Teleconverters and shift lenses
Extenders/Teleconverters and shift
Using tilt/shift lenses and extenders
Extenders and teleconverter are widely used with longer focus lenses to increase focal length, however they also work with several tilt/shift lenses.
Keith has been looking at how the optical changes when using such devices affect the results using tilt/shift lenses and adapted lenses.
The adapter came from MPB (see ad at the right)
The basic teleconverter is a negative (concave) lens that effectively increases a lens’s focal length when placed between the lens and the camera sensor. This is the same as making the image projected onto the sensor larger. This increase in size, for the same amount of light coming in through the lens reduces its brightness.
This expansion and dimming of the image is seen by the photographer as a longer focal length and reduced aperture. Some time ago I had a Canon 2x extender, which I used occasionally with my EF70-200 F2.8L IS lens.
This gave me an effective 210-400mm f/5.6 lens – the 2x factor dropping two stops of aperture and doubling the focal length. It was the mk2 version of the extender and whilst occasionally useful, didn’t really give the performance I wanted.
The Canon extenders are now at mk3 and are said to be much better in performance from an image quality and distortion point of view. The adapter in the main part of this article is the Canon Extender 1.4x III (obtained used at a fraction of the list price from MPB)
[Click on any image to enlarge]
The adapter doesn’t officially work with Canon TS-E lenses, since they do not have the additional rear electrical connectors found on Canon’s longer lenses.
The extenders do work, but their presence is not noted in image EXIF data. That means my TS-E24mm with the Extender 1.4x gives a working focal length of ~34mm and a stop reduction in aperture. However, the photo EXIF data will show 24mm/f/8 for example, when the photo was really taken at 34mm/f/11.
Note: there is a page of data about all of Canon’s extenders on our EFLens site
The front of the extender reaches forward into the lens EF mount. Note the black rubber weather-sealing ring at the back.
The front extension physically excludes some lenses such as the EF50/1.4 (centre), but not the MP-E65 1-5x macro(right) or TS-E24mm F3.5 L II (left)
The extender works just fine with Canon’s EF->RF adapter, although a range of RF adapter/extenders may well appear before too long, given Canon’s desire to move to RF mount.
The TS-E17mm F4L seen above was tested a few years ago with my 2x extender and Canon 1Ds mk3 camera.
Whilst it worked, the results were not good enough for the 2x to become a feature in my kit bag.
The medium format adapted lens
Since the 1.4x extender on the TS-E24mm F3.5L II gives around 34mm, I also did some quick comparisons with the Mamiya Sekor C 35mm/3.5 M645 medium format lens and Fotodiox adapter I recently tested on my EOS RP. This gives ±15mm of shift and 10º of tilt [Detailed Fotodiox TLT ROKR review]
It so happens that in my collection of assorted ‘stuff’ I’ve a teleconverter for M645 lenses. The ‘2X M45 Teleplus MC6’ is a 2x extender, so probably not one I’m likely to use with the 35/55/80/210mm M645 lenses, but I might give it a go on the 210 to see what tilt looks like on a 420mm f/8 lens…
I’ll come back to this one later, when looking at shift vignetting.
Using the 1.4x extender
I’ll start with examples showing how much vertical shift is available. Due to the expansion of the image circle, the equivalent shift is also increased. So, the ±12mm of shift at 24mm becomes ±17mm of shift for 35mm when the 1.4x extender is in place.
The photos here are stitched pairs, showing two shots at full vertical shift (rise) and none. I’ve drawn boxes on the images to make the shift effect more obvious. If you’re unsure of how this works, have a look at my article about using shift – How to use lens shift
Two views at 24mm and ~34mm
There is a bit of mismatch in the up/down shift of the second one below – I’ll put this down to it being a very windy day and my swapping lenses However it did make it easier for me to draw the rectangles…
Now a version with the Mamiya 35mm/3.5 lens on the EOS RP using the Fotodiox adapter.
It is a fractionally longer focal length, so gives a tighter view of the building (the tripod wasn’t moved) but notice the difference in relative shift between the 35mm and extended 24mm.
Using the 1.4x extender on the TS-E17mm gives an effective focal length of ~24mm.
Here’s a similar comparison stitched shot between 17mm+1.4x and 24mm
This is the same photo as shown earlier – just the TS-E24mm F3.5L II lens
Three single shots taken with the 24mm, 24mm+1.4x and 35mm from the same spot.
Of course, I could have moved backwards/forwards to get the framing I want, but the three shots show how at the same camera position it’s only the crop/FOV that changes with changes with focal length. If you printed each at three foot by two foot and viewed the prints on a wall from the same distance, then yes, the perception of depth would change, but that’s a whole different matter…
When I tested the TS-E17 with the Canon 2x extender mk2 I decided that, yes, you could use it, but that the increases in distortion and loss of sharpness were too much for my liking. Two stops increase also pushed the f/8-f/11 I like to use with the TS-E17 to f/16-f/22 which is starting to show softness from the small aperture (more noticeable on my current 50MP 5Ds than the 21MP 1Ds mk3 I had in 2009).
