Lens question from an old 35mm guy

[riooso]

Hello all, take it easy on me here! I have been into 35mm on and off for 30 years. I got a new Cannon 35mm but it does not have what I want for Landscapes. I am going to try 4x5 LF and am doing ok with the camera body purchase but now the lens.
Some general boring questions that I can not find the answers to after a couple of weeks.

1. Calculated diagonal for a 4"x5" format is 162.6 mm^2 and the published is 156 mm^2,why the difference?
2. In 35mm world a 24mm Canon lens has a view of 65 Degrees but when I look at the equivalent 90mm lens (Schnider 75mm f/5.6) it has a published view of 105 degrees which is a heck of a lot more than 65 degrees.
3. The formentioned Schnider lens has a image circle of 198mm and since the diagonal of 4x5 is 156mm, don't I lose some of my real world field of view? Like 28 percent!

Thanks in advance, I searched for the info but could not find it

Rio Oso

[Nick_3536]

1) Holder masks some of the edge off. Really no different for any format. Measure a 35mm negative exposed area.

2) Which are you looking at an 90mm or a 75mm? Are you sure it's not angle of coverage you're looking at? I don't think any lens company publishes angle of view for LF lenses. It changes with format.

3) No the image circle lets you move things. Bigger image circle allows more movement. You'll still use a 4x5 slice of that circle which is what the angle of view is based on.

[Oren Grad]

1. Calculated diagonal for a 4"x5" format is 162.6 mm^2 and the published is 156 mm^2,why the difference?

4x5" is the nominal size, but the actual image area of a 4x5" negative exposed in a standard film holder is about 96x120mm, which corresponds to a diagonal of 153.7mm.

2. In 35mm world a 24mm Canon lens has a view of 65 Degrees but when I look at the equivalent 90mm lens (Schnider 75mm f/5.6) it has a published view of 105 degrees which is a heck of a lot more than 65 degrees.

The 105 degrees in this context is the angle of coverage, not the angle of view; it refers to what happens behind the lens, not in front of it. Think if it this way: the lens has to project a cone of light large enough to cover the piece of film you put behind it. The shorter the focal length - the closer the lens sits to the film when it's in focus - the wider the angle the cone has to cover in order to project an image large enough to cover the film. So with wide angle lenses like the Super Angulons and Grandagons, you can expect to see large numbers like 105 degrees. For "normal" lenses like the Apo-Symmars and Apo-Sironars, which sit relatively further away from the film when they're in focus, the required cone is narrower, and accordingly they have coverage angles like 72 degrees and 75 degrees.

The reason nobody ever worries about this in 35mm is that the film size, and thus the angle of coverage required, is absolutely fixed. However, many different film sizes are in use in large format, so for a given focal length you need to know the angle of coverage, or the corresponding image circle, to know whether the lens will project an image large enough to cover the film size you want to use.

3. The formentioned Schnider lens has a image circle of 198mm and since the diagonal of 4x5 is 156mm, don't I lose some of my real world field of view? Like 28 percent!

You do use only part of your field of coverage, but that's a feature, not a bug. One of the advantages of large format cameras is that they generally allow you to shift or tilt the lens relative to the film in order to change the plane of focus or adjust perspective. However, to do that without vignetting the image, you need a lens that projects an image circle larger than that needed to cover the film. If you think again about the Canon EOS 35mm system, there are three special-purpose "TS" lenses - 24, 45 and 90mm - that allow for some tilt and shift movement. These lenses also project an image circle larger than is required to cover the film, in order to allow for the movements without causing vignetting.

Hope this helps - good luck with your explorations!

[Bruce Watson]

Nick and Oren have pretty well answered your direct questions. I'm going to answer one that you didn't ask, but that I wish someone had told me when I was in your shoes asking the questions then that you are asking now.

That is, the lenses you use in 35mm likely will not translate to the lenses you use in 5x4. The two different types of photography are just too, well, different.

I think the primary reason is that when using 35mm, most people put the camera up to their eye and frame with their feet. If you need to be closer to fill the frame, you move forward, etc.

