Upsizing Vs Extender, Which is best?

Recently I purchased a Canon 100-400mm f/4.5-5.6 lens. I wanted to shoot wildlife so getting extra reach was important. Some of the animals I was hoping to capture were either skiddish or dangerous so I didn’t want to get too close. To further increase my reach, or safe distance, I also purchased a 1.4x extender and a 2.0x extender. To add to this equation, I had a Canon 70-200 f/2.8 from before.

I had read and heard that the extenders are garbage and a waste of money, but I really wanted the extra reach 2X would give me so I gave in and purchased the extenders. I felt that they HAD to be better than just ‘upresing’ a photo. I knew that the 2x extender was going to be a slight softer than the 1.4x, but really wanted an 800mm option. I ended up buying both extenders so I could have the 800mm (softer) option or 560mm sharper option and ruled out upresing all together. I also thought that stacking the extenders would be useful in a pinch. Now that I have the gear I am able to do a test that I have been wanting to do for a while and see exactly what type of results I am able to get from this equipment. Even though I purchased the extenders for shooting over 400mm, the comparison is still valid between the lenses. So, if I was wanting to take an image at 400mm with this equipment I have 4 options.

• 100-400mm lens zoomed into 400mm
• 70-200mm lens zoomed into 200mm with the 1.4x extender (280mm) then resized
• 70-200mm lens zoomed into 200mm with 2.0x extender (400mm)
• 70-200mm lens zoomed into 200mm and resized

I don’t claim that my test was scientific or exact but I think it gives me a good idea of how the equipment performs and what I want to drag along on my next trip. Here is what I did… I took a picture of this wicker basket with the 4 lens combinations. I cropped and upresed the images that needed it – bringing them back up to the same resolution as the uncropped images. Resizing was done using Bicubic Smoother in Photoshop CS4 in a single step. The images were taken with a Canon 5D mark II at f/8 on a tripod using a cable release and mirror lockup.

Here are 100% crops taken from the center of the four images.

It is pretty obvious that anything but the 100-400mm lens is fairly poor quality at the 400mm range, with the other three combinations being pretty closely matched. I think the resized 1.4x extender shot is slightly sharper than the resized 200mm shot but it is very close. The 2x extended seems to suffer from some bad purple fringing Next up, 100% crops from the top left corner.

One again our friend purple fringe shows it’s face in the top left of the 2x extender image. The 100-400mm is clearly the sharpest of the bunch. Again, we have a close call between the 70-200 with and without the 1.4x extender.

Update After reading a few test that others had done, and seeing positive results for the 2.0x extender I decided to do another test. This time I used the 100-400mm lens as the standard and put the 1.4x and 2.0x extender on for variations. I was interested in finding which combination gave the best result for a 800mm equivalent. Upsizing the 400mm shot, upsizing the 400mm+1.4x extender shot, or shooting straight at 800mm with the 400mm + 2.0x extender. Here are the results.

400mm f/11 Upsized 100% crop

400mm + 1.4x converter upszied 100% crop

By the looks of this group of images, the 400mm + 2.0x extender is the best result. It is considerably sharper than the others and has managed to retain more details. The house in the shot is probably 1000 meters away, so it is a bit more of a ‘real life’ test than the first set up where the wicker box was only a couple meters away from the camera. I will also admit that I may of had problems focusing in the first set of test images. Although I took a number of shots with each set up, I only focused once. In the second trial, I re-focused for each shot and chose the best. The group of images that had the largest variance was the 400mm + 2.0x extender for the simple fact that it is hard to focus with this long of a lens. Autofocus is disabled with either extender so your focusing technique has to be spot on to get sharp images. When using the 70-200 f/2.8 lens you can autofocus with both extenders.

Conclusion: Well I have learned a few interesting things here. I am glad I bought the 100-400mm lens. It appears quite sharp considering it’s wide focal length range it shoots and is much better than any of the other compared methods at reaching 400mm. I am also glad I bought the extenders. The DO produce a sharper image than without the extender (after upsizing) and although they are tough to focus they are worthwhile if you have the time and set up to do so. If I was out on a shoot trying to hand hold the camera, I would forget the extenders and just shoot with the 400m lens and upsize if I had to. The autofocus would be worth a lot when it came to getting the shot. If I was out with a bag of gear, which included a good tripod, I would also bring along the extenders. They do their job well – they just complicate the procedure a bit.

….. Anyone want to buy an extender? I have 2 for sale On second thought, I think I’ll keep them.

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As a side note, for those who wonder if mirror lock up is ‘really necessary’. I would give a resounding yes. That and a cable release. When shooting at 800mm, even from a very sturdy tripod, if you look through the viewfinder when you click the shutter, you can see the lens wobble considerably. I was suprised at how much it moved. So make use of mirror lock up, or better yet, live view shooting.