First medium format purchase

[Dug]

Getting back to your task of photographing furniture with a pleasing perspective.
I take it that in your example comparative focal lengths you use 24mm on a DSLR (FF), so I'm figuring you want to photograph the furniture in a domestic setting that is a bit of a tight space.

If you can get access to someones larger living space that you could get further back with a longer DSLR lens it might be your solution right there.
For that extra quality you want, renting a Canon 5DS @ 50 megapixel for the session is going to have that covered over your 5D @ 12.8 megapixels.

6x7cm film is all very well but you need to scan the result these days to use the image in printed and digital media for wide distribution if these pictures are for promotional purposes.
I'd go with an image straight from camera over a scan any day.

A lot of assumptions here.

If you have your heart set on doing med format film then just go for it. The equipment has never been cheaper.
Can't say the same for film and from film printing costs though.

My 6x4.5 film camera sits on the shelf for that reason and I was always disappointed with not having the same control over colour print out come as I now have with digital.

[mongo]

Mongo is not going to get into this argument other than to say:-

- Mongo has used a MF for many years and still owns one
- Mongo agrees with those who have said to you that MF will not make a difference for the reasons you are looking to use it for (and many good reasons have been given to you as to why MF will not necessarily solve your perceived problem)

Good luck with your final decision

[Dug]

I should point out first Ben that as is often the case on photographic forums, posts can turn into a nerd fest and it is not our intention to tell 15 different ways that we are not in agreement with anything you have said or quoted.
It is all in good fun and in the spirit of learning new things and delving into unfamiliar territory.

So anyway I found this field dimension and angle of view calculator thingy.

Into the values I have put the sensor size for a 6x7 camera and for 35mm
I have used 50mm focal length for the 6x7 and 24mm for the 35mm
2m to subject has been used for both calculations assuming you where after a relatively tight framing of a single seat couch chair as an example.

What I intemperate from the results is that though the figures differ in the results window for horizontal, vertical and diagonal values, the 6x7 for example has slightly smaller values in the horizontal and slightly bigger in the vertical and the diagonals average out closely.
This is because the 6x7cm has a different aspect ratio to the film frame than 35mm, 6x7 has a closer to square ration and 35mm is more panoramic by comparison.

On average you would stand at the same distance from the subject with with each of the example camera lens combos and get the same result.
What would give credence to what you read about medium format is that medium format cameras tend to have more head room in the shape of the frame compared to 35mm and therefore with the right shaped subject you could move a bit further back without chopping the top off anything.
This would change the perspective a bit, more so the closer you needed to be.

35mm calculation



6x7cm calculation

[jjphoto]

...Could the angle of view be measured from the lens nodal point in which case it is irrespective of sensor/film size?

It's my understanding that this is the case, however there are two nodal points in every lens (because the lens has two sides and effectively can be used in either direction although obviously with a different result).

...
I think it would be useful to identify we're not talking about things like barrel/pincushion/moustache type distortions which are related to lens design.
For lack of a better term, it's 'perspective distortion' that's the subject of contention here. The type you see between a wide angle vs telephoto lens. If there's a better term for it, please let us know...

Re perspective distortion. Whether or not there is 'distortion' in the final image depends on the size of the print and viewing distance relative to the perspective in the original image. The reason images shot with wide angle lenses appear distorted is often because the distance from which we view the resulting image is at odds with the perspective in the image itself. If you view the image from closer than the normal viewing distance, or the finished image is much larger (having the same affect as viewing it from closer), you will see that the perspective looks natural or realistic and the 'distortion' has disappeared. So I don't think the 'distortion' happens when the image is taken rather when it is viewed at the wrong print size/viewing distance. Try it. It's explained much better by Rudolf Kingslake (Director of Optical Design at Eastman Kodak) in 'Lenses in Photography' (1951) where the entire first chapter is called and is about Perspective. It's a superb book and worth reading if you're into that kind of thing (optics, lenses etc) although there are lot's of good books on the subject.

[benwheeler]

Once again, I really appreciate all the time taken here to thoroughly explain different aspects of this issue. I'm a nerd deep (ok not too deep) down, so more than happy for a nerd fest. To respond to a few points and questions:

- Most pieces I've made are stand-alone or otherwise mobile, but the one that got me thinking about alternative photographic solutions is a 3.6x2.6m bookcase that takes up a whole wall of a small-ish room. So there's no moving the camera further back - I'll either have to be satisfied with a pretty wide angle shot, or experiment with stitching.

- Why would one need a macro lens for stitching, as suggested in a previous post?


