John Riley reviews the SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] vintage lens for full-frame SLR/DSLRs.
Posted: 16/09/2020 - 13:28
The SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] lens is a superior kit lens from around 2001, a little before the arrival of the crop sensor Pentax DSLRs. Thus it is designed for film cameras and does not sit particularly well with the APS-C format, where it would be a “35mm equivalent” 36-135mm; perhaps not wide enough for a general-purpose lens. However, it does sit very well as a standard zoom for full-frame and could be an interesting option compared to the expensive, heavy and bulky HD Pentax 24-70mm f/2.8 from the current range. Is it up to the mark? Let's find out, using the 36MP Pentax K-1 body.
SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] Handling and Features
The first impressions very clearly show us a compact, light lens, weighing in at a very modest 355g. There is a supplied and large bayonet fit lens hood that clips securely into place without the need for a locking catch. The hood has a small removable panel that enables the rotation of polarising filters with the hood in position, a nice touch that other marques have been slow to take up. The filter thread is a standard 67mm.
First up is a thin manual focusing ring and to use this the camera body will need to be switched to MF. There is no full-time manual focusing or QuickShift as Pentax describe it. The ring does rotate during AF operation, so the fingers should be kept away from it. Focusing is down to 0.5m, or 1.6 feet, for a maximum magnification of 0.18x. There is a clear distance scale, marked in feet and metres. There is no depth of field scale, but there are Infra-red correction marks for 24mm and 90mm.
The zoom ring is clearly marked at 24mm, 28mm, 35mm, 50mm, 70mm and 90mm. The action of this ring is smooth but has little resistance, so when carried it is quite likely that the lens will extend if pointed downwards.
Finally, closest to the body is the nicely clicked aperture ring, with an “A” setting for when the camera is to control the aperture. This is the setting used for DSLRs to give full function.
AF is by screw drive, so is hardly quiet, but it does move swiftly and accurately. The lens mount is Pentax's fine steel mount, this version complete with all mechanical and electronic connections.
Optical construction is 13 elements in 11 groups coated with the SMC (Super-Multi-Coated) multicoating of the era, which is very effective, holding up well when compared to current coating techniques. The diaphragm comprises 8 blades. As this is a film-era lens, it is likely that the exit light will not be telecentric, that is, parallel, which is what digital sensors prefer, so especially at wider angles and at the edges the lens is at an immediate disadvantage. Handling-wise, it's a gem, absolutely delightful in use, so it could be a winner if the optical performance is up to scratch.
SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] Performance
At 24mm, sharpness is very good centrally from f/3.5 to f/22 and holds very evenly throughout the range. The edges are only fair throughout, a combination of the lack of telecentric design and probably field curvature as well. As can easily be the case, the 3D real-world images look much sharper than the flat test chart pictures, highlighting that the chart test results are never the whole story.
At 35mm, central sharpness is very good from f/4 to f/16 and good at f/22 and f/29. The edges are fair at f/4, good at f/5.6, very good at f/8 and f/11, good at f/16 and fair at f/22 and f/29.
At 70mm, the centre is good at f/4.5, very good from f/5.6 to f/16, good at f/22 and fair at f/32. The edges are good at f/4.5, very good from f/5.6 to f/16 and fair at f/22 and f/32.
At 90mm, the centre is good at f/4.5, very good from f/5.6 to f/16, good at f/22 and fair at f/32. The edges are fair at f/4.5 and f/5.6, very good at f/8 and f/11, good at f/16 and fair at f/22 and f/32.
SMC PENTAX-FA 24-90mm f/3.5-4.5 AL MTF Charts
How to read our MTF charts
The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges.
The scale on the left side is an indication of actual image resolution and sharpness as LW/PH and is described in detail above. The taller the column, the better the lens performance.
For this review, the lens was tested on a Pentax K-1 using Imatest.
CA (Chromatic Aberration), as expected, strays somewhat at 24mm and the edges, again through the lack of a telecentric design, but is much better as we zoom in. The centre is highly corrected throughout. This can, of course, be tackled in software and is not always obvious anyway, depending on the subject matter.
SMC PENTAX-FA 24-90mm f/3.5-4.5 AL Chromatic Aberration Charts
How to read our CA charts
Chromatic aberration (CA) is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.
Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.
For this review, the lens was tested on a Pentax K-1 using Imatest.
Distortion is reasonable for a zoom lens of this era. At 24mm we find-2.18% barrel distortion. This soon changes to pincushion, which measures +0.36% at 35mm, +2.13% at 70mm and +2.23% at 90mm.
Bokeh hadn't been invented when this lens was designed, so we rely on the 8 diaphragm blades and the telephoto focal lengths top create smooth background blur. It's not bad at all, but not as smooth as more recent optics.
Flare is impressively low and the worst of it is just a lowering of contrast when shooting directly into the light.
