Tokina 20-35mm F/2.8 AT-X 235 AF Pro Lens
f5fstop Basic Member
Sun 24-Sep-00 10:44 PM
Tokina 20-35 F/2.8 AT-X 235AF Pro Lens
Since purchasing the 235AF Pro lens it has turned into one of my favorite lenses for landscape photography. I purchased this lens to supplement my Tokina AT-X 270AF Pro lens and I have not been disappointed.
The 235AF Pro lens has internal focus, which means the lens stays the same size throughout the focusing range and the barrel of the lens does not turn. This allows the use of special effects and polorizer filters without having to readjust them each time you change focus. This lens, as well, as all Tokina AT-X Pro lenses, is a parfocal lens, which means the focus does not change from one focal length to another. Therefore, if focus is obtained on a subject at 20mm, then the lens is zoomed to 24mm or 35mm, the focus remains the same. With this feature auto focus times are reduced, when changing focal lengths, since the camera does not have to re-focus each time you change the focal length.
The 235AF Pro lens, as well as all new Tokina AT-X Pro lens Series lenses, uses a 77mm filter To obtain a constant F/2.8 aperture over an entire zoom range, the lens elements tend to be large. Therefore, if you use the AT-X line of lenses, you can share filters; this helps since these filters are rather expensive. Now I only have to carry around one set of filters. (Many other zoom lenses with a constant F/2.8 aperture across all zoom ranges also use this larger 77mm filter.)
I did purchase a narrow width UV and polorizer filters to use specifically with this lens due to vignetting at 20mm. The vignetting was so slim I could not see it when the lens was mounted on my F100 that had a 96 percent viewfinder view; however, it was noticeable when mounted on my F5 with a 100% viewfinder view. I never noticed any vignetting in my slides since you lose about 5% of the photo when the slide is mounted. However, it bothered me, so I went ahead and purchased the Hoya ultra-slim UV and polorizer filters.
The 235AF Pro lens includes a "tulip-style," bayonet-mount, plastic lens hoods that not only cuts down on light entering the lens from an angle, but also helps to protect the lens from possible damage.
The aperture scale, zoom range and distance scale markings are white on black and are extremely easy to read, even without my glass.
MANUAL/AUTO FOCUS ENGAGING (FOCUS CLUTCH MECHANISM)
The Tokina AT-X Pro lenses use a "Focus Clutch Mechanism" to switch between manual and auto focus. I have found this feature easier to operate than searching for a small button on the lens; which is used by some other manufacturers. To operate the focus clutch mechanism, slide the focusing ring forward (towards the end of the lens) engaging auto focus. To engage manual focus, slide the focusing ring back, and manual focus is engaged, disengaging the auto focus gears.
Auto focus can be engaged at any location on the distance scale; however, manual focus must be engaged at the same location on the distance scale, where auto focus was engaged. So to engage manual focus, rotate the focusing ring while applying slight pressure until the same location auto focus was engaged is located, and the ring slides back, engaging manual focus.
LENS OPTICAL QUALITY
From photos taken with this lens, the optical quality is great. The lens uses two multicoated aspherical elements; one for the front element and one for the rear element. To increase resolution and contrast, the lens elements are made of high-quality, high-refraction, low-dispersion (HLD) glass.
This use of aspherical and HDL elements helps produce extremely sharp photos with great contrast, in the entire aperture range at 20mm, and F8 to F16 for 28mm and 35mm (for print enlargements no larger than 16 x 20). Flaring has not been a large problem with the lens; however, there is some minor flaring at times, when the sun is in just the right (wrong) position. However, flaring is kept to a minimum, primarily due to the multi-coating, I believe.
Primarily, I use Fuji Velvia and Provia, Kodak E100VS, and Agfa RSX-II 200, and have had many photos enlarged via Ilfochrome process to 8 x 12 and a few to 16 x 20. The slides and photos display excellent sharpness and contrast. Since I primarily take only landscape photos, if there is any pincushion or barrel distortion I would not notice it, since Mother Nature has no straight lines.
As I have said in other write-ups on Tokina AT-X lenses, here is where I honestly believe Tokina excels over all other non-OEM lens manufacturers. Other manufacturers may have great optical quality; however, I have never seen any other non-OEM lens manufacturers to have build quality as excellent as Tokina AT-X Pro series lenses. These lenses are manufactured with aluminum barrels with chrome-plated brass lens mount. A black rough (crinkle) type finish is applied to the lens and rubberized coatings are applied to the focus and zoom rings. The pattern on the two rings is different, and I guess in some situations this can help a person identify the different rings by feel. However, the older you get, the more callused your fingers are, so this difference in coating patterns on the rings does nothing for me. Besides, it is easy to figure out that the ring closest to the camera body is the zoom ring, while the one towards the forward end of the lens is for focusing.
Another nice feature about Tokina AT-X Pro lenses is when the focus clutch mechanism is engaged to manual focus, the focusing ring is dampened to allow for a "better feel" when manually rotating the focusing ring. Similar to what a true manual focus lens feels like. The zoom ring is also very smooth to operate.
In my opinion, in this day-and-age, with modern equipment, the manufacture of lens elements is not as difficult as it was in the past. For this reason, non-OEM lens manufacturers can produce lenses that produce excellent quality photographs. Where I believe the non-OEM manufacturers differ greatly with OEM manufacturers is the actual build quality. However, from my experiences, the build quality of the Tokina AT-X lenses is as good as the build quality of a Nikkor lens. I would like to mention that I am talking pro series zoom lenses versus pro series zoom lenses. The lenses are marketed at the pro or serious amateur, and are usually considered "fast" lenses and are constructed to take a punishment. When I say "fast" lens, I am referencing lenses that have large apertures and in most cases, not all, the aperture is constant across all focal lengths.
All OEMs produce what is commonly called a "consumer" zoom lens. These "consumer" zoom lenses are manufactured using hybrid plastics, they are lighter, usually have a variable aperture across the focal lengths and are considerably less expensive than pro series lenses.
The following specifications for the AT-X 235AF Pro lens is taken from a Tokina Advertising Brochure; however, I did some revisions to commonize the specifications such as the order of the specification in the list, metric first, etc., but no actual specification is changed.
Focal Length: 20-35mm
Maximum Aperture: F/2.8
Minimum Aperture: F/22
Optical Construction: 15 Elements / 11 Groups (2 aspherical lenses at front and rear elements.)
Diagonal Angle of View: 93°38'(at 20mm)-63°13'(at 35mm)
Closest Focus Distance from Film Plane: 0.5m (1.64ft)
Lens Coating: Multi-coated on 13 elements
Filter Size: 77mm
Diameter: 84.0mm (3.3")
Length: 85.5mm (3.4")
Weight (approximate): 585g (20.6oz)
Lens Hood: BH773
Tokina 235AF Pro Lens: $699.95*
Nikkor** 20-35 F/2.8: $1399.95***
* Price obtained from B&H and Adorama
** Believe lens has been discontinued
"Take only photographs, leave only footprints"