6x7 equivalent focal lengths in 35mm

I have a Horseman 980 with a 6x7 rollback and a 105mm lens. I would like to use it for landscapes and

macro/product photography. So, what does my 105mm approximately compare to in 35mm format? What focal

lengths do I need for the 6x7 to approximate the look of 35mm wide angle and 105mm telephoto in 35mm format?

Is that enough 35's and 105's for ya?

Starting with 6x7cm format divide by 2 to get the 24x36mm format equivalent.

So my 105mm on the Horseman is my "normal lens" at what would be approximately 52mm on my SLR?

It's like 55mm in equivalent, aproximately. Most lenses for medium and small but also large formats are not exactly of focal length specified, say 105mm can be any from 97mm to 112mm in reality. The tolerance by top brands is 5 -7%.

Here's a handy memory jog, not sure where I got it from (either my calculator and pencil or 'swiped'). It's not 100% precise, but very close. My 2 cents. Jim M.<div></div>

Very handy table there. I've just purchased a Mamiya M645J with the 80mm lens and was wondering what other lengths might be useful.

Alan, this calculator is the most accurate way of comparing focal lengths especially if you want to compare horizontal angles of view. http://www.mat.uc.pt/~rps/photos/angles.html

The way I do it is to calculate the diagonal of the film frame (remember Pythagorean theorem? :-) ) and compare

it with the diagonal of 35mm film frame to get the focal length factor. So say for 6x7 (which is something like

56x68mm actually):

 

6x7 diagonal = square root of (56 * 56 + 68 * 68) = 88.09

 

35mm diagonal = square root of (24 * 24 + 36 * 36) = 43.27

 

thus the focal length factor is 88.09/43.27 = 2.04 (just like Ellis said + my two (per)cents). 35mm in 6x7 would

be about 70mm in 6x7. The caveat is that 70mm will still have the shallow depth of field just like 70mm mounted

on 35mm camera so the bigger format you should the tougher is to get everything in focus; on the other hand, if

you like selective focus, you'll be happy with 100mm being your normal focal length.

Thanks for all the help with this. The calculator and table are very helpful.

Diagonal fields of view, which are the normal reference, are not the most valid comparisons in your case, as the aspect ratios (height to

width ratio) of the two formats are quite different. 35mm format corresponds really to a 6x9 medium format. Better to use

in this case the horizontal rather than the diagonal field of view, whereby the base of 36mm of the 35 mm frame is about one-half of that of

the 6 x 7 (70mm, but actually a bit less than 70mm, as 70mm is the theoretical frame width and not the practical one measured at the

camera's film plane).

 

Thus, a 35 mm semi-wide angle for 35 mm format should be at most 70mm, prefereably slightly less (or 65mm) in 6x7, as opposed to

75 mm mentioned in the above table. The other numbers in the table above are somewhat better fits.

B&H Photo has a <a href="http://www.bhphotovideo.com/FrameWork/charts/comp_mamiyamed_10.html"> LENS COMPARISON

CHART </a> for Mamiya 6X7 lenses.

It's difficult since the aspect ratio of the format are different.

 

I use a schneider 110mm with 6x7 and it *feels* to be about 55mm equiv. 90mm feels wider than 50mm.

Excellent points about depth of field with 6x7 format. Consider the 35mm camera using 85mm f/1.8 for subject isolation in portraits, the 6x7 portrait lens is often a 150mm f/4. Note that Bronica GS-1 was built to be a lighter 6x7 than Pentax and Mamiya. All lenses are leaf with maximum speed of 1/500 and the lenses are slower f stop which keeps the

lenses lighter and smaller. Fastest lenses are 80mm f/3.5 and 100mm f/3.5. The 150mm is equivalent to 75mm and the 200mm is equivalent to 100mm neither is particularly close focusing thus an 18mm extension tube is used for close headshots.

Wow, this is an old thread.

 

To me, when comparing focal lengths the primary thing that matters is the equivalent angle of view in the long dimension. At least with the way I photograph, it's the dimension that almost exclusively dictates how I'm framing whether I'm shooting in a horizontal or vertical aspect ratio.

 

To that end, in 6x7 I will interchangeably use either a 90mm or 127mm as my "standard" focal length. 90mm is a bit wider than 50mm(about 45mm or so if I recall), while a 127mm is roughly 58mm. On an RB67, as much as an oxymoron as this may be, I prefer the 127mm as a "walk around." Even though I find it a bit constraining(granted I've also used 55s and 58s in 35mm in the same role), weight considerations ultimately win out and my pre-C 127mm is probably half the weight of my K/L 90mm.

