Discussion of Extenders for Canon DSLRs

This is in response to Abraham Lincoln's question about extenders to boost the range of his 70-200mm F4 L lens. First off there is no choice but to buy Canon in this case. Canon has a list of which lenses their extenders will work with. In some cases extenders will actually not physically fit the wrong lens, but in many it is that although they will fit, optical performance is unacceptable. It is generally accepted that one should buy extenders designed for a specific lens. I have been down the generic brand route before and it has never worked well.

The second point is somewhat controversial, but most consider the 1.4X to give acceptable results. I have found it to work well on the 70-200mm 2.8L and it is also recommended for the F4 version. Using the extender makes the lens about one stop slower. According to a chart I found, the 70-200mmF4 becomes a 98 -280 5.6 lens which equals a 156-448 mm film camera lens once one factors in the digital rebels 1.6X multiplication factor.

Most do not recommend the 2X extender. I have never tried it on the 70-200mm, but did extensively on the 500mmF4 early on and only got a few acceptable photos. It seemed I could get better results by using the 1.4X and cropping more severely in photoshop. Two seasoned photographers advised against buying it and I wouldn't listen.

Now for the confusing part. This test is by no means scientific and one must bear in mind the quality of pictures is hard to judge at the size we use them on the internet. The acid test would be to print them out.

A flock of Eastern Wild Turkey came into the meadow between 200-250 yards from me. (I still think of distance in a rifleman's terms) and I conducted this impromptu test with the Canon 40D and the 70-200mm 2.8. The birds were continually moving about but they stayed about the same distance. I didn't try for correct composition on the uncropped shots, but basically centered them. Images were shot in RAW and sharpened in Photoshop CS3 along with tweaking

levels. Everything was optimized for the best possible images: ISO 100, tripod, remote release and of course good lighting. Exposure was 1/500 f4.5 without extender and 1/350 f4.5 with extender.

200mm No Extender

200mm 1.4 Extender

200mm Cropped in Photoshop

200mm and 1.4X- Cropped in Photoshop

The bottom line is that it is hard to tell from these pictures if the extender is of value or not as the image holds up well to the cropping in both cases. Personally I wouldn't want to be without one. Although I don't use it often, it does come in handy. Perhaps the biggest lesson to be learned from this is that a photograph can be cropped quite tightly when a good lens is used and conditions are ideal.

Another possible option is the 100-400mm Canon L Zoom. I don't think it can be cropped as severely as the 70-200mm or the 500mm, but it is a very powerful lens which on the Rebel is 640mm 35mm equivalent on the top end. This is about a $1,400 lens. "Salty" is using mine at present and is quite happy with it. I know two other superb photographers who use it as well and all are pleased with it. On the down side it is a push-pull type zoom and gets longer as you zoom in, it also is not as sharp as a prime L lens and has only a 5.6 aperature when at maximum zoom. Its' big pluses is that it has IS, is reasonably sharp, and is a very powerful lens in a relatively small package. It is listed as being compatabile with the 1.4 extender, but it doesn't hold up too well with it and I prefer to avoid using the extender with it.

Here are some links for further information: All are to B&H Photo in New York.

1.4 extender

2x extender

Canon 100-400mm

A Discussion Of ISO In Digital Photography

ISO setting in regards to film is a rating that expresses the film’s sensitivity to light. Generally speaking a lower ISO such as 100 will give sharper images, more vivid colors, etc. In film days, the roll was rated at a certain speed, which could not be changed between shots.

With a digital camera ISO is a rating of the camera sensor’s sensitivity to light. The beauty of this is that the setting can be changed between shots to meet the photographer’s needs. In many cases the camera will select the speed automatically depending on the lighting conditions. In the earlier models of DSLRS (Digital Single Lens Reflex Cameras) this was not the case. The Canon 10D did not have this feature, but the 40D does. (I still prefer to make the decision myself). If the picture quality were better at the lower settings, why would one choose a higher one that results in diminished quality?

Things are fine as long as lighting conditions are excellent, but when one is photographing action scenes they must have sufficient shutter speeds to deal with the motion. In wildlife photography one often has to contend with both poor lighting conditions and subject movement. This involves compromises such as raising the ISO setting so that a satisfactory shutter speed may be obtained to stop the action.

Using a higher ISO may result in a softer looking picture with digital “noise” being visible. This usually appears as red and blue or green dots in the image with it being worse in shadow areas. DSLRS have made large strides in dealing with the noise through improved image processing in recent years so that it is possible to shoot at higher ISO settings and get more acceptable results than was previously possible. In fact some have said it is feasible to use many DSLRS at ISO 400 or 800 in all instances with little noticeable hit in quality.

One may also use post-processing tools, such as the noise reduction utilities built into Adobe Photoshop, or pug-ins such as Noise Ninja to remove noise, but we’ll try to keep this simple as possible and not go into that subject at this time.

We can address this in practical terms by talking about the photograph posted below.

It was very early this morning when these whitetail bucks came near me and started sparring. I decided to try IS0 500, which gave me a shutter speed of 1/180 at f2.8 with a Canon 70-200mm f2.8 L lens. Basically doubling the ISO rating will enable one to double the shutter speed, and cutting the ISO by one half will decrease the shutter speed by ½. Had I used IS0 200 I would have been at 1/90 or less and at 100 I would have been about 1/45. Even 1/180 is marginal for stopping this type of motion and 1/45 would certainly have resulted in blur unless I caught the animals at a moment of perfect stillness.





The good news is that if one shoots in decent light and situations that do not cause focus problems, that they do not need to concern themselves with many of these issues. As Wom Tigley pointed out in his response to my previous post he shoots a Canon S1, and uses a few basic settings and takes excellent photographs. By looking at his pictures I could not tell that he was using a point and shoot. “Salty” of Country Captures is another case in point and my Daughter “ASH”. Both have used the Canon S2 extensively with excellent results. Salty had a picture published in The Pennsylvania Game Commission Calendar and it fits right in with the others. No one would guess it was taken with a point and shoot camera. The main downside to these cameras is that ISO 400 is very noisy in poor light because of their small sensor size (the smaller the sensor all things being equal the more noise there will be) and their manual focus is difficult to use. This makes them less than ideal for wildlife photography, but they are an excellent choice for many tasks.

So much for the rant on ISO. I hope that clears things up for Wom, and others interested in the technical matters. If I am wrong or confusing on some of the above points, perhaps some of the knowledgeable DSLR photographers such as Abraham Lincoln, Salty, Chad Oneil, etc. can chime in an clarify things.