Image Circle too small?

[uniB]

Hi all, I'm new here and new to LF - so it's all a bit daunting!

I may have made a boo boo - I've just got a Ebony RSW45 and a second hand Rodenstock 55mm f4.5, I'm now worried that the image circle is too small at 163mm at f22. Is this image circle OK with the 4x5? It's on a recessed board, would it help if it were a non recessed board, will it allow for ny movement or would it be OK at a smaller aperture?

As I say, I'm new to all this so it's all seeming a bit complicated! :confused:

Oh yeah - Can I not use standard filters with this lens either, as it's so wide angle?

Thanks for any help

[Ole Tjugen]

The image circle is enough, but only just.

The image circle is the same regardless of lens board, but it increases a bit with close subjects. Think of the image circle as a cone projecting out from the back of the lens, with the tip at the aperture. when you focus on something close you rack the lens a little bit further from the film, so the cross section of the "image cone" at the film plane makes a larger circle.

[Dave_B]

As Ole said, you lens will work, just. However, a lot of the fun of a large format camera is using the movements to create photos that a standard 35mm camera can't get. This requires a lens whose image circle is much larger than the minimum needed for the format. My advice is to get a cheap, longer length lens. Something in the 150 range would be good for your camera. Play with that lens and learn how all the movements work. A really short lens is tough to learn on as they tend to have pretty minimal movements and are hard to focus well. Also, it is hard to compose a really good wide angle image as it gets very cluttered, fast. As an example, when I backpack and take landscape photos, I have 90, 135, 200 and 300mm lenses. The 135 is my most used lens by a lot. I use the 300mm more than the 90. I have a 47mm lens for my Ebony but have never really gotten a good shot with it. Most scenes have too much stuff in them to really work as a photo.
Good luck,
Dave B.

[JPlomley]

This most recent post should be of interest.

http://www.largeformatphotography.info/forum/showthread.php?t=27857

[Paul O]

Hi. What makes you think the image circle is too small? have you seen results on transparencies/negatives to suggest vignetting? The reason I ask is that I have used the same lens/camera combo and never had a problem. The thing to remember is that the angle of view of the 55mm is wide - the need for any movements is rare. You can, however, employ a few degrees of front tilt without undue concern. I never needed a recessed lens panel either. I did use a 67-77mm step-up ring for filters though.

[uniB]

Thanks for the info everyone, I realise now that getting a 55mm for a first lens wasn't my most successful decision! My reckoning was that I mainly use a 12mm on my dSLR for landscapes so I'd go for something similar. I'll look at getting something that may prove easier to use whilst I'm getting used to the camera.

Glad to hear you've used the same set up Paul O and it's works fine, I have a Cokin X-pro set up for filters, I wonder if these are usable without vignetting with a slim holder?

[JPlomley]

Paul, this has not been my experience with the lens. I am using a Heliopan 67-77 SUR and with a Singh Ray thin mount filter (4.8mm) I see a bit of vignetting. And forget base tilts of more than 2 degrees (accurately measured on my Arca). Front axial tilts even less. Bob Solomon has recommended that a larger SUR (minium 86mm front) is required to circumvent vignetting.

[Brian Ellis]

Hi. What makes you think the image circle is too small? have you seen results on transparencies/negatives to suggest vignetting? The reason I ask is that I have used the same lens/camera combo and never had a problem. The thing to remember is that the angle of view of the 55mm is wide - the need for any movements is rare. You can, however, employ a few degrees of front tilt without undue concern. I never needed a recessed lens panel either. I did use a 67-77mm step-up ring for filters though.

If coverage is close you're better off using back tilt than front. Back tilt moves the film within the image circle so you don't need any more coverage with back tilt than you do without it (well a little in some situations but not much). Front tilt moves the image circle itself relative to the film and so requires a larger image circle.

[David Millard]

[quote]If coverage is close you're better off using back tilt than front.[quote]

While this is very true, the Ebony RSW45 is restricted to using front movements.

[JPlomley]

Just to add to Brians suggestion, you can squeek a bit more rear base tilt out if you drop the front standard no more than 5 mm. Remember, with rear base tilt, the top of the image is moving into the image circle where the coverage is somewhat reduced. To correct for any vignetting, dropping the front standard adds a bit more coverage without sacrifice to the bottom of the image (since it is in a larger part of the image circle).

[uniB]

This image circle business takes some getting your head around!
Trouble is, as David says, my camera, the Ebony RSW45 doesn't have and rear movement at all, only front.
I s'pose it'll mean just using the lens with little of no movement.

[Kirk Fry]

I have found that wide angle lenses are a terrific way to make everything look tiny except my feet. I usually end up using them straight on.

K

[Ken Schroeder]

My Fujinon 105 has the same size image circle. I use it as a lens "wider than the 135. Your 55mm lens is certainly wide. Most of the time you shouldn't need much movement. I would just use it when you want a very wide lens and not worry about the coverage. You can always crop a little if needed.

I believe a more useful first lens would have been a 210. The greater magnification makes everything easier to see, especially when you are just starting.

Ken

[vijayn]

Er, maybe this has been pointed out before, but you can accomplish back tilt by tilting the front standard and then tilting the entire camera in the reverse direction until the front standard is vertical. You'll probably need some shift as well to realign the optical axis. And as with a rear standard tilt, any amount of tilt is possible with the front standard without exceeding the lens image circle provided you use shift as well.

For instance, with a forward tilt and downward shift of the front standard, unlimited tilts are possible while staying within the image circle of the lens. Whether this is useful for the composition is another matter.

[Ken Schroeder]

Look at a depth of field chart....Do you need to use tilt with this wide a lens?