In 5x4 or any other large format for that matter, this is difficult if not impossible to do. What I and many others have learned to do is to walk the scene without the camera. What I'm looking for is the correct perspective that will let me frame the scene the way I want. Then I setup the tripod and put the camera on it. Then I pick a lens that will give me at least the scene I'm interested in on the film for the format I'm using. I very rarely move the camera once I set up the tripod.

What happened to me is that I found myself using lenses that give me angles of view that I never wanted in 35mm. I don't know how I could have anticipated that LF photography would change the way I work like this. Yet, it has.

What I suggest to anyone just starting out, is to buy a 150mm lens for 5x4 and use that for a while until you gain a "feel" for how you work in 5x4. Add lenses from there. I know, I know, you never used a "normal" lens in 35mm. Neither did I. But now I use a 150mm lens for about 1/3 of my work, something I never would have considered when shooting 35mm.

Something to think about in your copious spare time ;-)

[Leonard Evens]

1. The film area is actually slightly smaller than 4 x 5 inches since the film holders encroach. There are some differences, depending on the holders. I find my holders are close to 95 x 120 mm. The diagonal of that is 153 mm. I don't know where you found 156 mm, but it is fairly close. Usually 150 mm is considered the normal focal length for 4 x 5 format, and it is pretty close to the diagonal of the frame.

2. We don't have to appeal to published specifications. We can calculate the angles of view. Using a diagonal of 150 mm, the angle of view of a 90 mm lens is 2 x arctan(75/90) which is just about 80 degrees. Using a diagonal of about 43 degrees (for 24 x 36 format), the angle of view of a 24 mm lens is is just about 84 degrees. So using diagonals they are pretty close. Of course you can calculate the angle of view using something other than the diagonal. But even if you use the long dimension (36 mm), you still get about 74 degrees, so I don't know where 65 degrees would come from for a 24 mm lens. Check again.

In any case, a possible explanation of the 105 degree figure for the 90 mm lens is that it is not the angle of view, but the angle of coverage. Large format lenses are designed to cover a circle larger than is necessary to cover the format. That alows movements, called rises and falls in the vertical direction and shifts in the horizontal direction, without losing definition in the image. It also allows tilts and swings which may shift the lens axis away from the center of the frame. (But if, as you say the image circle has diameter 198 mm, that would in fact correspond to an angle of coverage of about 95 degrees, so the 105 degree figure is still mysterious.)

3. The 198 mm for the 90 mm lens is the diameter of its image circle. Since the diagonal is a little over 150 mm, that gives you about 48 mm leeway, but of course you can only use half of it, or 24 mm, which you could do along the diagonal. You usually shift vertically or horizontally, which would result in smaller shifts, but still there is a reasonable amount of possible movement. You should draw a picture of a circle of diameter 198 mm, cut out a frame of size about 95 x 120 mm, and move it around inside the circle to get some feeling of what you can do.

It should also be noted that the circle has that diameter when focused at infinity. For closer subjects, it would be larger, but that wouldn't make a noticeable difference unless you got reasonably close. Also, if you used the lens to project a circle on a wall, you woul see something that got dimmer and blurrier on the circumference and would be larger than 198 mm. The figure given by the manufacturer restricts you to the region where they consider the resolution and illumination adequate. Even so, with a 90 mm lens there is significant drop off in illumination towards the circumference. In most photography, this isn't obvious, but in crucial situation, for such a wide angle lens, it has to be corrected by a special filter called a center filter.

[Richard Kelham]

2. In 35mm world a 24mm Canon lens has a view of 65 Degrees

I think you'll find your 24mm Canon lens has an angle of view of 84 degrees, not 65...unless you're using small format digital (shock! horror!).

[Leonard Evens]

It has already been alluded to, but let me reiterate that simply comparing the angle of view using diagonals can be misleading. First, the aspect ratios are different, so it isn't clear which dimensions, the short, the long, or the diagonals, should be compared. More important, most large format photographers will use rise, fall, or shifts to some degree, so the center of the frame is seldom the center of perspective. That makes an enormous difference. In the 35 mm world, you can accomplish something of the same kind by cropping, but given the small size of the image, 35 mm photographers usually attempt to use the entire frame. In addition, there are the important aesthetic differences that Bruce referred to.

