35mm Lens Factors for Large Format Camera Lenses?

analog65 · Aug 3, 2016

Anyone have the lens factors for figuring lens equivalents of 5x7 and 11x14 lenses for 35mm?

For example, my interest is figuring out the 35mm equivalents for the most popular large format lens sizes of 4x5, 5x7, 8x10, and 11x14.

I believe that the lens factor is .30 for 4x5 and .15 for 8x10.

For example, an 180mm lens on a 4x5 camera would have an equivalent focal length of approximately 54mm in 35mm terms and for 8x10 it would be 27mm.

I can't seem to find the lens factors for 5x7 and 11x14. Any help would be appreciated.

Thanks

Ian Grant · Aug 3, 2016

It;s generally assumed that a 150mm 5x4 lens is equivalent to a 50mm lens on a 35mm camera , and for 10x8 it's a 300mm (12") lens. It's roughly a 210mm lens for a 7x5 and a 420 on 14x11.

However as the formats aren't the same proportions it's very approximate, really justa rule of thumb.

Ian

analog65 · Aug 3, 2016

Thanks Ian, I appreciate the info. And, yes, I agree, these are approximate values.

Ian Grant said:
It;s generally assumed that a 150mm 5x4 lens is equivalent to a 50mm lens on a 35mm camera , and for 10x8 it's a 300mm (12") lens. It's roughly a 210mm lens for a 7x5 and a 420 on 14x11.

However as the formats aren't the same proportions it's very approximate, really justa rule of thumb.

Ian

Old-N-Feeble · Aug 3, 2016

Do you use the entire 135 frame or crop to 1:1.25 (8x10) format? Do you print your large format negs full frame or crop them?

If you crop 135 format to 1:1.25 ratio then a 'normal' lens is 38mm... the square root of (24^2 + 30^2).

If you print 135 format full frame then a 'normal' lens is 43mm but it 'looks' a bit wider than 'normal' compared to a 150mm lens on 4x5 film because of the longer format. Taking that to the extreme, consider the Hasselblad Xpan format which is 24x65mm so a 'normal' 69mm lens, as determined using the typical formula, looks quite wide. So the commonly used formula to determine 'normal' focal length on square (or short rectangular) formats doesn't quite work the same with very wide formats. I know you didn't ask about wide formats. The point is 'normal' for 1:1.5 ratio formats, as determined by the common formula, will have a slightly different-looking perspective when applied to formats with 1:1.25 ratio.

DREW WILEY · Aug 3, 2016

The "normal" perspective for any given format is determined by the diagonal of the film. Then you just assign whatever percentage of that you seek.
But working with a view camera generally alters that hypothetical rule because you also have to be aware of the image circle of any given lens relative to the movements view cameras offer, and relative to depth of field considerations related to subject. I'd start with a single realistic lens just
to get accustomed to management of a view camera before deciding about similarity to 35mm perspectives. It's a very different game.

Old-N-Feeble · Aug 3, 2016

What are considered normal lenses are usually rounded up or down a small amount. 50mm for 135 is significantly longer than the true 43mm focal length and much longer than 38mm if you crop the long end to fit 8x10 prints. Printing full-bleed vs. cropping a tiny bit can make a very slight difference too.

On average the following are about as close as you'll get to normal focal length (give or take a few mm)...
135 = 43mm (38mm if cropped)
4x5 = 150mm
5x7 = 210mm (190mm if cropped to 1:1.25 ratio)
8x10 = 315mm
11x14 = 440mm

So it's close enough to use the following factors (if you crop 135 and 5x7 film to 1:1.25 ratio).

135 vs. 4x5 = .25
135 vs. 5x7 = .20 (if 5x7 is cropped to 1:1.25 ratio)
135 vs. 8x10 = .12
135 vs. 11x14 = .086

wiltw · Aug 3, 2016

I use the AOV seen vertically on the frame, since aspect ratio can be considerably different: 1:1 (6x6), 1.25:1 (645 or 4x5), 1.5:1 (135)

Compare FL to the vertical size of frame, so for comparable AOV:

56mm (6x6) = 43mm (645) = 93mm (4x5) = 24mm (135) ... 'superwide' (1* frame height)
110mm (6x6) = 85mm (645) = 180mm (4x5) = 50mm (135) ... 'normal' (2* frame height)
220mm (6x6) = 170mm (645) = 360mm (4x5) = 100mm (135) ... 'portraiture' (4* frame height)

Remember that ALL formats are 1.25:1 when printed on an 8" x 10" piece of enlarging paper and framed!