I’ve not got the patience (or kit, but mainly patience) to do proper resolution tests. but the building you can see above has some nice fine detail that lets me decide if I feel a lens combination is usable for my work.
A photo, with the camera tilted up (24mm +1.4x)
Why tilted up? – I was also taking photos for a look at using some updated software to correct converging verticals.
Anyway, the shot is at f/5.6, which becomes f/8 with the 1.4x extender. The TS-E24 works well at f/5.6 even though if I’m using a lot of shift I’ll up that to f/8-10.
Here’s a view of the top corner zoomed to 200% [click to enlarge]. It’s followed by a version after applying Topaz Sharpen AI [review] – my current best choice for sharpening shifted images, since it doesn’t assume any symmetry for the distortions in the image.
A similar comparison for the TS-E17mm and 1.4x also at f/5.6 (f/8 with extender)
I also tend to use the TS-E17 at ~f/10 if I’m going to be shifting much and need corner detail
The TS-E24 showed no significant geometric distortion whilst the TS-E17 showed a very small amount of barrel distortion – something that I’ve occasionally noticed when doing 4 way diagonal stitching with the (unextended) lens in a TSE Frame. It’s slight and wouldn’t be an issue in many shots.
I can’t truly compare the TS-E24+1.4x with the Mamiya 35mm lens since one was on a 50MP 5Ds and one on a 26MP EOS RP, but the TS-E seems to give better contrast and less chromatic aberration. Given that I consider the (1980’s) Mamiya lens good enough for some paying work, the 5Ds/TS-E24+1.4x is definitely a combination for my work.
The TS-E17 and extender is good, but obviously not up to the standards of the unextended TS-E24. If I could only get the one TS-E lens, then a few hundred quid on a used 1.4x mk3 converter would be fine, since I tend to use the TS-E17 rather more than the TS-E24.
The Hasselblad HTS extender
A while ago I tested the HTS1.5 tilt shift unit with an H6D-50C camera. The adapter is a combined 1.5x extender and tilt/shift adapter for the Hasselblad H6D system.
Have a read of the article for more observations and examples, but the combination of XCD28mm lens, HTS adapter and (small) medium format sensor gives a focal length roughly equivalent to ~33mm on a 35mm sensor.
Two images, one with the H6D and one stitched with two TS-E24mm + 1.4x shots.
From a detail point of view I’d have to give it to the TS-E24+1.4x rather than the XCD28mm+HTS1.5. Apply Sharpen AI and the images are much closer. I should say that this doesn’t look at any advantages the medium format sensor might have in colour handling and dynamic range – I’m just looking at detail.
My suspicion is that this reflects better optics (when shifted with an extender) in the Canon than the Hasselblad setup, but I’d be happy with either for commercial work.
A note on vignetting
When doing the testing for some of my Canon TS-E lens reviews I looked at how the physical lens construction caused some additional vignetting at full shift at wider apertures. This is on the opposite side to normal lens vignetting. This is from my TS-E24mm F3.5L II review where I’ve taken photos of a flat light source and darkened/posterised the images to show the vignetting more clearly.
The physical vignetting caused by the mount is easily noticed from the rear of the lens (shown not stopped down at all)
I was curious as to how this changed with an extender in place.
Here’s a set of images at 0/6/12mm of shift
I was expecting the shift vignetting to be reduced, but I wasn’t expecting a new form of vignetting to appear at small apertures (f/16 and f/22). Not that I use f/16 and f/22 very often and these apertures are the ‘pre-extender’ or set values – add a stop for effective aperture.
Just for completeness here are the shift vignetting examples for the Mamiya 35mm and 35mm+2x on the EOS RP.
The first example confirms my thoughts that the RF mount and adapter are causing no vignetting issues, whilst the extender seems to be showing a slight ‘squaring off’ of the vignetting pattern.
I suspect any non circularity comes from the aperture stop in the adapter or the one at the back of the 2x converter.
Either way, I’ve just included it for completeness sake…
Any extenders degrade image quality by some amount – what’s acceptable depends on your photographic needs and budget.
The older Canon adapters are OK at a push, but introduce too much distortion and image softening for my liking.
2x converters have more effect on image quality than 1.4x ones
Modern sharpening software can work wonders on lens softness.
The Canon Extender 1.4x III works a treat with the TS-E24mm F3.5L II and quite well with the TS-E17mm F4L
An extended shift lens has more shift. So a 24mm lens with 12mm of shift becomes a ~34mm lens with ~17mm of shift. This can be very useful for shift/stitching if your original lens is of sufficient quality.
If this article has been helpful, I’ve written many more related to using tilt/shift lenses that may be of interest.
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