Wide Angle Lens versus Distortion? Tradeoffs?

[johnw436]

I have been spending a lot of time shooting the interiors of

churches, and most recently stained glass windows. I am constantly

plagued by the Big Subject - No Room to Back Up syndrome.

 

I'd really like some advice from you all. I appreciate all the

knowledge and experience I have gotten to listen in on via these

forums. You all have been a great help to me.

 

I'm using a Bronica ETRS, usually with the 75mm normal lens. My

question is whether a 40mm or 50mm wide angle would be the most

useful. I'd hate to sink a lot of money into a 40mm or even a

fisheye only to discover that the lens distortion makes most of the

additional image unusable. How much more distortion would I get from

the 40mm than I would from the 50mm?

 

I have been learning PS as a necessity for perspective correction

already, and I don't mind saying that I'd much rather get it right in

camera than spend a lot of time in Photoshop. (Remember that I am

fairly inept at PS.)

 

Is a fisheye even worth considering for interior shots? I am not

after artsy effects.

 

Is there a tilt/shift lens available for the ETRS? Would it be worth

using if there was?

[mike_earussi1]

When you can buy a good used 40 at KEH for around $265 it's difficult to think in terms of "sinking a lot of money" into it. Bronica 645 equipt. is so cheap now that you could probably afford both.

[Ed_Ingold]

Distortion (ie. barrel distortion) at the corners is about 4% for a 40mm Hasselblad lens, compared to about 2% for a 50mm lens. I suspect Bronica lenses are similar. This is still reasonably low, and of no consequence for landscapes or portraits where straight lines are not prominent. It is not excessive for architecture, at least for non-critical applications.

 

I suspect you are confusing perspective issues with distortion. Perspective is a function of camera to subject distance. With a wide angle lens, perspective causes nearby objects to be exaggerated. This effect is precisely why wide angle lenses are used.

 

Vertical convergence is also exaggerated if the camera is tilted from vertical. This is problematic for photos of buildings and interiors. To avoid vertical convergence with an Hasselblad, you must keep the camera level, use a shift lens (PC Mutar), Arc-body Flex-body, or correct it in Photoshop. I don't know if the Bronica line includes a PC lens or adapter. Perspective correction is not that hard in Photoshop - a little homework would pay off.

 

A Fisheye lens deliberately introduces large amounts of barrel distortion. This effect is easily overdone and not easily corrected, even in Photoshop.

[fernando_libenson]

Due to lens design limitations to allow room for the mirror, every wide angle lens for a SLR camera will have some degree of distortion; with that in mind, imho the best choice for your specific purpose would be a rangefinder. In the MF world, you have several options, like a Mamiya 6 or 7, a Fuji GSW690, or the cheaper old Fujica G690, or a Mamiya Press, all of them of very high quality.

I hope this helps.

[OCULUS New York]

John, As an architectural shooter too, I feel your pain. Sure, a wide will give you more coverage, but it has its limits too. I would suggest a couple of things, that you probably already know, but they are worth mentioning.

 

1. You must keep your camera level and in a parallel plane with the wall, window, etc. And the wider your lens, the more distortion you are going to get if you elevate that front.

 

2. If you can't back up, GET up--use a ladder. To shoot the Tiffany rose window at the rear of our church we use a very tall step ladder in front of the altar, and a long lens. Otherwise, it's all parallax problems that PS won't touch.

 

3. Consider a shift/tilt lens. I use a wonderful Schneider PCS 55mm on my Rolleiflexes (aka the "Horned Monster" http://d6d2h4gfvy8t8.cloudfront.net/2013455-lg.jpg and it is really beneficial. It lets you use shorter ladders ;->

 

4. Otherwise, you'll have to find a large format setup that doesn't break the bank or your back.

 

Good luck,

Ray Hull

[stephen hazelton]

A fisheye is worth considering for interior shots IF you like that fisheye look. I wouldn't buy one intending to "defish" all the shots digitally.

 

Some of it depends on what you are trying to do. For very formal-type architectural work, you'd probably want a view camera. Otherwise, buy the widest rectilinear lens you can afford and go for it. With most shots, distortion due to the lens (ie, barrel distortion, pincushion distortion) is not significant. Perspective distortion (close things look bigger, etc) is significant, and dealing with that is just a part of shooting with that lens.

[johnw436]

First, thanks to all of you for your help.

 

Please allow me to clarify, though. After re-reading my post I see that I crammed three separate issues into one question.

 

My biggest problem is field of view. I am trying to get a lot more church into the scene than what my current lenses allow. A wideangle of some sort is the obvious answer, but not if barrel distortion warps the image to the point that the extra field of view on the image is unusable. The ladder idea is a very good one. Whenever that is practical I will definitely pursue that.