Old-N-Feeble · Aug 3, 2016

I too use a different formula than the square root of (H^2 + W^2) but I dare not mention it for fear of starting a S-storm.

EDIT: Okay, I'll state my formula anyway and take the hits. I just multiply the long side of the format by 1.3. So if I shot 135 and cropped it to 24x30mm then my normal lens would be 39mm, full frame 135 is 47mm, for 4x5 it would be 156mm, for 11x14 it would be 448mm and for Hasselblad Xpan it would be 85mm. As you can see, this formula 'corrects' a small amount for wider formats. It's not precise but it's closer than the usual formula (in MY opinion). My formula is simpler too.

analog65 · Aug 3, 2016

thanks everyone for such good input!!! I really appreciate it.

Alan Gales · Aug 3, 2016

I'll throw another wrench into your can of worms.

I find that I favor lenses closer to a normal focal length with my 8x10 camera then I did with my 35mm camera. With my 35mm camera I favored my 25mm and 100mm. With my 8x10 I favor my 14" or 358mm. I don't know why but I do.

grahamp · Aug 3, 2016

You start to see this with 5x4, but it seems to get more apparent as one goes to larger negatives. 35mm experience suggests twice the negative diagonal for a portrait lens (90-100mm). On 5x4 that would be close to 300mm, but 210mm seems to work fine.

DREW WILEY · Aug 3, 2016

My idea of "normal" for 4x5 used to be 210, then it went to 250. Why? My older brother was in a pro photog school and they always told the students
to buy a 210 for general usage and a 90 for architecture. That's back when affordable lenses with enough image circle for teaching and portraiture implied something distinctly longer than the mathematical "normal" 150. So I took that advice for my own first view camera (a Sinar 4x5) and used
a 210 exclusively for about a decade. When that lens (a Symmar S) eventually started showing wear and tear, the German Mark was high but the
Yen low, so I sold it and bought a 250 Fuji, which I seem adapted my own way of seeing to. And to me, 180 seems "wide" by comparison (though I
do own true wide-angle lenses for architectural interiors, caves, etc). But for 8x10 I tend to scale that back a bit. Maybe my arms aren't as long as
an orangutan for fiddling around with extremely long bellows, or I just like the way shorter lenses "feel" in that format; but my favorite focal lengths
or pair of "normals" for 8x10 happen to be 360 and 450. With 4x5, I could do most things I want with a 200 and 300 combination, though if I happen
to have the 450 along, which I often do, it's likely to get used too. I gravitate more to long focal lengths and narrow persepctives rather than wide-angle views. I let my eyes dictate all this rather than the math.

Alan Gales · Aug 3, 2016

DREW WILEY said:
I let my eyes dictate all this rather than the math.

+1

There is a lot of math, chemistry, science, etcetera involved in photography but the 3 most important things are your two eyes and your brain.

wiltw · Aug 3, 2016

Let's look at the issue in this fashion...you are accustomed to shooting a portrait of an individual with 135 format using 100mm lens, with camera positioned at 9' from the subject. That frames an area which is 37.5" tall x 25" wide, which you enlarge to print 10" x 8" and fit in a standard frame.

135: 24mm short dimension of frame captures 25" with 100mm at 9' shooting distance;
100mm FL = short dimension * 4.2
645: 43mm short dimension of frame captures 25" with 180mm at 9' shooting distance;
180mm FL = short dimension * 4.2
4x5: 93mm short dimension of frame captures 24-25" with 390mm at 9' shooting distance;
390mm FL = short dimension * 4.2

...SAME width area fitting within the 8" dimension of the print with all three formats!

Let's face facts: The 135 format SLR had been offered by manufactures with lens FL from 50mm to 58mm, all as 'normal'. So to use that starting definition with which to define other lens FL choices is NOT using anything but an arbitrary starting point.

35mm Lens Factors for Large Format Camera Lenses?

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