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Tilt and shift... questions

Sid Jervis

pro member
Can anyone give me a reasonable explanation of why all three TSE lenses are the same price, yet only one is an "L" ?

Also, I understand the 24mm in meant to produce softer images than the 45 or 90. Is this rumor, urban myth or fact?

If you had the $$ to buy all three, but only at the rate of one per year, what order would you buy them?

Cheers
 

Alain Briot

pro member
Yes, the 24 is the softer of all three. As to the buying order, what Kind of photography do you intend to do with these lenses? That's the deciding factor!
 

Stan Jirman

New member
The "L" in itself doesn't designate a particular quality, rathe than it has a UD glass element (that's Canon's own definition, last time I checked).

The 24 is relatively soft, but the image is very even; that can't be said for many other lenses. The other two are sharper and also very even, the lack of "L" simply means that they don't have an UD glass element.

The order depends wholly on what you want to shoot; for me, it would be 24 and 45, and no 90; I shoot landscapes and the occasional architecture. If you want to shoot people or macro, the 90 is more suitable and the 24 less. It all depends :)
 

Sid Jervis

pro member
Alain Briot said:
Yes, the 24 is the softer of all three. As to the buying order, what Kind of photography do you intend to do with these lenses? That's the deciding factor!
Apologies - nice to have a reference point.
Subjects, landscapes and architecture.
 

David Bostock

New member
For Landscape and Architecture, I would recommend the 24 followed by the 45 as Stan suggested. The 24 is softer than the other two, but all three are wonderful lenses for what you want to shoot. Good luck with the buying decision.

Cheers,
 

Alain Briot

pro member
Are you planning to shift-stitch or use "as is" full frame? For shift-stitch the focal length is halved meaning a 24 becomes a 12mm, a 45 a 24 and a 90 a 45... Nice since all 3 focal lengths are half of the next one but something to keep in mind.
 

Sid Jervis

pro member
Alain Briot said:
Are you planning to shift-stitch or use "as is" full frame? For shift-stitch the focal length is halved meaning a 24 becomes a 12mm, a 45 a 24 and a 90 a 45... Nice since all 3 focal lengths are half of the next one but something to keep in mind.
OK - please point me where I can understand the logic of this, or tell me.
Do you mean shift stitching gives a FOV that is the same as a lens with half the focal length?
 

Asher Kelman

OPF Owner/Editor-in-Chief
Sid,

It's simple.

The 45mm lens can capture light from a wide angle of landscape. Actually anything that is within 25 degrees to each side of a point directly ahead.

The width of landscape is normally limited by that total 50 degrees of capture of that lens.

So, how to increase the width of landscape seen by the 45mm lens?

O.K. we could step back, but there's a road!

Another way is to use a lens with a wider angle of capture, for example a 24 mm lens. Here the angle is 84 degrees. A lot better. However, all this extra information has to be recorded on your one small CMOS chip!

So, if there is a lot of detail in the landscape, that information can't all fit into the single little chip! (Why? lens and pixel limitations).

So, details of a flower or a single leaf are going to be short-changed. How can we alter that? The camera, after all, only has one single sensor!

Now, if we have a 45mm shift lens with the same capture angle of just 51 degees, we can get a wider piece of landscape by making it work as if it had several sensors alligned sided by side, each capturing an adjacent section of the scene.

It works this way. The lens is larger than usual and produces an image circle with the [COLOR=BLUE[whole[/COLOR] landscape focused on the plane which contains, at its center, the single camera sensor.

In fact, much of your great landscape image is shining to either side of the single CMOS/CCD sensor.

Now, here's where the shift comes in. If the lens is shifted to one side, the part of the image to each side can now be made to land on the sensor.

So three images can be taken; one central, one shifting the barrel of the lens to the left and one shifting the barrel of the lens to the right.

(for the advanced user, to prevent errors of parallax, the camera needs to be shifted, not the lens!

We "achieve" this by counter-shifting the camera on the tripod by the same number of mm that the lens was shifted, but in the opposite direction. We'll explain that more fully in a later article.)


When these 3 images are taken (with care to use the same light meter settings since we switched to manual!), they can be imported into photoshop, dropped into a wide empty "New" image frame as three layers.

The overlapping parts are alligned and the image can be flatenned.

Without going into details, by not using straight join lines, one can completely hide any trace that the image was derived from 3.

Now, if you would compare this "panoramic" image with that produced by an ordinary 24mm lens, you would find that there is much more detail although the width of landscape covered is similar.

So this is how a lens' "focal length coverage" can correspond to a lens of about half that particular focal length. In this case from 45mm to 24mm.

This effort allows one to essentialy "double" the MP of your camera for landscape! You get the same image, but it can be enlarged more aggressively for perfect prints.

Asher
 

Alan T. Price

New member
#1 the 90mm for it's pseudo-macro capability plus it shows the tilt effect more obviously.

#2 the 24mm for its wide angle coverage (although how wide depends on the body you use - hardly at all on a 20D). The massive DOF of 24mm tends to disguise the tilt effect.

#3 the 45mm. It's neither wide nor telephoto nor can it focus close-up like the 90, but it has its uses.
 

Sid Jervis

pro member
Alan321 said:
#1 the 90mm for it's pseudo-macro capability plus it shows the tilt effect more obviously.

#2 the 24mm for its wide angle coverage (although how wide depends on the body you use - hardly at all on a 20D). The massive DOF of 24mm tends to disguise the tilt effect.

#3 the 45mm. It's neither wide nor telephoto nor can it focus close-up like the 90, but it has its uses.
Thanks, you (and others) have confirmed that the 24mm TSE is the one I will purchase.
 

Ellis Vener

New member
Sid Jervis said:
Can anyone give me a reasonable explanation of why all three TSE lenses are the same price, yet only one is an "L" ?

Also, I understand the 24mm in meant to produce softer images than the 45 or 90. Is this rumor, urban myth or fact?

If you had the $$ to buy all three, but only at the rate of one per year, what order would you buy them?

Cheers
while the EF 24mm T/S may be "softer" than the others , I tend to doubt that Canon did that deliberately.

With the EF 24mm lens, because of the inherent larger depth of field for a given f-stop, lens shift is going to be more useful than tilt for most general subjects especially when yo uconsiderthat you are more likely to use the lens at f/5.6 to f/11 for both depth of field (visual perception) and a higher level of resolution (optical performance). This is especially true wit hcameras liekthe 5d and 1Ds models. for smaller format cameras like the 30D tilt will become somewhat more important as the angle of view will be much narrower o n the smaller format.

For really extended near -far compositions then tilt comes into its own but you'll still need to stop down to keep the mid ground in focus.
 
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