Tip 8: Olympus Lenses on your Canon SLR

One of the wonderful things about the design of the Canon SLR (both digital and film), is that it is well suited to the use of non-canon lenses via an adapter.

This is possible because of the shorter “flange-2-sensor” distance (eg the distance between the lens mount and the film/sensor) used by Canon. This shorter distance means that lenses from other manufacturers want to sit further out from the lens mount and this allows space for the use of an adapter plate.

I will use Olympus as an example here because that’s my main “alternate” lens of choice. Canon’s flange-2-sensor distance is 44mm, while Olympus’ OM (that’s their Old 35mm film camera/lens range) is 46mm. So the Olympus OM lens needs to sit 2mm further forward from the Canon SLR’s lens mount.

Quite simply then, the Olympus OM-2-Canon EF adapter needs to be “EXACTLY” 2mm thick. I say exactly because if it’s not right, it will effect the lens’ ability to focus at infinity. Other focus distances won't be effected, because adapter thickness variations are easily compensated for in the focusing of the lens itself. But the all important ability to focus at infinity, is good reason to be picky when choosing an adapter.

Another reason why the Canon EF lens mount is suited to the use of other manufacturer's lenses, is that it is “big bore”. Put simply, EF lenses are fatter than most and like the shorter flange distance, this allows room for an adapter.

Here you can see the HUGE rear element of the Olympus 50/1.2, fitting snugly inside the Canon sized lens mount. Note the pin extending in from the right of the adapter. This pin contacts the aperture mechanism of the lens and forces the lens to "stop down" as the aperture ring is turned.

Adapters are available for a wide range of alternate lenses, but I personally use Olympus, Nikon and M42 lenses on my Canon DSLR. As I stated earlier though, my alternate lens of choice is Olympus OM and I tend to use the other mounts only when photographing with friends and borrowing their lenses.

Why Olympus Lenses?

Because they ROCK! Many Olympus OM lenses have long enjoyed a reputation of being high quality, great resolvers of detail, compact, reasonably priced and lacking of (or at least well controlling) optical defects such as chromatic aberration and distortion.

Naturally there are some dogs in among the OM lens line up, but name me a manufacturer who doesn’t have the odd dud design….. and don’t say Zeiss, even they have a few!

My first venture into OlyOnEOS was with the Olympus 21mm/f3.5. This lens is one that had received rave reviews for quite some time, but sadly, after 3 versions I was yet to find a good one... soft corners and chromatic aberation were a very real problem. The f2 version of this lens commands big $$$ and perhaps it is better than the f3.5, but my experience with the f3.5 put me off taking the dollar risk and purchasing an f2.

So presently my Olympus lens line up includes a 24mm, 28mm, 35mm and a 50mm/1.2. The later being one of my faves, as the 1.2 aperture allows minimal DOF images at a regular field of view.

As you can see in this headstone image, the DOF from the 50/1.2 is shallow and maintains focus only on the flowers, while the background quickly becomes soft.

It should be noted that these flowers are actually sitting right beside/on the headstone.... there is no space helping with the background separation. An image like this would not be possible with a standard 50mm, as it's smaller aperture would always maintain some background focus.

The 24mm is an amazing sharp lens that resolves incredible detail…. This I use mainly for panoramas, as the 24mm field of view (in the vertical orientation) and minimal curvilinear distortion (if any) produced by this lens is perfect for stitched landscapes.

This billabong image is the result of 15 vertical images, stitched to form one 140Mb file that is almost 3 feet wide... and that is "before" any interpolation to increase size. This image could easily be interpolated to 6 feet wide or more, while still maintaining extremely good quality.... this is why lens resolution or "resolving power" is so important.

This image will give you some idea of the resolving power of the Olympus 24mm.

It has been cropped out of the above Billabong panorama and is presented here at 100% of it's original size. By that, I mean that if you were viewing this image on the wall, this tiny portion of the image would be the size as seen here.

The 28mm and 35mm are equally impressive as the 24mm in all respects and get a run when the longer focal lengths are required, but I will admit that it’s normally the 24mm that I grab for this type of image.