Ken

[Paul O]

Hi "Uni" - I've just realised that it's "my" 55mm that's giving you this headache :(
Lenses such as the 55mm along with the 47XL and even up to and including 75mm focal lengths can be a PITA when it comes to starting out in LF and playing around with /seeing the effect of camera movements. As for things like "image circles" etc then it can get even more daunting. The 55mm is certainly NOT the ideal first lens - BUT hang on to it as it will prove its worth!

I would recommend getting hold of a cheap 150mm lens if you can. The RSW will handle this length of lens and although you may be restricted a bit when it comes to close focussing with it on the camera (limited bellows extension of the RSW) it will certainly help you to "see" the effect of movements that you have applied to the camera.

Back to the lens in question! Hope I'm not teaching you to suck eggs but a brief overview of "image circle" - The image projected by the 55mm lens is a (rough) circle that is in excess of 163mm in diameter BUT the useable (sharp) area of the image is about 163mm in diameter - get a pair of compasses or for less accuarcy draw a circle 163mm in diameter on a sheet of paper. This is the size of the image this lens will produce on a ground glass screen when focussed at infinity. Now cut out a rectangle roughly 9x12 cms from another sheet of paper - this (roughly) represents your piece of 5x4 sheet film. Place the rectangle roughly centrally on the circle you have drawn. This is the position of the film in your camera in relation to the lens with NO movements applied, no rise/fall or tilt. As you can see the circle extends happily outside the sheet of film - this means the lens will cover the 5x4 format. Different lenses have different image circles, some larger and some smaller - the size of the film stays the same but the "coverage" changes. When the image circle is less than the dimensions of the sheet of film is when you find out that the lens wasn't designed for this format! The one lens that springs to mind is the (old) Schneider 100mm Apo Symmar. A frighteningly sharp lens but one designed for use with roll film formats and it had an image circle that was only 145mm in diameter - it couldn't cover the corners of a sheet of 5x4 film. For a lens to cover a sheet of 5x4 film it needs to have an image circle of at least 150 mm as a rough estimate.

If you go back to your drawing of the circle and start to move the sheet of film around within it you will see that the amount of movement is quite restricted before the "sheet" starts clipping the edge of the circle - this "shows" you that the 55mm will cover the 5x4 format but not allow much movement. You also need to realise that as you move the sheet of film closer to the edge of the circle the illumination created by the lens will become less - the image will be darker and this can lead to vignetting - so for best results keep the sheet of film closer to the central portion of the image circle.

But all is not doom and gloom! The 55mm lens is so wide that you can put it on your RSW and centre lens and camera back and when you look at the ground glass and focus at infinity you will see that not only do you have a very wide view, but that even with the lens wide open the foreground is sharp. By the time you stop the lens down to say f16 then you will have everything from the tripod feet to infinity in sharp focus so you don't need to use any front tilt! Great but a bit boring when you want to contort your new camera into all sorts of weird and wonderful shapes, I know!

Its best to think of this camera/lens combo as a wide angle point and shoot. Simply bung it on the tripod, focus far and stop the lens down. Even when using this lens on interior shots the amount of movement needed was MINIMAL -again, almost point and shoot!

With a longer lens like a 150mm you will be able to set the camera up and observe the plane of focus moving as you apply movements - but with a wide lens this is simply too difficult to observe. Most modern 150mm have a big enough image circle to cover a sheet of 5x7 inch film so will allow masses of camera movements before hitting the boundary of their image circle.

I hope this has helped/makes sense and apologies if you know this already :D

If you need any more info/advice feel free to email me!

Next problem - loading sheet film holders! :mad:

Regards Paul

[JPlomley]

Just to add a bit to Paul's excellent explanation and suggestions, here are the hyperfocal calculations for the 55mm APO Grandagon that I have had success in using with the camera zeroed:

Aperture HF Distance (ft)
16 6.2
22 4.5
32 3.1
45 2.2

So for example at f/22, everything from approx. 2.2 ft to infinity will be in acceptably sharp focus. To set the actual HF distance, first note the position for infinity focus, and then extend your bellows by 1/10th the aperture in mm (i.e. f/22 translates to a 2.2 mm extension of the bellows from infinity).

For tilts, the best you are going to do is about 2 degress of rear base tilt. This will require a bit of front fall to prevent vignetting (about 3 mm worth, but calibrate this on your set-up)

Hope some of this helps. The 55 APO Grandagon is my first ultrawide as well. It is worth persisting as it is truly a stellar performer optically (comparable to my 135 Sironar-S)

[JPlomley]

O.K, so the formatting went haywire when I posted my nice little table. The first number is aperture and the second HF distance.

[uniB]

Paul - what a small world! thanks for the information, your explanation is considerably easier to understand than the book I was reading, or maybe the info is finally filtering into my head! I went out today and had a play with the lens on the camera and practiced focusing with a lupe and although it gets mighty dark towards the edges at least I can do it.

I've now managed to get a 90mm and 135mm at a reasonable price so I can practice more with camera movement - as you say, I now need to overcome the joys of film loading!

JP - thanks for the focusing tips, this is one thing that's confusing me a little, the focusing to infinity - with my 35mm and medium format work I always used hyperfocal focusing for my landscape work but was wondering what the score was with LF - so your info is most valuable. I've now spent a couple more hours reading up on focusing / choosing f-stops and I'm now so confused I'm giving up and going back to my D200... only joking! :)

[JPlomley]

My pleasure. I have learned so much from this forum and the excellent participants it's the least I can do to give something back from my own experiences.

Enjoy the adventure,

Jeff