Wide-angle Adapters on Large Format Cameras

_T_

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Would it be possible to use a wide angle adapter in front of a large format lens?

Many such adapters are made for use with smaller format cameras but often they have the effect of reducing quality at the edges of the image.

But with large format lenses it’s possible to use only a small portion in the very center of the image circle. Would that work towards the advantage of using such an adapter in this way?

Large format lenses are also often limited in aperture to somewhere around f/5.6 and lenses with wider apertures can be very expensive. But with a 0.5x adapter your f/5.6 could shoot at f/2.8. A two stop improvement in aperture is pretty common for the adapters I’m seeing available.

And at an effective f/2.8 you could get some really strange looking shots with very shallow depth of field in a wider field of view than people are used to seeing.

Are there any reasons why trying something like this won’t work? Any downsides that might need to be foreseen? Any tips on getting the best possible results from doing this?
 

grahamp

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Most of these adapters have some physical depth, so on normal to wide focal lengths there is a chance of mechanical vignetting. Depending on the quality and intended use, you will probably see some barrel distortion on wide converters, and maybe even pincushion on long converters. Adding extra optical surfaces in front of a decent lens in not likely to improve it (entropy rules!).

Why do you want to do it?

a) effect, even at the cost of quality
b) to get a wider or longer lens than you have?

For long converters, the result has to be better than the effect of enlargement, and at 1.5x to 2x, that is not likely.
For wide, you will not get a true wide.

I actually tried this with a Mamiya TLR (6x6) using a reversible 0.5x/1.5x unit with 46mm thread (the largest Mamiya thread is 49mm). With the 55mm wide on the Mamiya (say 90mm on 4x5) I got a circular image in the 6x6 frame that was wide, but not what I would have expected from 55/2 =27.5mm.

As a long converter, the resolution was nothing like as good as simple enlargement.

Unless you can get a converter with a size that matches the filter ring on the lens you want to try, vignetting is inevitable.

I went in with low expectations, and I wasn't disappointed!
 

Dan Fromm

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_T_ said:
And at an effective f/2.8 you could get some really strange looking shots with very shallow depth of field in a wider field of view than people are used to seeing.
Click to expand...

No reason why not, but adding an afocal attachment in front of the lens won't change the f/ number. Metabones (https://www.metabones.com) makes what you want, but not for LF lenses and pricey.
 

JPD

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xkaes said:
Of course you can -- in ways you never imaged!!!

http://www.subclub.org/fujinon/close-up.htm
Click to expand...

For plate cameras with fixed lenses, Schneider had their Jsco Verkürzungslinsen, and Zeiss their Proxare for this purpose. Simple positive meniscus lenses, same as close-up lenses. When plate cameras with fixed lenses went out of fashion so did the use of these lens attachments, but they were still sold as close-up attachments.
 

JPD

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grahamp said:
I assumed the OP was talking about wide/tele adapters like those made for some Bay 1 TLRs, fixed lens 35mm, and video cameras, not close-up, because of the reference to 'wide-angle'.
Click to expand...

The wide and tele attachments for plate cameras were positive and negative meniscus lenses. With bellows you can easily adjust the focus. For other cameras, like Rolleis, you need something else because the lenses have a hard stop at "infinity".

The Zeiss Proxar and Distar lenses were originally made as wide and tele attachments for plate cameras, and other manufacturers had theirs. Verkürzungslinsen/Verlängerungslinsen, Curtar/Longar by Agfa and Schneider, Deltalinsen by ICA...

The negative meniscus lenses for increasing the focal length weren't made anymore since plate cameras with non-interchangable lenses went out of fashion (and production), but the positive meniscus lenses still had a use as close-up lenses for other types of cameras.

What we see today as close-up lenses only were actually sold and used as wide angle attachments. Of course, they don't convert the lens into a "true" wide angle, but only shorten the focal length. But they were handy.

Zeiss publications about the Proxar and Distar:


 
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grahamp

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Always something new (or old, I suppose), to learn!
 

xkaes

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JPD said:
Yes, but it's not quackery. I'm looking for certain negative meniscus lenses to turn 13,5 cm plate camera lenses into short "teles" for portraits.
Click to expand...

Those NEGATIVE lenses are harder to find -- in threaded "filter" rings, ready to go -- but they are out there. At least with wanting a longer FL, you can always crop -- unlike with wanting a shorter FL.
 

JPD

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xkaes said:
Those NEGATIVE lenses are harder to find -- in threaded "filter" rings, ready to go -- but they are out there. At least with wanting a longer FL, you can always crop -- unlike with wanting a shorter FL.
Click to expand...

Yes, and the "rarity" make them fun to chase. I think they are more common in push-on mounts. True about cropping, and you don't lose much image quality when cropping a large negative.
 

xkaes

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I was in need of some "weak", POSITIVE, meniscus, single-element, close-up lenses -- 0.5 and 0.25 diopters. These are not easy to find, but they are available, at least on the used market. I had to settle for slightly larger sizes than I wanted, but it was worth the hunt.
 

Neil Poulsen

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It would be pointless to use wide-angle adapters on a large format camera, because it would narrow the image circle. So, it would be a limitation on movements.

That said, I have a Horseman attachment that does the opposite. It converts a 150mm lens to a 300mm lens. Versus the front, it attaches behind the lens.
 