And as a bit of a tangent.. Has anyone come across the Wanderlust Travelwide, a Kickstarter 4x5 camera? Looks interesting. Anyway, I'm still interested in having a crack at either MF or LF at some point, but my immediate need for it seems to have died away thanks to some forceful wisdom

[arthurking83]

It should be noted that at a deep down nerd level, the premise that a longer focal length lens will have less distortion than a wider focal length lens will.
There are different types of distortion to comment upon here too.
The main distortion effect we all see in wide angles is geometric distortion, usually seen as barrel, but then as you zoom in with a wide zoom lens it then turns into pincushion type.

Perspective distortion comes in various types as well, you can get the typically seen tilted perspective distortion or vertigo look known as convergence and divergence, where parallel lines converge/diverge depending on the amount of tilt in the camera lens setup. This is easy to correct for with careful setup and can also be digitally corrected for too.
But there's also compression/extension .. and this is where the focal length of the lens plays the largest role in lens distortion .. and can't be accounted for or corrected for in any way.
Compression/extension is a property of the lens's focal length, and hence magnification.

For all distortions other than compression/extension distortion, they can be minimised or eliminated with good practise, and or a solid workflow.
The only distortion that is solely dependent on lens focal length(and therefore format size for the same FOV and framing) is compression/extension.
But at the focal lengths the OP is commenting on, the hassle(of using MF) isn't worth any real benefit.
That is, the perspective distortion with respect to compression effects of a 50mm lens compared to a 35mm lens is minimal at best .. and almost certain to be unnoticeable to just about any and every one.(hence the comment above re the hassle of using MF instead of the 135format that you already have)

YES! there is a distortion difference in a nerdy technical sense, but no you won't really see it.
The compression effect is really only noticeable between focal lengths of great difference(ie. 20mm vs 85-100mm or whatever).

I once did the test(coz I'm also a deep down nerd at heart), where I shot a stitch panorama series of images at about 10-15mm on a UWA lens(about 20 or so images in total .. eg. 4 across and 4 down) and then shot a 200mm-ish reference image to compare.
Image was ugly as it didn't encompass any thought for composition, other than to frame an infinity focal point between two leaning trees at the edge of the frame.
The focal point was infinity and I stood right up in line with the two edge trees and shot (basically) a 180° pano all round with the UWA, and then stood back about 20m or so and the same shot with the telezoom lens(roughly speaking at about 200mm .. maybe 150mm, can't remember exactly).
The difference in actual rendering was stark!
The tele image had the so called background much closer relative to the two trees in the foreground(compression). But the background looked like the main subject in that image.
By comparison(when the images were scaled to the same output size), the pano shot with the UWA lens you could barely make out any detail in the background if you wanted to see the trees(extension), but could 'zoom in' to the same detail level in the background if viewed at 100% pixel zoom level.

Where compression/extension is usually taken into consideration is in portraiture where a longer focal length is usually recommended as a complimentary rendering of the subject.
Nothing to stop you from shooting a portrait at 35mm but the facial distortion will be noticeable if you 'look closely' .. where the nose may appear to be bigger than reality.
Same framing with a 135mm or longer focal length and by comparison the nose will look normal. All this is simply due to compression distortion(which also takes into consideration of extension distortion that an wide angle lens will create). Hence why a portrait lens is usually something like 85mm on a 135 format .. and why larger formats mediums are generally used for portraiture .. longer lens for a FOV.

.....

- Why would one need a macro lens for stitching, as suggested in a previous post?

.....

Macro lenses usually produce more clinically accurate images, with fewer aberrations(distortion/CA/field flatness/etc).
No real need for it, and you could easily achieve the same effect with any regular lens of the same focal length .. but a macro lens of repute will give you just a very slight edge in the total rendered image's quality. Flatter field and less geometric distortion from the macro lens should allow you more leeway if you do go down the stitching path.

Here's a wiki type link to a visual representation of perspective distortion

scroll down to the images of the water bottles.
Note how as focal lengths become closer in ratio terms, the effect of compression/extension is less obvious and problematic.

[Dug]

And as a bit of a tangent.. Has anyone come across the Wanderlust Travelwide, a Kickstarter 4x5 camera? Looks interesting. Anyway, I'm still interested in having a crack at either MF or LF at some point, but my immediate need for it seems to have died away thanks to some forceful wisdom

I have seen the Wanderlust Travelwide promotions before.
For me if I was to go to all the effort of loading sheet film for a large format camera I would want to have all the movements of a bellows camera.
The Wanderlust Travelwide is a sort of large format Box Brownie with a nice lens.
The image quality would have all the advantages of the format size, but miss out on what sets the large format experience apart from fixed focal plane cameras.