 

Since lens weight was brought up, it's also worth remembering that RB/RZ lenses are heavier out of necessity than an otherwise 100% comparable lens for a GS-1, Pentax 67, or even Mamiya 7. The reason for that is that the RB/RZ lenses have to cover 7x7 at a minimum, while the others only have to cover 6x7.

Me too. I use to consider first the long side of the format to make comparisons. Then, I imagine the short side given the aspect ratio.

"To me, when comparing focal lengths the primary thing that matters is the equivalent angle of view in the long dimension."

 

"Me too. I use to consider first the long side of the format to make comparisons."

 

Thank you both, guys!

Not too long ago I was berated for suggesting that using the format diagonal was an absolutely ridiculous way to compare focal lengths. After all, who tips their camera at a jaunty angle to take in more subject width?

 

Also, if you compare "standard" lenses across different formats and aspect ratios, you'll find a close match in their long-side angle of view. Not so much in their diagonal AOV.

The only time comparing diagonals makes sense-at least to me-is when you have the same aspect ratio. Comparing them on APS-C DSLRs to 35mm or 4x5 and 8x10 would be examples of that.

 

Even at that, though, the horizontal dimension(or the vertical dimension) works just as well. i.e. a 300mm lens on 8x10 covers the same as a 150mm on 4x5.

Jim Momary's table is as good as any I've seen. I'm normally a stickler for details, but in the case of equivalence between formats with different aspect ratios, close is good enough. the best lens is the one which suits your needs for composition, working distance, etc. To argue whether horizontal, vertical or diagonal field of view is better is simply straining gnats.

 

* that expression comes from my grandmother, who canned a lot of fruit. I suspect the gnats got through the strainer, despite your best efforts.

"...but in the case of equivalence between formats with different aspect ratios, close is good enough."

 

Very true! There's little point working out that you need a 43mm lens if nobody makes one in your camera fitting.

 

Having said that, there's also not much point in taking the diagonal or short side of a format like 6x17 as any sort of comparator reference. Or of using the diagonal of 6x6 either.

 

Where it does matter is when space is limited. For example; I know off the top of my head that a 17mm lens on 24x36mm has a horizontal AOV of just over 90 degrees, and that if I back the camera into a corner I can take in almost all of a rectangular room. I have almost no idea what the eqivalent lens is on other formats, so I need to do the maths based on the long side dimensions. The diagonal or short side of the frame really don't interest me in this case.

Edited June 6, 2017 by rodeo_joe|1

The diagonal dimension is traditionally close to what is considered a "normal" lens for a particular format. In practice, that is rounded off to 50 mm, 80 mm and 90 mm for 35 mm, 6x6 and 6x7 respectively. Even that is a loose definition, because for many, 35 mm is the lens they "normally" use for 35 mm film, 75 mm and 105 mm respectively.

 

Part of using a camera is learning to "speak" its language, which includes using the controls without thinking and choosing a lens. The reasoning behind equivalency of lenses for different formats is because most of the last two generations of photographers have grown up with 35 mm film, and intuitively "think" in focal lengths related to that format. After using a medium format camera on a regular basis, you no longer thing of equivalency. You look at a subject and choose the appropriate lens for its own sake, not what you might have selected for an SLR. You also tend to compose to make use the the fatter aspect ration afforded by medium format, even square format, compared to the skinny 3;2 35 mm frame. Actually the same phenomena accompanied regular use of a unique camera like the old "Veriwide" I used in my days at a newspaper.

 

The only medium format camera I used at that time was a Rolleiflex with a 75 mm lens. Equivalency is moot when you only have one lens at your disposal. The "tough" choice was whether to use a 35, 50 or 90 with my Leica, or 90 or 135 with a Speed Graphic. More recently in windy, dusty Iceland, I was reluctant to change lenses outside the protection of the car. An early decision was made, "Is this a 16-35, 24-70 or 70-200 moment?" I kinda' gave up on swapping primes in these circumstances. Waking about in the city (Reykjavik) with streets barely wide enough for a car with rear view mirrors, the choice was easier - 25 mm. I have never considered medium format a "walking" type of camera.

The only medium format camera I used at that time was a Rolleiflex with a 75 mm lens. Equivalency is moot when you only have one lens at your disposal.

 

I agree with this to a large extent.