JPD

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Neil Poulsen said:
It would be pointless to use wide-angle adapters on a large format camera, because it would narrow the image circle. So, it would be a limitation on movements.
Click to expand...
The Proxar type positive lenses can be handy for emergency use when you need a slightly wider angle. And they don't take up much space. They aren't optimal, of course, but when you have a plate camera with a non-interchangable lens you can't just replace the Tessar with an Angulon without tools and time.
 

xkaes

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Neil Poulsen said:
It would be pointless to use wide-angle adapters on a large format camera, because it would narrow the image circle. So, it would be a limitation on movements.
Click to expand...

It's not pointless at all because it depends on the image circle of the lens, and the strength of the close-up lens being attached.

The image circle created by the lens will decrease when a close-up lens is added, of course, and the stronger the diopter, the smaller the image circle will become. And if the image circle shrinks enough, you are likely to lose the corners of the image. This is especially true if the lens -- without the close-up lens attached -- has a small image circle to begin with.

But if the lens has a large enough image circle, and/or a relatively weak close-up lens is being used, there will be very little loss in the diameter of the image circle.

Formulas for computing this can be found at:

http://www.subclub.org/fujinon/close-up.htm
 
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_T_

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Neil Poulsen said:
It would be pointless to use wide-angle adapters on a large format camera, because it would narrow the image circle. So, it would be a limitation on movements.
Click to expand...
That does appear to be the limiting factor.

My widest image circle is my fujinon ws 180mm f/5.6 which has an image circle of 305mm at f/22.

Unfortunately that means that with a +1/2 diopter I would get a 90mm f/2.8 with an image circle of only 152.5mm at f/22. Which means I wouldn’t be able to shoot wide open at infinity.

But what I actually want to do is shoot people in very blurry environments. Which would mean I would focus closer and get a larger image circle.

I’m still not sure it would work. The image circle when focused for an upper body shot would be only about 158mm @ f/22 but I have no idea what the angle of coverage is at max aperture so I can’t calculate the actual image circle.

But a 90mm f/2.8 on 4x5 produces an equivalent image to a 25mm f/0.8 on 35mm so i think it should still produce the effect of unusually low depth of field for how wide the lens is if I need to crop out the corners a bit.

And I’ve seen some of these diopters going for something like $40. So it wouldn’t hurt much if I try it and find out it’s not going to work.
 

xkaes

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I have no idea how you came up with those numbers. A 180mm lens with a #0.5 diopter CU lens creates a 165mm lens. A #1 diopter CU lens gives you a nice 150mm -- and stopped down to f16 will give you great results with little loss in image circle..

 
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_T_

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I guess I did all my math wrong. I was thinking that the 0.5 diopter referred to the a 0.5x change in focal length when applied to my lens.

I have now read the equation to calculate the change in focal length and understand it. Just wasn’t thinking.

I have to start all my planning over now.

Edit: sorry I was so bummed out by having to redo everything that I forgot to thank you for setting me straight. Thanks! Your help is greatly appreciated
 

xkaes

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_T_ said:
And I’ve seen some of these diopters going for something like $40. So it wouldn’t hurt much if I try it and find out it’s not going to work.
Click to expand...

I wish I had a nickel for every math mistake I made!

Anyway, as the table shows, a low diopter CU lens can make a significant change in the FL of a lens -- with very little loss in IC. And there will be little loss in quality if the lens is stopped down. The IQ loss can be reduced even more by employing an achromatic CU lens -- these are more expensive, of course. Here's the best list I've seen:

http://fuzzcraft.com/achromats.html
 
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_T_

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Excellent link! That difference is astounding.

Turns out I already have one of the sets that’s been verified on that list. The one made by Opteka.

And as it happens the set is the exact size I need for my Fujinon 180mm. So I’m all set.

My vintage gear hoarding has been vindicated.

Thanks again for all the help!
 

xkaes

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Hold on a second. I've got that Opteka too -- great CU lens, but that is a #10 CU lens. That would turn your 180mm into a 65mm lens -- look at the table. I use the word "would" because that combination won't work. Try it and see for yourself -- assuming your bellows can collapse that much. You'll end up with a 65mm lens with an image circle of 110mm (assuming no additional physical vignetting). That might be OK with you if you don't mind cropping, but the quality????? That's "pushing the envelope" for sure.
 
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_T_

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So I’ve got a +1, +2, +4 and +10.

The +10 won’t work. The image circle limits me to macro or near macro stuff.

So I tried the +4 and it’s exactly what I hoped. The angle of view is wide enough to capture the surrounding environment and the depth of field is shallow enough to look weird af. Like a totally sharp person surrounded by an unnaturally blurry world.

I even have about a cm of rise if I need it. The image circle doesn’t suddenly cut off it sorta fades away into poorer image quality and a very gradual vignette so I could get a little more than that if I accept the consequences.

But yeah pretty much exactly what I imagined.

I’m about to go do all the calculations to see what I actually have in terms of physical specs.

I am wondering though, can I combine these diopters? Like say I use both the +2 and +4 together, would that be the same as a +6. I imagine it would degrade the image somewhat but it would give me a little more flexibility in choosing my focal length.
 

xkaes

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I was unaware that they offered a +!, +2, and +4 -- so you've got quite an array to work with. You can add them together -- you'll get slightly better results by screwing in the STRONGER CU lens first, and much better results by stopping down.
 
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