I have owned longer focal lengths too and like my lenses listed above, they were very good performers. I did not keep any though, as my Canon long lenses are extremely good and I have no reason not to use them.

Here is a direct comparison between an Olympus 75-150 and Canon's famed 70-200/f2.8 (it's too big for the blog)

http://www.potd.com.au/samples/oly75-150/Oly-CanonTest.jpg

...as you can see from the linked image, the Olympus is quite the performer and takes it to the Canon quite well, matching detail and sharpness, although it's slightly underdone on contrast. (This is easily fixed in Photoshop however)

What about AF?

Naturally manual focus lenses don’t magically become auto focus lenses when plugged into an auto focus camera, so a bit “old school” technique must be employed. (I will guess that at least some of the people reading this have never used a manual focus camera before…… geez I feel old!)

Manual focusing takes practice and often, best results are achieved using the “focus though” method. This is where the focus ring is turned past the point of focus to where the image is soft again. At this point the focus ring is turned in the reverse direction, again past the point of focus to a point where the image once again appears soft.

This is repeated two or three times, decreasing the amount of "focus through", until the photographer can easily recognise the actual point of focus. With practice, this method becomes second nature, fast and quite accurate.

Having said that, the most common DSLRs now use an image capture area smaller than that of the older 35mm film SLR cameras. This results in a smaller view finder and this makes manual focusing that much harder.

Luckily some clever lad has come up with a way trick your camera into thinking that the old manual focus lens, is actually a new auto focus lens. This is done by including an AF circuit on the lens adapter…. As far as your camera is concerned, it is wearing an AF lens and the focus confirm light and beep work as normal. What a clever little lad!!

Another option is interchangeable focusing screens. If your camera offers this feature, you can install a “split screen” that will aid with manual focusing. These screens have a centre circle that is split in two and when the two halves line up, the image is focused. (I personally use a split screen)

OK that’s focus, but what about exposure and stopping the lens down?

Well the camera can’t stop the lens down, it just doesn’t have the mechanical connection needed, so this must be done manually by turning the lens’ aperture ring. As the aperture closes, the image within the viewfinder will darken, so it is best to focus first, then stop down. (You won’t be shooting much sport with these lenses)

Your camera will set the exposure based on the stopped down lens and if using Av (aperture priority) it will do so automagically. If using M (manual) it is a simple matter of setting the correct shutter speed for the aperture using your camera's viewfinder exposure meter or a handheld meter. (It should be noted that Tv (Shutter Speed Priority) cannot be used, due to the camera not having control of the aperture as previously mentioned.)

Is it worth the effort? Stopping lenses down, putting up with dark viewfinders, having to focus the lens manually…..?

Heck yes! If you are like me, you crave the best image quality that is possible. The extra resolution that a good lens produces will take an image to a new level. You may not notice this at smaller print sizes, but start doing big enlargements and you will easily see the difference that a good lens makes.

So where do I get an adapter?

(Please note update below)

Ebay is the best place to start as there are always heaps advertised, but be willing to do some homework before you jump in. There are plenty of cheap ones out there at least some of them are not worth the risk. Remember, we are dealing with optics here and the machining involved must be precise.

Many adapters are produced by hand and this means that variation in thickness is not uncommon. I purchased one of the cheaper adapters in the beginning, but soon found that I could not infinity focus thanks to an inaccurate adapter thickness.

Adapter accuracy becomes even more important when zoom or internal focusing lenses are used, as Kennedy McEwen pointed out in a news group recently....

"If you are using a zoom lens then the wrong adapter thickness, whether too thick or too thin, will result in the focus drifting with zoom. So you might get excellent manual focus at the long end of the zoom and find the focus shifting when you pull back to the wide end of the zoom.

All of my OM lenses have separate zoom and focus rings and hold their focus excellently throughout the range. This seems to be typical of older MF lenses, while AF lenses which can rely on the electronics correcting any mis-focus as soon as the shutter is pressed, and it is a shame to lose that reliability because of a cheap adapter.

Also, lenses which use internal focussing mechanisms (rather than shifting the entire optical assembly back and forth) rely on the correct backworking distance for optimum performance. A poor adapter can result in sub-optimal lens performance, with resolution much lower than it should be." Kennedy McEwen.

