Perspective correction

[GDB]

Hi everybody !

I am new to this most interesting forum, and I am now enjoying the discovery of my new Hasselblad H1D II and the 21mm f/4... It takes time !

I would like to gather explanations and opinions from more experimented photographers than I am about perspective correction.

When I was young and using Nikon gear, I once possessed the 35mm PC-NIKKOR, a quite new type of lens at that time (ca 1972). Then came the digital photography, and many other PC lenses, including the Hasselblad HTS system and perspective correction in RAW processing softwares.

So what are the differences in perspective corrections, or more precisely of correction of architecture photography between
- large format tilt and shift cameras like Linhof, Alpa or others
- Perspective correction lenses
- and post-processing in Phocus, Capture One, DxO and other through keystone correction ?

Let's consider shooting a cathedral like Notre-Dame de Paris, which is interesting because the mais shape of the building is rectangular although both towers are not quite symmetrical, the northern tower being a little wider than the southern. The "Rosace" in the middle is strictly circular.

I have no experience of large format tilt and shift results, and I never took a picture of this cathedral with the PC-Nikkor. But when I shoot the cathedral with a wide angle, and post-process it on the computer, I can correct the perspective of the towers with the keystone command, but the Rosace is no longer strictly circular. So you must use a slider called "aspect" to try to correct this default. But (to me) it is not a true perspective correction.

In other words, what is the solution to shoot this cathedral as if I used a tripod high enough, or some kind of elevator (LOL) to reach the level of the center of the Rosace and shoot from this point ?

Your comments shall be very greatly appreciated

Gérard

[brian]

Welcome Gerard to the Forum

I see you are using the X1D-II. I have been looking for a PC solution for this camera other than the adapter plus the HTS 1.5 converter that makes it an unwieldy setup. I myself have been looking for a compact PC adapter to use on the X1D and I am looking for someone who has tried the Canon or Nikon PC lenses on a Techart adapter. Another possible solution is to alter the lens in the HTS 1.5 to work directly on the X1D without any adapter but I have not had any positive response from Hasselblad on this suggestion. To me this would be the ideal solution in terms of weight, size, cost and resolution.

There is no doubt that the best setup for architecture is a large format or a medium format version using a H-100 or Phase One digital back - but it's a whole lot of camera equipment to lug around and it's not cheap. I have a setup that works well - a Sinar technical camera using a HD6-100 back and Rodenstock lenses and it's actually for sale now here: https://peartreephoto.com/      - go to Pre-Owned equipment and you will see the camera and lenses for sale there - end of AD!

PC lenses do work well, including the HTS 1.5 Converter on a HD6-100 that has full shift-tilt capability. The one drawback is the effective 1.5 reduction factor in the angle of view that makes a 24 mm a 36 mm lens, for example. Using dedicated PC lenses on Canon and Nikon cameras can expand the field of view to 17mm and 19mm respectively but the resolution is not comparable with the larger 100mp medium format sensors.

Using a X1-D 21mm lens can give you a fairly large field of view that permits adjusting perspective in post processing. Also the 50 MP sensor is a benefit when you start stretching pixels to control perspective and distortion - there are limits to what you can achieve. However you need to use Photoshop, rather than Phocus, to gain greater control over perspective and distortion. It's not as easy as merely straightening verticals - the proportions also have to be adjusted to maintain the correct scale of the building [or to get the Rosace round].

In the end you will need to consider your own needs: cost, portability, vertical scale of buildings, resolution, etc..