Is it a linear progression between 90mm and 150mm?

[AdamD]

Hi all,

I'm an now a proud owner of a 90mm and 150mm lens (4x5 format). If I want a lens right in the middle of these two lenses would that simply be a 120mm?

Is it a linear progression between lenses?

I kinda don't think it is....would the "visual" middle be closer to something like 105mm?

Thank?

[Dan Fromm]

Learn to do the calculations.

But since ..., On 4x5 a 90 mm lens covers 80 degrees. A 150 covers 53 degrees. The average is 66.5 degrees. A 114 mm lens, as was fitted to some relatively high end Polaroid folding cameras, covers 66.5 degrees on 4x5.

[AdamD]

Ok so you are "doing the math" based on field of view. And based on that would correspond to the 114mm lens. Im not even sure that exists, so a 110mm or 115mm should do the trick.

[Alan Klein]

Here's a handy calculator to figure out the various angles of views for different lenses on different formats.

https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#{%22c%22:[{%22f%22:19,%22av%22:%2216%22,%22fl%22:150,%22d%22:30480,%22cm%22:%220%22}],%22m%22:0}

[Dan Fromm]

Ok so you are "doing the math" based on field of view. And based on that would correspond to the 114mm lens. Im not even sure that exists ...

I pointed you at one, you !@#$%.

[AdamD]

This is awesome!! Thank you!

[Michael R]

The next shorter lens I have after 150 is 110. I wanted the equivalent of a 35mm lens on 35mm, which is a focal length I use often. 110 is a little short, but good enough. There wasn’t really anything longer.

[Jody_S]

The difference between 114mm and 120mm is negligible. There's a reason the big lens manufacturers all made 90mm, 120mm, and 150mm lenses, this is what photographers wanted. And your 120mm lens might actually be 116mm or whatever, if you look up the specs in the lens tables.

[Lachlan 717]

I pointed you at one, you !@#$%.

(Re)incarnation of Stone III AND/or Cosmic Explorer?

[neil poulsen]

For my progressions, I've always picked a percentage, and then made each successive focal length that percent more than the last focal length. So, increasing the focal length by 33% each time would give me a progression of about . . .

90, 120, 160, 213, 284, 379.

So, this progression might match up with the following lenses . . .

90mm, 120mm, 150mm, 210mm, 300mm, and 360mm. Or, there 'bouts.

But in terms of field of view, I'm not sure this makes sense. So, I need to think about this some more???

Will be back a little later.

Well, I'm back, and I thought about it.

For me, the multiplicative approach (above) works best. Every time I've increased the focal length by 1/3rd, I've "shaved" off close to 12.5% on each side of what I see on the ground glass. As a progression, I think that it makes sense to add or subtract a constant percentage of what one sees on the ground glass, each time one steps up, or steps down the progression of lenses. This is what a multiplicative progression accomplishes.

In fact, I like staying between about 25% and 33% in my progressions. That makes for more lenses; but, this enables me to "fill" the negative with a composition, once I've established a camera position. Thereby, one retains the advantage of a large format negative.