live with longer exposure time there is no reason to use a 50mm for 35mm film if the 105mm lens resolves the same as your 50mm.
Hope that helps.

 

[Doug]

Ben, it's a matter of angle of view, and the "coverage" that the lens is capable of. For instance, the 50mm enlarging lens cannot "cover" the 6x6 format, as it can see only a ~40mm or so circle diameter, cutting off the edges and corners.

But if it could see the whole 6x6 frame size, then it would be a pretty wide-angle lens, which would require it to be down close to the paper for smaller prints, while on the other hand raising the head to a more normal level would result in quite large prints.

As one example, I wanted to make some 11x14 prints from half-frame 35, negatives 18x24mm, but I couldn't raise the enlarger head high enough for a 50mm lens to do that with the small neg. So I placed my 35mm Summicron on top of a spare lensboard, and that allowed me to comfortably make the larger prints. I would have used a 35mm or so enlarging lens if I'd had one... but it worked. At the same time I use an 80mm Nikkor for 6x7, which it can cover well, and the slightly short focal length for that format lets me make bigger prints at the same head elevation.

Similarly if you had a 105mm enlarging lens, it could make only small prints from 35mm negs, and with the head very high. At the same time, your 50mm enlarging lens would make a decent print from 6x9 negs, but only from the center portion of the neg. The 50mm doesn't have enough coverage to see the whole neg, and if it did, the lens would be inconveniently low to the paper easel.

 

[bence8810]

Hello both,

Thank you for these points - I now understand.
So I guess if I stick the 75mm I have on - I can use that for both 6x6 and 135. I actually was quite frustrated with the short enlarging times I get with the 50mm so using the 75mm with an elevated head placement should help me in that department.

Again - thanks a lot!
Ben

 

[Dwig]

...

My question is - why can't we just use a 50mm for all formats and then potentially get away with a smaller enlarger?...

In theory you could, but there are nor 50mm enlarging lenses made that will cover a 6x6 negative. Making such a lens, and the matching condensers, would be extremely challenging. You need a lens that will produce sharp images center to edge, have negligible rectilinear distortion, and have very even illumination across the whole field. The matching condensers would also be a challenge as they much be large enough to cover the 6x6 image area while also having a short enough focal length to focus an image of the lamp's filament at the plane of the enlarging lens.

You can get away with using the longer lenses made for 6x6 with 35mm negative, but you need to leave the condensers set for 6x6 and suffer the associated light loss. You also will be limited in how large you can print without resorting to wall or floor projection.

For years I used a 150mm lens (made for 4x5 negs) to print 6x6, 6x7, & 6x9. It worked well, but I was using a monster Beseler 4x5 enlarger which was wall mounted an configured for easy floor and lower baseboard projection allowing easy configuration when making larger prints.

 

[oftheherd]

It works a little the same way as it does on a camera.
A 50mm enlarging lens would not cover medium format film unless a special lens with large image circle. You can however use a 105 for all formats up till 6x7, I am not sure a 105 will cover a 6x9 negative.
The disadvantage using a long focal length for 35mm is the extended exposure time because of the distance from lens to paper. As you go up in enlarger lens size the distance from lens to paper increase. If you can live with longer exposure time there is no reason to use a 50mm for 35mm film if the 105mm lens resolves the same as your 50mm.
Hope that helps.

Normally you want an enlarging lens of about the same focal length as the normal lens for the film format you are using. Since the normal for 6x9 is considered to be about 105mm, it would do well for 6x9. Generally it goes like this:

50mm = 35mm film
75/80mm = 6x6 film (and usually 645)
105mm = 6x9 film
135mm = 9x12 film
150mm = 4x5 film
300mm = 8x10 film

 

[Ronald M]

Times do not increase if a longer lens is used, only distance from negative to print.

You do not want to use a wide angle lens on condenser enlarger.

If your lens is too short, the edges of the neg will be cut off. Too long, see first sentence.

 

[Dwig]

Times do not increase if a longer lens is used, only distance from negative to print. .../quote]

With condenser enlargers, a very well adjusted condenser set will often produce more intense illumination when adjusted for a shorter lens, as would commonly be used for smaller formats. When using a longer than normal lens, the condensers must be adjusted for that longer lens and will be illuminating a larger area at the negative stage and will be somewhat less intense.

 

[bence8810]

Times do not increase if a longer lens is used, only distance from negative to print.

... which increases the time required for an enlargement to be made - no?
If the negative is closer to the paper - so is the lamp source and therefore less time is needed. Am I wrong with this assumption?

All in all I am more confused than I was before asking the question.
I don't have separate sets of condensers - I just have the one that came with my enlarger (Lucky 90M-D)

It came with 2 lenses - the 50mm and the 75mm and also two negative carriers - one for 135 and one for 6x9 which I use for 6x6. I also have two lens boards but not sure if I need to use them both. They are the same exact thing. I assume it would help mounting the lens easier as I wouldn't have to unscrew them all the time? Not sure.

I was just hoping to keep the 75mm on all the time but if I am losing out on quality when using it with 135, I'll better be swapping all the time.

Thanks,
Ben