[Gordon Moat]

One thing you might want to reconsider is that using a wide lens as a start in 4x5 could make things tough. It is harder to focus a 90mm or 75mm on the ground glass than it is a 135mm, 150mm, 180mm or 210mm. At least as an introduction and learning stage, starting with a focal length greater than 75mm or 90mm might be better. If you find you later don't like the more normal lens, you can often sell these for near what you get them, if you shopped carefully and bought used.

Movements are a little tougher to understand. If you had a shift lens for your Canon, it might be easier to visualize. Just as an example, let's say you wanted to photograph a building. If you stood at ground level, then used a really wide lens to get all the building into the image, then the top of the building might look like it was falling over. You could try the same shot with a super wide lens, hold the camera (or on a tripod) keeping the camera back parallel to the building, then have straight sides on the building; unfortunately your shot might then include lots of foreground, meaning you might want to crop. A shift lens, or shift movement on a 4x5, means that you could keep the building sides straight, and avoid most of the unwanted foreground; which is possible without having a superwide lens. The reason I point this out is that while you might like using a 24mm on your Canon, you might find that a longer lens than a 90mm might actually fit better into what you want to photograph.

Tilt is more often used for landscape images, and is something to think about with lens coverage. In practice you would often not use much tilt or swing, nor even much shift movements. Some camera companies find it interesting to show cameras nearly twisted into a pretzel shape in their ads, though it would be rare to ever use that much movement. So when looking at different cameras, try not to put too much emphasis onto differents of maximum movement amounts. Quite likely the more important aspects would be minimum extension for using a wide lens like a 75mm, and how much extension possible for longer lenses. There are also bag bellows and recessed lens boards, and some cameras that allow changing the bellows.

If you want a preview of what lenses to consider, here is an experiment you can try. Take a piece of cardboard, and cut a 95mm by 120mm rectangle out of the center. Then go somewhere you think you might like to photograph and look through the cutout. Move the frame forward or backward a distance from your eye to see how you might like to view the scene. Then roughly measure the distance from your eye to where you are holding the board. While a wide or superwide lens might be beyond your field of vision, this exercise can be good for visualizing.

Whatever you do, try not to get too hung up on technique or technical aspects. Learn to pre-visualize, take your time, and most of all enjoy what you are doing. Best of light to you.

Ciao!

Gordon Moat

[Kirk Fry]

So all of the above and don't get too concerned with comparing with 35 mm. 150 mm is kind of "Normal" but a lot of folks start with a 210mm. This works out to the the ever popular size of 80-85 ish mm in 35 mm. I was where you were 35 ish years ago. I made the mistake of going to an Edward Weston (Cole Weston prints of his Dad's negatives, I am not that old) show at UCLA. Clearly 35mm was not cutting it. I rounded up an old Calumet 401 and a beat up 210mm Sironar and blasted away. I only had one lens for a long while. Helps to not have too many choices. Cheaper too. Anyway I eventually bought a 90mm Angulon and that was very different. I quickly learned that other than rise, I almost always shot the thing straight ahead. Later on I got a Nikkor 300mm M that I liked very much. After that I filled in the missing areas from 600mn down to 75mm and never know which lens to grab. I am building a 4X10 back for my ARCA now. The 150mm gets used quite a bit. So get a 210mm or 150mm and blast away. Don't worry too much what the exact equivalent is in 35mm. After a couple of hundred pictures you will know what to buy next or have decided that LF is too big a pain in posterior to bother with. What is wonderful about LF is that you can really do it on the cheap to the point where you know you like it. Good Calument CC401's can be had for less than $100 and a good used 210mm for $250 and the associated other stuff (black cloth, loupe, light meter, film holders and developing pans, tripod) for not too much. I mostly just shoot landscapes mostly to just entertain myself. I am sure glad I don't have to make a living doing it. Get Steve Simmons' book "Using the View Camera." It talks about all this...... The key thing is to just get out there and do it.

[Michael Daily]

Borrow what you can. Get used if you can. Start cheap and don't rush. The old masters often did what they did with, by today's standards, fairly primative equipment and techniques. Remember: A good photographer can make a good image with whatever is available. A bad photographer cannot. To paraphrase chairman mao: The journey of a thousand images starts with one--not a ton of expensive equipment. Enjoy.
Michael