About '35mm equivalent' focal lengths

[BetterSense]

In 35mm land, assuming that I intend to fill the frame with the subject, I typically use 50-75mm lenses for bust-length portraits, 90-135mm for face-only portraits, and 28-50mm for full-length/environmental portraits. What would the equivalent lengths be for large format, or rather, what do people find themselves using for these tasks?

I would do a simple comparison based on image diagonal, but I know that the magnification changes when you get up close with a large-format camera, so I don't know how much that effects the focal lengths of lenses used.

[Jack Dahlgren]

Magnification changes would be proportional in either format and since the ranges you give are rather large (ranges of +50% to almost +100%) and the format proportions are substantially different, a multiplication by 3 or 4 for 4"x5" would be accurate enough.

[Lachlan 717]

You'll need to let the group know which format you're referring to.

However, if it's for 4x5, have a look at this:

http://spreadsheets.google.com/pub?key=p9VlogmKEIcZHFDoKQluQSA

[BetterSense]

It's for 4x5.

I have a speed graphic with a 127mm lens, which is the only lens that works with my rangefinder. But for the monorail camera I just bought, which will be used for portraits and still-lifes, I think I should use a slightly long lens. And not having any lenses to try for myself, I have to guess what focal length I want. But when I focus even my 127mm lens close, the magnification changes significantly, so that would tend to make me think I don't need as long of a lens as I would otherwise calculate, since the macro regime is so much larger in 4x5. And now I'm confused.

[Lachlan 717]

In (very) general terms, for the portraits, somewhere between 200-240mm is used.

But it's like how long is a piece of string. Some use much longer lenses. Some shorter. Your vision is your vision; only you will know if a lens is "right" for you, and that is after you try it.

Additionally, you'll need to consider what "style" of lens you're after. Do you want a super-sharp portrait where every freckle, scar and blemish is obvious? Do you want a softer, dreamy image? Do you want weird, swirling backgrounds as delivered by Petzval-designs?

Perhaps direct us to images that you like. In that way, the super smart and super able folks here might be able to shortlist some options for you to research/consider further.

[BetterSense]

Do you want a super-sharp portrait where every freckle, scar and blemish is obvious?
Basically. My theory is that images are more easily softened than sharpened, and the lens won't always be used for portraits. It might need to be used for landscape/still life as well. Right now I'm trying to decide on a length. I have used a 210mm process lens before and I think it's a pretty good length for bust-length portraits.

[Lachlan 717]

There is a thread running at the moment about "Sharpest 210mm); might be worth having a look.

I like the Schneider APO-Symmar 210mm (non-L) as it is an update on the Symmar-S and cheaper than the APO-Symmar L. And, like any of these modern lenses, it is super sharp. Mind you, I doubt that I could tell the APO lenses from the Symmar-S....

I also really like the Fuji 210mm. For colour work, I like the slightly warm tone that Fujinon glass seems to give. But that is significantly subjective!!

There is no doubt in my mind that a Nikkor or a Rodenstock will also be a great lens at this FL. It is/was a very popular length, so the major companies made sure that they got it right.

[Matus Kalisky]

I would do a simple comparison based on image diagonal, but I know that the magnification changes when you get up close with a large-format camera, so I don't know how much that effects the focal lengths of lenses used.

I guess that with this you mean that the large the format the more one moves towards macro (at least with tight head shots) what makes the effective length longer. You are in principal correct, but give that even a tight head shot with 4x5 is around 1:3 your effective focal length does not change too much. I guess this is quite different with 8x10 where you are getting close to 1:1.

[ic-racer]

I know that the magnification changes when you get up close with a large-format camera, so I don't know how much that effects the focal lengths of lenses used.
Thats a good question that no one ever asks. Perhaps someone has already done a spread sheet for that. Since I shoot mostly outdoors, my spreadsheet of focal lengths does not incorporate angle of view changes with near distance focusing.

[rdenney]

Basically. My theory is that images are more easily softened than sharpened, and the lens won't always be used for portraits. It might need to be used for landscape/still life as well. Right now I'm trying to decide on a length. I have used a 210mm process lens before and I think it's a pretty good length for bust-length portraits.

It isn't just making an image soft, it's making a pleasing soft rendering, which is a different thing and quite difficult to duplicate in Photoshop depending on which rendering you prefer.

One option is a lens that is a bit soft wide open but that sharpens up as you stop down, making the lens versatile for portraits and landscapes. I'm sure there are many examples, but one common possibility is to get a tessar design instead of a plasmat. Tessars don't have the coverage of plasmats in large-format use, but at this focal length it doesn't really matter. (All the common modern lenses at this focal length, including Symmars and Sironars, are plasmat designs.)

As an example, Ilex made their Paragon lens in 8-1/2" (215mm) with a maximum aperture of f/4.5. These are not that uncommon and they are pretty cheap when they appear. At f/4.5, they are effective portrait lenses for an old-fashioned large-format look, but by f/8 they are plenty sharp for landscapes. They were made in the 50's and 60's and are coated. The only downside (which isn't really) is that they come in an Ilex No. 4 shutter, with shutter speeds that have become somewhat approximate. But you can test it to note variations from the markings, and they are reliable shutters once brought up to a state of good repair.

Here's another example: Calumet marketed a 240mm lens back in the 70's for a brief while: The Caltar Type Y 240/6.8. It is a Rodenstock Ysar design, which is also a tessar. It's not as fast as the Paragon, but the smaller maximum aperture means that it fits in a No. 1 shutter (mine is in a Copal), while plasmats longer than 210 usually require a No. 3.