So when you find an adapter on eBay, be sure to ask the seller questions about the accuracy of it's build and also their return policy.

I have since moved to a much more expensive Kindai adapter (AUD200+) and it is machined beautifully. Coming from a CNC machine rather than a set of hands, guarantees accurate thickness and ZERO variation.

Kindai don't offer AF module adapters however, but I am quite happy with my slit-screen focusing for now.

So that's a bit about using Olympus lenses on your Canon SLR. If you have any specific questions, please feel free to ask them in the comments area.

Also see: http://russellspixelpix.blogspot.com/2007/11/focus-confirm-adapters-vs-split-screen.html


Cheers

Russell
AustralianLight Landscape Photography: http://www.australianlight.com.au


Update - March 2011: After having another look at today's available adapters, I would suggest that the Fotodiox Pro range is definitely worth considering. As well as the adapter shown here, Amazon also offers budget and AF confirm versions....



Tags: olympus om lens canon eos adapter zuiko lenses canon body dslr slr focus confirm chip alternate lenses

Rusty's Ramble #4: "If you build it, he will come"

"If you build it, he will come" (it's a line from a Kevin Costner movie) or in photo speak... "If you wait, the image will come".

Just a quick ramble about an image that I shot this afternoon.

I drove up to the Qld Sunshine Coast for some R&R and camping today. 2.5 hours from home and I am dealing with freezing temps, gale force winds and the difficulty of finding something worth photographing.

Shortly before sunset I had just about given up, in fact I had given up, but I forced myself to get the cam out and take at least one pic so that the day wasn't a complete waste.

I looked around were I just happened to be and figured that "I may get a shot down there". So I set up for what was a very ordinary shot in dull light. While doing this the phone rings and my wife is calling me back to camp to pack up and go home.... "it's too cold and sleeping in a tent is just not on!"

So I have a dull and boring shot, I have a freezing wind that is sending brass monkeys looking for welders and I have my lovely wife in my ear saying "let's go".

Then just for a few seconds this happens.... 



...the light broke through the clouds and lit the scene in a way that I had never even hoped for.

So the moral of this very brief ramble?

"Wait it out till the light is gone, because you just never know what will happen."

Sunsets and sunrises change quickly and if you are not ready and waiting, you may miss something special. (I am not saying that this image is anything fantastically special.... it's just something that I was not expecting, that came out of absolutely nothing and then it was gone)


Cheers

Russell
My Gallery: http://www.pixelpix.com.au/gallery
Australian Digital Photo Of The Day: http://www.potd.com.au

Photography help for beginners - Film & Digital Camera Techniques - Post Processing - Photography tips and tricks - Rusty's Ramble

Tip 7: Panoramic photography on the cheap!

I am in process of moving my blog to my AustralianLight Landscape Imagery web site. Please find an updated version of this article at http://www.australianlight.com.au/blog/post/a_beginners_guide_to_shooting_panoramic_images/

The Poor Man's Pano Head

Not being one to shell out the big bucks if I can make it myself... I set out to make a cheap panoramic head that would provide me with nodal point rotation.


First place was eBay looking for a macro focusing rail. I was lucky enough to find an AU seller with an Olympus rail that had been listed only moments before and it had a "Buy Now".... sweet! So 2 mins and $49 later it was mine. (I also noticed that the same seller had a set of extension tubes.... I figured "Heck, I have a macro focus rail... I might as well have some macro as well!! "Another 2 mins and $20 and they too were mine)

I was very pleased when the items arrived, as they were brand spanking new!!! I seriously doubted that these had even been close to a camera! The Olympus rail is extremely solid and well built and I couldn't have been happier with the purchase.

Ok... so I got the rail, next step was to mount the camera in vertical orientation. A quick stop at the local hardware and a $3 bracket (yet to be painted in the pix) was purchased. 2 small holes were drilled... one to mount the camera and the other to mount the bracket to the rail (in a position with the lens over the rail) and bingo!... a Panoramic head for less than AU$55!!!!


On this image I have marked the offset so that you can see how the camera rotates around the lens nodal point. This means that no matter where the camera points during it's rotation, the camera-subject relationship does not change.