Vignetting is very moderate for a zoom lens and the results are:
| Aperture | 24mm | 35mm | 70mm | 90mm |
| f/3.5 | -2.5 | |||
| f/4 | -2.2 | -0.9 | ||
| f/4.5 | -1.2 | -1.2 | ||
| f/5.6 | -1.5 | -0.7 | -0.8 | -0.9 |
| f/8 | -1.1 | -0.7 | -0.8 | -0.9 |
| f/11 | -1.1 | -0.7 | -0.5 | -0.7 |
| f/16 | -1.1 | -0.7 | -0.5 | -0.7 |
| f/22 | -1.1 | -0.7 | -0.5 | -0.6 |
| f/29 | -0.6 | |||
| f/32 | -0.5 | -0.6 |
SMC PENTAX-FA 24-90mm f/3.5-4.5 AL Sample Photos
SMC PENTAX-FA 24-90mm f/3.5-4.5 AL Aperture Range
Value For Money
Given that the obvious new alternative is the HD Pentax-D FA 24-70mm f/2.8 ED SDM WR at around £1049, the SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] is a real bargain for less than £200. We get a more compact lens and a longer focal length, but sacrifice QuickShift focusing, constant f/2.8 aperture, and weather resistance.
But at the price and given its versatility, value for money is sound.
SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] Verdict
We don't spend our lives photographing test charts, and this would be the wrong lens to use if we did. Central sharpness is very good throughout, the only problem being the indifferent edge sharpness. This is not as bad as it seems though, in that real-world 3D images are fine and the lens delivers clean, crisp images. Clearly the newer 24-70mm lens is a better performer, but at a much higher cost, but the option is there. As the lens is actually very usable, despite its foibles, it remains good value for money.
Flat subjects are not rendered as well at close distances, so this is not ideal for copying documents or test charts, for example. But 3D images in the real world are sharp and crisp with very pleasant bokeh and general rendering.
This reviewer has this lens on the K-1 for general shooting and it handles beautifully and is very versatile. It is also a perfect choice of focal lengths for the full-frame K-1, filling a gap by extending the focal length range when compared to the 24-70mm and 28-105mm alternatives. It can definitely be recommended.
SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] Pros
- Very good central sharpness
- Low central CA
- Modest vignetting
- Reasonably low distortion
- Fast AF
- Lovely handling
- Good VFM
- Very useful focal lengths
SMC Pentax-FA 24-90mm f/3.5-4.5 AL [IF] Cons
- No weather sealing
- Edge softness
- No QuickShift
- Some edge CA
- AF noisy
- Lens extends when carried
Specifications: SMC PENTAX-FA 24-90mm f/3.5-4.5 AL |
||||
| General | ||||
| Focal Type | Standard zoom | |||
| Lens Mounts | Pentax K SMC-FA | |||
| Availability | ||||
| Year announced | 2001 | |||
| Discontinued | Yes | |||
| Dimensions | ||||
| Diameter | 72mm | |||
| Height | 74.5mm | |||
| Weight | 355g | |||
| Construction | ||||
| Groups | 11 | |||
| Elements | 13 | |||
| Blades | 8 | |||
| Lens | ||||
| Stabilised | No | |||
| Filter Size | 67mm | |||
| Min Aperture | f/32 - 22 | |||
| Max Aperture | f/4.5 - 3.5 | |||
| Angle of View | 84 - 27° | |||
| Focal Length | 90 - 24mm | |||
| Focusing | ||||
| Macro | No | |||
| Min Focus | 50cm | |||
| Focusing Type | Automatic | |||
Members gallery photos using: smc PENTAX-FA 24-90mm f3.5-4.5 AL [ IF]
I love using it on a K5. It brings back that 70s feeling, when all I could afford was a second hand K1000 with the 1.8/55 kit lens plus a 35 wide angle and a 135 tele from Soligor. The limitations may be cumbersome in some situations but they make you think of points of view and fields of vision more than just having to turn the zoom ring to 18 or 300.
The downside really is that it is not of the same build quality as other Pentax lenses. It does feel a bit wobbly and noisy.
On the upside, the corner softness disappears, when used with an APS-C camera.
The front of the lens wobbled alarmingly, but it still produced wonderfully sharp pictures.
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10 years
NZ
I have owned two copies of this lens and I used it on my Pentax MZ-S 35mm film camera.. I also used it less often on Pentax crop sensor digital cameras, where, as your reviewer says, the focal length becomes less useful with a wide end of the zoom having the field of view of a 35mm lens. Later I used it as a walkabout lens for the K1 until I bought the DFA28-105 and the DFA24-70 lenses.
My subjective view was the lens out performed my DA 17-70mm lens at the 70mm setting. Not bad for a lens made for film cameras.
On the old Pentax lens site (BD)has a reference to "ghostless coating" that must have been an additional coating to take into account reflection off the sensor.
The one complaint I have is to do with build quality: there was substantial barrel wobble in both copies of the lens I bought. Other than that, it was a useful walkabout lens, being both lighter and smaller than the DFA lenses.