|Pentax 300, 400, and 600mm|
|FA* 300 f/2.8|
|A* 300 f/2.8|
|A* 400 f/2.8|
|A* 600 f/5.6|
|Pentax-A 400mm taken f/3.5 @ 1/125|
|Pentax-A 400mm taken f/3.5 @ 1/125 Digital Crop|
|400mm with 1.4x-L converter f/4 @ 1/40th|
|Pentax-A 600mm f5.6 taken at 1/60 @ f/5.6|
|400mm f2.8 @ f3.5-1/160|
|400mm with 1.4x-L converter f/2.8 @ 1/100th|
|400mm with 2x-L converter f/2.8 @ 1/80th|
|400mm w/2x-L stacked w/2x-S extender f/2.8 @ 1/100th|
|400mm Optical crop to match stacked converters|
|400mm Optical with 2x-L rear converter full frame|
|400mm Optical with 2x-L rear converter cropped 50%|
|Steller's Jay. While the use of a converter is interesting, the Pentax-A 400/f2.8 will take stunning photos without such devices. This particular photo was taken at f/4, 1 1/100 sec. at ISO400 and is lightly cropped..|
|Bogen-Manfrotto 3046 Tripod w/3047 head|
|Pine Squirrel FA*300/2.8|
|Pine Squirrel FA*300/2.8 + Pentax AF 1.7x adapter|
While the lead in photo reflects 3 extreme telephoto lenses, my examples here only use two of them. I have compared the Pentax-A 400mm f/2.8 with the 600m f/5.6. I took the photos using a study tripod, and a remote release at distance of 50-60 feet under fairly dreary lighting conditions. It was late afternoon with heavy cloud cover just before a rainstorm hit.
I took the 600mm photo just with the basic lens. I used the 400mm 2 ways. In one instance I used the well regarded Pentax 1.4x-L teleconvter,(officially the Rear Converter-A 1.4x-L) which should extend the focal length 40%, and in the other I did a digital crop to effectively produce the field of view to equal the 600 mm. lens.
While the pictures are similar, The 'optical crop' using the 1.4x extender at this lighting level seems inferior to the digital crop. I would expect these results to be reversed if there was strong lighting. Likewise, the 600mm lens produced similar results to the 'optical crop' 400 and provided visibly less depth of field. There was some leaf movement due to a light breeze which may have also degraded the photos requiring the longer exposure times.
I'm really trying to validate when the use of various combinations is most appropriate. I'm getting the distinct feeling that the answer is not always the same.
The second tranche of photos (featuring the Red and white machine) represent a series of photos that I took on a cloudy but somewhat brighter day than the first group. Here I used the lens as presented, and with the 1.4x-L converter, and the 2x-L converter, and finally I stacked a 2x-S converter on the back of the 2x-L converter which I believe provides an effective focal length of 1600mm and finally, I digitally cropped (in photoshop)the first photo (with nothing) to match the stacked converter combination.
From observations, all the shots with converters show a little shadow suggesting some camera vibration. All are about the same, and it suggests to me that failure to lock up the mirror is the culprit. Likewise the stacked converters likely reduced available light beyond the range of the light meter resulting in a dark photo. (I did tweak the exposures some on this series in Photo shop.) As taken the Digital crop marginally beat out all of the converter combinations because of the lack of evidence of shake. My guess is that but for the shake issue, the results of an optical vs. a digital crop would produce nearly identical results. My observations here seriously call into question the value of the 'converters' which accomplish the optical cropping.
I would be quick to add that this does not mean that converters have no value. The two photos of the Red cow show otherwise. The first photo is taken with the A*400mm lens with a Pentax 2x-L converter and is shown full frame as the cow was well across the pasture. I then clipped the photo in Photoshop (digital crop) another 50%. If you expand the thumb nail photo, you can count the flies on the cows face and see eyelashes and the like--all of a cow that was several hundred feet from the camera.
Some ask if the converter should be used at all or if Photoshop should be relied on for all cropping. My answer to that is a definite maybe. You need the target image big enough to focus on. Indeed I actually attempted to take a photo of this cow without the converter at the same time, but it was so small in the view finder that I messed up the focus because I couldn't see it clearly. On the other hand converters are hard to work with. You need a very steady camera, and need to use mirror lockup options to prevent the mirror motion from vibrating the camera at the wrong time, and of course you need the best heaviest tripod you can get, or better yet, a concrete wall and a beanbag. I believe that if the lighting is good and strong you can get value out of using a converter. On the other hand if the lighting is weak, you better take the photo and do what you can in Photoshop.
These big lenses are not plug and play. As with any of the SMCA lenses that are manual focus, they do not have the electronics in them to tell the camera what lens you have attached so after installing the lens and turning the camera on you will need to manually input the focal length of the lens. This is needed to help the shake reduction to figure out how to behave. Do understand that if you then put the camera in a remote release mode, the camera will assume that you have it installed on a tripod and will disable the shake reduction.
The shake problem increases with the focal length of the lens, and if you are using a 600mm lens, by any definition its an extreme telephoto. Some sort of support is called for. Support may be what I call the bean bag solution which may be actually a beanbag, or a heavy coat, etc. on top of a a stationary object----You can aim the camera by rearranging the 'beanbag' and it will stay where you put it. More conventional solutions include a tripod and not just any tripod either. If the tripod is inexpensive, it is unlikely to be suitable. Tripods are rated for the weight they are intended to support, so one rated for the weight of one of these monster lenses is a must. The heaviest of the lenses that I have (the 400 f/2.8) is around 13 lbs (6kg) and needs a in that class. They are typically several hundred dollars.
The 600 F/5.6 is particularly difficult to use even on a tripod because it is out of balance in that the tripod mount is not on the center of balance of the lens. Unless you use an offset adapter plate, this further means that not only is the lens heavy, but nose heavy making the system prone to tipping over with potentially fatal results to the lens, but also much more subject to vibration, and other bad things. The A*400 is shown in the tripod photo and it is pretty well balanced. Special thought needs to go into the type of head that you use on the tripod. A Ball head is not usually the preferred solution. Though once again, fairly spendy, the Wimberly gimbel type head has much to be said for it. This head has a pivot point above the lens letting the lens hang down from it, as a good alternative to attempting to balance the lense on top of the head.
These two lenses are both compatible with the 'long' (type L) converters. the significant compatibility issue is the fact that the long converter has a long optic that sticks in the back of the lens. Both of these lenses have the clearance so long converter will work. From a focal length standpoint they are at the dividing line in the Pentax documentation and the 'short' converter works well also. Use which ever one you have. With the FA* lens you will lose the autofocus function, but for the most part this isn't a really big deal, as long shots on a tripod usually include time to focus manually, and the FA* lens has the classic FA* clutch for the purpose. The beauty of an f/2.8 lens is that you have light to burn, and converters always burn some. I'm not a great fan of converters, but these fast lenses are certainly candidates for them. Usually you don't need as much as f2/8 for a long shot, profoundly with late model digital cameras such as the K5 that work very well at high ISO, so burning some light with a converter isn't all bad.
As for the Pine Squirrel photos on the right, both shots are 'full frame. One with a converter and one without. taken with the lense wide open. One might argue there were identifiable sharpness issues with the converter but at worst I would rate them minimal.