Nor does the relationship between objects at different distances change.... so when stripping together everything matches and blends perfectly.

The macro rail is perfect for this application, as it allows fine offset adjustment so that the lens nodal can be found for different focal lengths.

Interesting side note: Thanks to the internal zoom, the nodal point for the 17-40 L does not change throughout it's zoom range. This makes compositional changes very easy once the head is set at the nodal.

I have plans for a second bracket that will hold a flash above the nodal. This flash will be used with my "tracing paper" diffuser (more on that in another blog later) in the vertical position and allow for smooth internal exposures without multiple shadows.

What’s this “nodal” thing again?

Your camera lens projects a reverse image…. while cleaning your lenses, you may have seen that the image through the lens is upside down and back-to-front.

No, you haven’t seen this? OK then, try it now…. Remove the lens from your SLR and look through it (sorry compact camera owners with fixed lenses, you don’t get to play this game) and you will see everything is flipped in both the vertical and horizontal directions.

So given that this is the case, we know that the light that enters the front of the lens on the right, exits the lens on the left….. and conversely, the light that enters on the left, exits on the right. From this we can rightly assume that at some “point” within the lens, the light “crossed”.

This point is the “nodal point” or effectively the “optical centre” of the lens (not the physical center… measuring the outside of the lens and dividing it in half is meaningless…. unless you want to know how long half your lens is).

So why is this important to us photographically?

Imagine yourself sitting on the outside row of a merry-go-round. (not the gold horsie… that one’s mine, you can have the silver one) Look out from your position to a friend who is standing still and watching (They are thinking… “How embarrassing is this!! A 43 year old goose riding a merry-go-round…. Sheesh!”)

Your friend has just won a stuffed animal and is hiding it behind their back (you are now thinking…. “How embarrassing is this!! A 43 year old goose winning stuffed animals…. Sheesh!”)

As the merry-go-round rotates, your position in relation to your friend changes…. As your position changes you get to sneak a look behind your friends back and see that it’s an elephant (….bugger! You wanted the giraffe!).

Now change positions on the merry-go-round and imagine that you are standing in the dead centre. As the merry-go-round rotates your position in relation to your friend does not change. At no time are you placed in a better position to see what your friend is hiding behind their back.

This is what is important to us as photographers…. We can rotate the camera taking multiple images and each image will overlap with the previous, because at no time will the camera see anything that is hiding behind some thing else, it will effectively take one big photo over multiple frames. (More important, is the fact that the disappointment of getting an elephant and not a giraffe is postponed for a little while longer) ;-)

Let's look again at the 2nd image above... Here you can see that the camera does NOT rotate around it's own base, instead it rotates around a point located within the lens and above tripod centre .... this is the lens nodal.

This diagram shows how nodal rotation does not effect the relationship between objects.

Nodal rotation allows for easy stitching of images because (and to put it quite simply), everything lines up no matter where you point the camera.











The following diagram shows how objects appear to move in relationship to each other, when a camera is rotated around a point other than the nodal. (eg the camera base mount)

This presents impossible challenges for stitching, as no two areas that you are trying to blend will be the same. This can be overcome ONLY with physical intervention on the image in post process and when you may have as many as 15 images to blend, do you really have the time?

Nodal rotation is much easier and no matter what you paid for your pano head, it will seem cheap in the long run with the time that you will save!!




At this point, I will take a moment to mention that hand-held panoramas are possible, but these are best kept for compositions with distant subjects only.


So how do we determine the nodal?

There are a number of databases available on-line that will let you know the offset required.... these are great for fixed focal lengths, but are of little use when you are using a zoom, because each time you position the zoom, can you really be sure of the exact focal length that you have selected??

From my experience with this, I have found that setting the nodal by eye is very effective and accurate. To do this, pick 2 objects at different distances (larger distances are better) and position them in the right of frame. Note the relationship between these objects (eg are they aligned, one just touches the other etc).

Now rotate the camera and position the same objects in the left of frame. Again note their relationship, has it changed?? If it has changed you have not rotated around the lens nodal. Adjust the offset distance and repeat the test.