On the subject of equivalent focal lengths, a useful mental formula is to express focal length as a multiple of the frame diagonal, which is the customary definition of a "normal" lens. Thus, a 210 used for 4x5 is 1.4 times the normal, which is similar to 60mm in the 35mm format. This is approximate in that it doesn't consider the effect of the shape (35mm is more rectangular than 4x5, of course), but your ranges are much broader than any resulting errors anyway. If you prefer an 85 in small format for portraits, that's about twice normal, which would be equivalent to a 12" or 300mm lens in 4x5. The good news is that if you go to that length, the tessars are more common, but you have to fight for them with the 8x10 crowd, where the 300 is the normal lens (as a 210 or 8-1/2" lens is the normal for 5x7).

But be careful about equivalencies, because field of view is not the only issue. With small format, we tend to hold the camera in our hands, at eye level, and move around a lot. With a large-format camera, we usually put the camera on a tripod, often a bit lower than eye height. It's a different view of the world, and your vision will be affected by it. You might find you don't need as long a lens for 4x5 as you would use for 35mm.

Rick "who likes the tessar look, but some plasmats can make hash of out-of-focus areas" Denney

[Scott Knowles]

I use 3.6 as the multiplier to convert 35mm lenses to 4x5 equivalent. It's not quite the same due to the different images size ratios but it's the closest to approximate the image scene. This was done from comparing images and the actual exposed image size than the film size since both have some film around the edges which isn't exposed. It's works for me.

[BetterSense]

I've never had a plasmat-design lens as far as I know; I have a 90mm Angulon and a Tominon 127 from a polaroid MP-something camera. I'm fairly happy with either one of them except they don't have room for movements. If you say that longer tessars have better coverage maybe I should be looking at a Tessar in this focal range.

What about convertible lenses? Ansel adams mentions using convertible lenses several times in his books. What design are they? It sounds like a tremendous value to basically get two lenses in one, but they don't seem to be popular.

[aduncanson]

As the OP suggests, the ratio of equivalent focal lengths between 4x5 and 35mm depends on focusing distance because longer lenses lengthen disproportionately as you focus closer. As others point out equivalence also depends on whether you are considering negative width, height or diagonal.

Doing the math, here is what I have found:

Subject - Equivalent Ratio
Tight head shot - 2.6 to 2.9:1
Bust - 2.8 to 3.4:1
Full Body - 3.2 to 3.75:1

Calculated equivalent ratios barely change with focal length for a given subject size. The ranges above arise from comparing format widths vs heights. The smaller ratios come from comparing the 36mm dimension of the 35mm frame to the 120mm dimension of the 4x5 negative. While you might always crop your 35mm portraits to the 4:5 proportion, using these shorter ratios is more conservative since they yield a shorter LF lens, which will generally allow you to back off to your desired shooting perspective and get the image you want with only moderate cropping.

Best of Luck - Alan

[rdenney]

I've never had a plasmat-design lens as far as I know; I have a 90mm Angulon and a Tominon 127 from a polaroid MP-something camera. I'm fairly happy with either one of them except they don't have room for movements. If you say that longer tessars have better coverage maybe I should be looking at a Tessar in this focal range.

What about convertible lenses? Ansel adams mentions using convertible lenses several times in his books. What design are they? It sounds like a tremendous value to basically get two lenses in one, but they don't seem to be popular.

Lens coverage is usually expressed as an angle. Tessars are in the range of 54 to 64 degrees, as I recall. So, a lens with twice the focal length will have twice the diameter of coverage given the same design. The 240mm tessar-formula Caltar Type Y that I mentioned will approximately cover 8x10. It will provide abundant coverage for 4x5 unless you are doing something really unusual. 12" tessar-type lenses (Commercial Ektars, Ilex-Calumet, and so on) will be even more abundant--they provide some movement even on 8x10.

210mm lenses were intended as normals for 5x7, so the coverage for 4x5 will be good there, too.

There are some ancient convertible lenses, but they tend to attract collector prices. And there are recent reincarnations of Cooke convertible designs that are also expensive. In between is the Symmar Convertible, which is the first modern version of the Symmar. I have a 180mm Symmar Convertible that converts to 315mm, which might be perfect for your intentions. These are often available for a coupla hundred or less. They were made in the 50's and 60's, and are coated. Mine came in a Compur No. 1, and Compur shutters are probably the most common for these lenses. With both elements in place, you have a six-element plasmat of f/5.6 maximum aperture. With the front element removed, you have a triplet of f/11 or f/12 maximum aperture. The triplet will need to be stopped down to perform well (f/22 or smaller), and you'll need to check focus after stopping down because the aperture in front of the lens will cause a focus shift. And you'll want to be careful were you use the just the rear element because the shutter will be exposed to danger with the front element removed. But the shutters for these lenses had both aperture scales indicated and they provide a lot of flexibility. I think I paid $160 for my 180/315 Symmar Convertible on this forum.

Rick "lots of options" Denney

[BetterSense]

I have a 180mm Symmar Convertible that converts to 315mm, which might be perfect for your intentions.
It really does sound that way. I'll have to keep an eye out for one of those.

[BetterSense]

I picked up a great condition 180/315 symmar convertible from the auction site for $175 with shipping. I'm happy to be effectively gaining two lenses.