Thursday, 9 June 2016

Mastering Your Kit Lens - Part 6

A Vertical Panorama, probably equal to around 14mm on APSC.

Your kit lens normally offers 18mm at the wide end but what about when you want super wide angle shots with your kit lens ?  

The answer will have you in stitches.

Most kit lenses have one focal length that is just better than all the others, chances are its somewhere in the 24-30mm range for APSC cameras. If you can work out what this focal length is via testing and determine the optimum aperture, you can press your kitty into service for excellent panoramas...even really big ones, or not perhaps so big ones.

It is true that most panorama applications these days can correct distortion automatically, however it all works better if the files are close to distortion free to start with as distortion corrections reduce details along the sides and in the corners of the image and in any case the corrections are often less than perfect. 

Many cameras are now offering some sort of panorama option, either helping you to line things up in the camera for example Olympus or even stitching the images in camera as with most Sony models. You can pan horizontally or vertically or if using post capture assembling even shoot in a matrix, regardless of which method you apply the resulting image (for non-moving subjects) will probably significantly exceed in quality what you would have otherwise obtained by shooting a single frame on a much wider lens. 

But there is much more to this option, it opens a whole new world of kit lens based possibilities, lets explore. 

The four core advantages with the stitched approach over using a really wide lens are:

Much higher real resolution

Less distortion on the edges 

Greater flexibility for cropping 

Vastly less money tied up in a wide-angle lens that has limited usage for most photographers. 

All of the above factors are quite practical but the stitch also opens up a wealth of creative alternatives that are otherwise difficult or impossible to achieve via normal shooting. 

A Matrix Image, combined from 12 frames, the fine detail resolution in the full resolution image is quite amazing and easily hides the shortcomings of the kit lens, shot with Sony 18-55 OSS at 55mm, distance to subject was about 3 metres, even in this scaled down web version you get the impression that the image is very sharp and detailed.

Really Big Photos 

With the right technique and enough computer processing you can stitch an enormous number of frames together for massive prints or super high res smaller prints (though still big). In theory and practice the more frames you stitch the less important the ultimate resolution capability of your lens becomes as you’re simply never going to enlarge the resulting final stitch enough to see the defects in the donor frames. 

Proper stitching needs careful set-up so most serious panorama shooters work with panorama heads or tools that streamline the process of capturing the frames, however these days the stitching software is so good that you can almost be sloppy with hand held captures and still get great results. 

Anyway, fact is your kit lens is perfectly capable of producing great files for stitching and especially so if you take the time to find the optimum focal length and aperture for your particular lens. Should that focal length be at the longer end of the zoom range it doesn’t matter, you just shoot more pics to cover the required area, if it is towards the wider end you can shoot less frames for the same overall coverage. 

Three Frame Stitch, taken in a lane-way where the 18mm setting was not quite 
wide enough to capture the scene due to the narrow width of the lane.
A sony 18-55mm OSS E mount was used at 27mm for the donor frames.

Three Frame Stitch 

This is rather neat, lets say you need a wide angle shot but your lens is not so great at the widest setting, many aren’t, often they produce odd distortions towards the edges of the frame and lack clarity. 

Well try this, set your zoom to a more moderate wide angle setting , 26-28mm being a good choice for APSC users. Turn your camera sideways for portrait mode capture and shoot three frames to cover the area you need. It’s important you keep the camera level and rotate it as much as possible around the centre of the lens barrel (roughly the nodal point), rather than you spinning on the spot and you need about 20% overlap for each frame. 

Once you open the files and run them through the panorama app on your computer you should end up with an image with about twice the resolution (min) of a single frame and a bit more coverage than the widest setting on your lens with little distortion. If it the final result is distorted you probably chose the wrong stitching option or shot your photo very crooked, practice and experience will make things perfect.  

You can use “transform” tools in your editing program to push and prod the perspective of the resulting image and a fascinating aspect of stitching is you can get perspective renderings that are not possible with a single frame capture. Normally you have enormous control over the "projection" (final perspective look) via the panorama rendering options you choose to apply. 

Another advantage to consider is that 3 - 4 frame stitches normally result in files in the 30-40 megapixel range which gives you a much better array of options for creative editing. Fact is no matter what anyone wants to tell you, more pixels always gives more flexibility in terms of pushing pixels around in post, and that includes: colour, tone, sharpening, contrast and of course post distorting things.

Believe it or not this was taken with a the Sony 18-55mm OSS E Mount set at 18mm, the DOF is very shallow and pleasing. The secret, it is a five frame portrait orientation stitch taken from very close up to the sign at f3. 5

Stitch to Simulate Shallow Depth of Field

Well actually this is not a simulation, you really can get shallow DOF. 

Let me try to explain this. Normally if you used say 35mm focal length on an APSC camera you have to stand back a bit to get all the content in the frame. Now DOF is dependent upon several things, aperture, focal length, the comparative distances between the near and far objects in the scene and overall magnification. 

It’s not the format that matters by the way, there is nothing magic about 35mm Full Frame or Medium format, rather it’s that when you use a larger format the focal length and magnification factors etc have to change to keep things looking the same in the picture. That means that if you actually stitch smaller frames shot with a longer focal length to make one big frame you will probably get a similar look DOF wise to what you would otherwise have obtained shooting in a larger format. 

Think of it like this, you’re using a 35mm lens but instead of standing back to fit the whole scene in the frame you now move in closer to fit only part of it. This increases the magnification factor and the comparative distances between near and far objects in your frame. Hence your DOF becomes much more shallow, even if you used the same aperture. 

Now of course you are going to take a number of frames to cover the whole scene and it quite likely that the resulting image area of the final frame could be as larger or even much larger than a FF camera. 

So what do we get, basically a very similar look to using a much larger format with very high resolution and that shallow DOF many folk crave for potentially at no extra expense, (other than software if we don’t already have it) 

It’s probably worth saying, most people never shoot pans this way, rather they use panoramas to cover wider than normal distant scenes that cannot be done with a single frame. In such cases because everything is relatively distant the DOF will look pretty much the same as it always does for the format you are using. 

I have noticed a rather nice benefit with this approach over regular shallow DOF shots. We often read long-winded discussions on web forums about the quality of the Bokeh (blur effect in the out of focus regions) from various high speed lenses. Very fast lenses often have blur characteristics that are rough and edgy and it is very much dependent on the aperture, anyway my experience is stitched shallow DOF pans have a much more pleasing bokeh that tends to be smooth and natural rather than forced looking. Bear in mind your kit lens mileage may vary but basically it should be similar to the looks shown here as your apertures will be similar to mine and there is a lot more general consistency between kit lens construction than there is with fast lens constructions. 

Anyhow my attached picture will tell the bokeh story better and next time we will explore the macro options a little more deeply.

Again another stitch, this time four frames taken in portrait orientation at 18mm f3.5.
There was quite a bit of geometric transformation applied to the image to square things up. 
But the finished result works a treat and is very sharp where it is intended to be sharp.

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