 

Knowing that there will be lens distortion, my question then becomes "will a 40mm lens distort enough that there is no benefit over a 50mm lens?" I know that on the Bronica a 50mm is about a 28mm-equivalent for 35mm format. That's pretty good considering my 75mm normal lens is about a 50mm 35 format equiv. I understand that the 40mm would give me the 35mm-format equivalent of a 23mm. That is not really a significant improvement if all my verticals are going to be warped into unusability. Hence the fisheye question. I've never used a fisheye before and now it sounds like it wouldn't get me anywhere. LOL...yes, I was planning to 'defishey' all the images. Really dumb idea now that you mention it!

 

Lastly, I asked about using a Tilt/Shift lens for shooting up at stained glass windows. Here, the ladder technique is the perfect solution if that option is available. I agree that perspective correction is fairly easy in CS2. Getting it right in-camera is easier still.

 

Thanks again to all of you for helping me out. I really do appreciate your knowledge and experience.

[jimmy_english]

Schneider made the exact same perspective control lens for the ETRs but they're $600 to $1200 on the bay. I understand there were very few made (maybe only 20 or 30 in the US)

 

Jim

[neild]

If you have the patience, then a longer lens can be used to collect multiple photos which can be later combined into a panoramic image - in either horizontal and/or vetical direction (therefore, the final image needn't look panoramic itself: it could well be square). Thie method has the advantage of not needing any defishing (perhaps some correction for each image to fit the whole composite, but this is not much), and the resolution goes up, not down. This method is ideal for subjects which do not move - like church interiors.

 

Note that you can do this with a T/S lens as well - this may well minimise the corrections needed before you combine the images. Just a thought...

[david_littleboy__tokyo__ja]

Lens distortion in the 645 and 6x6 35mm and 40mm lenses is quite mininal; it's really not a problem at all. The latest version of the Zeiss/Hasselblad 40mm lens is said to sacrifice distortion for improved resolution, however, and may be the worst of these lenses for distortion (while being the best for sharpness and contrast). Maybe.

 

What is a problem is the "keystoning" or "perspective distortion", i.e. if the film plane is not parallel to the subject plane, parallel lines in the subject tilt that you are seeing now. What you can do with 645 is use a 35mm or 40mm lens, hold the camera vertical, and crop out the bottom 1/3 of the image, giving the effect of a moderately wide shift lens on 35mm.

 

If you make a point to minimize keystoning by accepting that you'll crop later, the wider the lens, the easier it is to minimize keystoning, so you want the widest lens possible. However, if you zoom with your feet until the subject fills the frame and then tilt the camera, the wider the lens, the worse the keystoning.

 

I find superwides a lot of fun, and my 35/3.5 on my Mamiya 645 is rarely off the camera.

[martin_fahey]

I'm a bit confused with the comparison between "equivalent" focal lengths for 35 mm and 645 format.

 

I thought you could either compare the horizontal field of view, or the diagonal.

 

Thus, for the horizontal comparison, the 645 negative is 56 mm wide, and the 35 mm one is 36 mm wide, giving

 

50 mm in 645 being equivalent to 50x36/56 = 32 mm

 

40 mm in 645 being equivalent to 40x36/56 = 25.7 mm

 

Using the diagonals (69.4 mm and 43.3 mm respectively) the comparison becomes:

50 mm equivalent to 31.2 mm

 

40 mm equivalent to 25.0 mm

 

(I think some of the conversions in earlier posts are on the assumption that the 645 negative is 6 cm x 4.5 cm)

[johnw436]

Martin,

 

I have no doubt that you are correct. My equivalent numbers did in fact come from earlier posts.

 

Thanks to everyone who answered. It sounds as though the 40mm is the way to go, realizing that any tilt at all will produce a lot of distortion. The reality of most of my shots is that it's usually unavoidable. In most Cathedrals the 'shoeleather express' zoom technique gets me far enough back that shooting altars and domes works fine. Of late it has been the windows giving me a fit.

 

I see a ladder in my future. A very BIG ladder. (...some churches may frown on driving a scissor lift down the aisle...)

[SCL]

John - I don't believe Bronica ever produced a Tilt & Shift/Perspective Correction lens, and since the shutter is a leaf shutter in the lens, that pretty well eliminates uning somebody else's lens on the ETRS, unless you are a pretty experienced machinist and optician. <p> A fisheye would create immense distortion, and I think you would probably be disappointed with the results.<p>

There were some other good suggestions. I use the 40mm lens and like it a lot, very nominal distortion. If I was making a recommendation, I would suggest you either try a 40, or use your current lens, a tripod and panoramic head (Kaiden or Jacobs Engineering) and stitch the photos in Photoshop (yes you may have to use perspective control on some shots in PSCS anyway prior to stitching). Best of luck with your endeavor. You have a great camera to work with.

[jtyr]

Just to set the record straight, Bronica DID produce a tilt/shift in cooperation with Schneider. I own one-- quite a hunk of glass. Supposedly not many were made, but I have seen 5 or 6 so far this year on eBay. Jimmy's post was quite accurate.