 

My first adventures into MF were burning up a LOT of film in either a Rolleiflex or Rolleicord(I know I went through at least two 20 roll boxes of Provia along with who knows how much Velvia, Tri-X, and some other sldie and color negative thrown in along the way). I have a 75mm on both cameras(I was low budget back in the day, so had 3.5 Tessar/Xenars) and worked only with it. I still managed some great photos, or maybe at least passable ones :)

 

When I got my first job, I decided it was time to "graduate" to an SLR but bought my Bronica SQ-a initially with only an 80mm and used it that way for a long time. The most exciting thing to me was that I had a lens that was a half stop faster. In fact, that's still the only lens I have for it, although I'm eyeing a 40mm. I have other systems where I have wider and longer lenses.

 

Even though I have a TON of 35mm primes, I tend to have a "3 lens maximum" rule when I go out. My usual kit is a 20mm 2.8, 50mm 1.4, and 135mm f/2. Depending on specific situations, the 20mm sometimes loses out in favor of the 24mm f/2, and I might bump the 135mm to a 200mm 2.8 or if I anticipate macro work might drop down to the 100mm Macro. Of course, if I'm anticipating being close to the car the list might expand, and if I trek very far or have a specific goal in mind I might drop down to two or even a single prime.

 

My original serious interest in photography arose from a trip to France in high school. I bought a Canon A-1 and a couple of lenses(mostly off brand, since I didn't know/appreciate how cheap and how much better Canon primes were vs. 80s 3rd party lenses), and hauled them all over with me. I had pretty much everything from 21mm to 200mm covered. After a half a day, most of the stuff stayed in the hotel room. I spent the rest of the trip with the A-1, a 50mm 1.8 hanging around my neck, and a few rolls of film stuffed in my pockets. I didn't find it particularly limiting, and it forced me to work with what I had.

I use this picture to show the difference between different format.

For me as mostly shoot landscape now, it feels natural to think in horizontal angle.

If I have equivalent lenses for "all" format, then it is just the amount of sky that varies between the different format.

 

And the table Jim did show gives a good enough value for equivalent lenses.

 

But, as the picture indicates: I never shoot 6X7..

 

Edited June 7, 2017 by reidar_gustafsson

"The diagonal dimension is traditionally close to what is considered a "normal" lens for a particular format."

 

- I think the key word there is "traditionally", as in back in the C19th century when cameras mainly came in 10x8, whole, half or quarter plate. Formats which all have approximately the same ratio.

 

The diagonal is also useful to lens designers and users of large format cameras to decide if the image circle of a lens will cover a given sheet of film. Other than that, it really is a totally silly way to compare lenses across formats with different ratios.

users of large format cameras to decide if the image circle of a lens will cover a given sheet of film.

 

The diagonal of 4x5 is 6.3" or 162mm. This is indeed an important number to keep in mind when lens shopping, but realistically I'm looking for lenses that have image circles substantially larger than this(it's an important enough value that it's usually prominent in the lens specs).

 

As an example, the well regarded Nikkor-W 150mm f/5.6 is listed with an infinity image circle of 174mm wide open and 210mm at f/22. Since LF lenses aren't used wide open all that often, the latter is a more important number.

 

In any case, that guides me on how much I'm going to be able to get out of the lens in terms of movement. Also, within reason, bigger is better as the quality typically starts to degrade at the edges of the circle so ideally I want something that gives me "room to spare" on the movements.

 

All of that is irrelevant on your typical MF camera, though, as we can safely assume that any quality maker has provided more than enough image circle to fully cover the frame and to minimize wide-open vignetting as much as realistically possible.

 

On the subject of the long angle, I'll also mention that even in portraiture I'd consider it more important than the short angle at least in the 645-6x9 range. Peoples' faces are longer than wider, so if taking a head shot you'll usually be fine on the short angle at the 2:3 aspect ratio or less. This is even more true when you start including more of the person's body since, again, most people are taller than they are wide.

I don't recall ever consulting an equivalency table when shooting a portrait. Regardless of the film or format, I make it a point to stay at least 5 feet from the subject, if I want the subject to look best rather than satisfy some artistic whim. For that matter, I don't consider equivalency when shooting landscapes or anything else either. I pick a lens that works.

 

The only time equivalency is an issue is when you're buying equipment with which you're functionally unfamiliar. Even then, you're more likely to consult others who have real experience, including via the internet. The field of view is proportional to whichever dimension you use to compare two lenses - focal length, diagonal, short side or long side. Much ado about NOTHING.

 

In my experience, not many lenses have an image circle that actually covers the format when wide open. That's why we consider "vignetting". It's a matter of degree rather than kind.

Edited June 8, 2017 by Ed_Ingold