After a little bit of tweaking you will find the nodal and see that left frame/right frame views of your objects do not change. Now you are ready to take some panos!

Tripod setup: Yes you MUST use a tripod if nodal rotation is required, as this relies TOTALLY on the fact that there is a fixed point of rotation. You cannot hand hold and rotate around a nodal, it is simply not possible.

Make sure that your tripod has a firm footing on the ground. Using a level (some tripods have levels built in) and the tripod's adjustable legs, make sure that the base plate of your tripod head is level in all directions.

Still using the level, make sure that your tripod's top plate (where the camera normally sits) is also level in all directions. Now carefully place your camera/pano head and secure it well.

Oh... I should mention, it is really nice to use a solid stable tripod. A camera, lens and pano head can be quite a load with the offsets involved and fiddly little tripods are not recommended.


Landscape or Portrait? Well you can shoot in both, but I feel that portrait orientation is best. Why? ...I am glad you asked. When you think about it, a panorama gives you the ultimate wide angle lens. In fact every lens in your kit becomes a wide angle that is capable of a full 360 degrees (you can keep going round and round if you wish), so why not maximise your vertical FOV (field of view) by turning your camera into the portrait position.

Image overlap: When taking images make sure that each image overlaps the last be at least 1/3 (1/2 is better) as this will give your panorama software (I use PTGui) plenty of room to find points of alignment and plenty of room for your blending software (I use SmartBlend within PTGui) to make smooth, invisible transitions.

Exposure: You will need to fix your exposure from the start, so that it remains constant for ALL shots. If you allow your exposure to vary you will not get smooth transitions across your panorama image. Here I recommend shooting in manual mode and setting the exposure to just maintain detail in the brightest part of the image.

Large rotations can provide great variation in exposure and I think it best to maintain highlight detail and pull detail out of the shadows later if required. (Remember, if you blow the hightlights there is nothing left to recover in post.... blown is blown!)

Focus: I have found that using a common focus for all images works well. Stopping down your lens for lots of DOF will keep both near and far objects acceptably sharp with this technique, but depending on the effect you are after, you can elect to have shallow DOF or selective focus just as you would in a normal single frame shot.

If your subject distance varies greatly with the rotation, you can even focus with each frame and allow the focus differences to blend from frame to frame. Experiment with this and see what works for you. Sometimes this technique is successful, sometimes not.... it depends on the variation in the subject distance.

Focal length: Panoramas can be made from any focal length provided that your lens does not provide uncorrectable curvilinear distortion. (eg super wide angle or fisheye lenses)

So pick your focal length to suit your subject. In this image I am only interested the distant view and the close foreground is not important. So I have used a longer focal length of 112mm (70mm on 20D). If I had used a wide angle lens the more distant objects would have been quite small....

View this image large: http://www.potd.com.au/gallery/albums/userpics/10002/ABigWideLand.jpg

In this image I wanted more foreground and sky, so a wider focal length was used...

View this image large: http://www.potd.com.au/gallery/albums/userpics/10002/HighOnAHill_Stitch.jpg

So that's the images... now how to stitch them?? Well there are a number of applications that are available to do this and I will let you find one that floats your boat, but I will recommend PTGui and the Smartblend plugin http://www.ptgui.com/ as I have found the results nothing but excellent!!

I should also mention that it is wise to overshoot your panorama by 2 or 3 frames each end. When being stitched the individual images are "warped" to fit together, the is means the final result tapers at each end.

This is not a problem if you don't mind cropping some off top and bottom, but when you are a megapixel monster like me, you want every bit of image data that can be salvaged. So over shooting moves the taper out to unwanted sections of the image, these can then be cropped off the end without effecting image height.

One last thought..... Don't be afraid to try different subjects. Many panoramas are of landscapes and the pano format is perfectly suited for this, but panos can also be fun even in tight situations....

It's up to your imagination where you think you could use the panorama view.

These and some of my other panoramas can be viewed at my gallery link below. When in the gallery, please search "pano".

Cheers

Rusty
AustralianLight - Landscape Photography


UPDATE: Panoramic photography on the cheap! - PART 2 is now online.


Tags: panorama panoramic pano landscape image photo photography wide format 16x9 617