Resolving power of enlarging lenses

[MartyNL]

So I was talking to this bloke the other day and he was saying that he always prints with enlarging lenses designed for the next format up from the format he is printing.

It's well known that sharpness decreases from the centre of a lense towards the edges. So the theory being using a longer focal length lense than the format requires means using more of the centre and giving "visibly sharper prints" especially at the edges.

So if your enlarger can handle it, why not do it?

His argument holds water and since some of you guys have been around the block a few times and back again regarding darkroom issues I hasten to add!

Has anyone had this discussion or got any experience or views on this?

[Dave miller]

I suggest that,if you haven't already done so, you test this theory.

I would expect a quality lens closed down by a stop or two to be sufficiently sharp across it's field so as not to exhibit unsharpness towards the edges of a print made with it.
Having said that I do often print with a longer than "standard" lens simple to get the enlarger head out of my way when making small prints.

[Mike O'Pray]

I'll have to give this a try, Marty. In 5x7 prints with a 50mm lens for 35mm negs, I haven't noticed any lack of edge sharpness but as you say the theory hold up. Another possible benefit in small prints is that the 80mm allows you to set the lens height higher. With the 50mm the lens is getting very close to the easel with difficulties for using the focus finder.

Mike

[Neil Smith]

I have heard this theory before and have wondered if it is true myself, I often print this way, but to get the enlarger head out of the way, which I prefer when having to dodge and burn.


Neil

[Rob Archer]

I usually print 35mm negs to 10x8 ins and 6x4.5 negs to 12x9.5 ins and use a Minolta EL 80mm for both. I only use a 50mm (Nikon EL) if I want bigger prints from 35mm. stopped down to f8 of f11 is excellent, and I haven't seen any falloff in sharpness at the edges even at 12x16 ins.

Rob

[marty]

I've once printed from 35mm negs with an 80mm lens and honestly I didn't see an improvement in overall sharpness. The only difference was, obviously, the longer exposure time due to the more head height required. I don't think it's a myth, though. I recall reading AA used to do so all the time. Probably the habit came from the times when the quality of enlarging lenses wasn't so good. Old habits are just hard to die. As of today I don't think it's a useful practice anymore (doesn't do any harm either), unless there are other reasons to do so (enlarging only a part of the neg, or getting longer exp times for example).

Cheers, M.

[Trevor Crone]

I've used enlarger lenses longer then necessary for the format because they give more even illumination over the projected area.

[Dave miller]

Originally Posted by Trevor Crone

I've used enlarger lenses longer then necessary for the format because they give more even illumination over the projected area.

Isn’t that more a function of enlarger design than lens performance.

[Trevor Crone]

Originally Posted by Dave

Isn’t that more a function of enlarger design than lens performance.

All things being equal - yes

[Xpres]

I think the argument goes that it's true up to a point. That point being that as the FL of the lens increases it doesn't have to resolve so much due to the larger format they're used with, so they don't make them as high resolving as those for smaller formats. So although you're using the best bit of the larger lens it's still not as good as the smaller.
The only benefit might be sharpness to the corners, but then only if you're using a slightly longer lens than 'normal' and if your 'normal' wasn't much good in the first place.