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SMC Pentax-FA 100-300mm F4.5-5.6

Reviews Views Date of last review
11 61,182 Fri December 30, 2016
Recommended By Average Price Average User Rating
91% of reviewers $94.70 6.91
SMC Pentax-FA 100-300mm F4.5-5.6

SMC Pentax-FA 100-300mm F4.5-5.6
SMC Pentax-FA 100-300mm F4.5-5.6

The SMC Pentax-FA 100-300mm F4.5-5.6 lens features the power zoom function; its build and optics are otherwise identical to the F-series counterpart.

SMC Pentax-FA 100-300mm F4.5-5.6
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (A setting)
Automatic, 9 blades
12 elements, 8 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
AF (screwdrive)
Min. Focus
150 cm
Max. Magnification
Filter Size
58 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 16-5.5 ° / 14-4.6 °
Full frame: 24-8.2 ° / 20-6.9 °
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Power Zoom
Diam x Length
72 x 155 mm (2.8 x 6.1 in.)
605 g (21.3 oz.)
Production Years
1992 to 1998
Engraved Name
smc PENTAX-FA 1:4.5-5.6 100-300mm
Product Code
User reviews
Screwdrive AutofocusPowered ZoomingAperture RingAutomatic ApertureFull-Frame SupportDiscontinued
Price History:

Add Review of SMC Pentax-FA 100-300mm F4.5-5.6
Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-11 of 11

Registered: August, 2012
Posts: 523
Lens Review Date: December 30, 2016 I can recommend this lens: Yes | Price: $48.00 | Rating: 8 

Pros: Long reach, Power Zoom (on certain cameras)
Cons: long, heavy, power zoom not compatible with all cameras
Sharpness: 7    Aberrations: 8    Bokeh: 8    Autofocus: 8    Handling: 7    Value: 8    Camera Used: Kx, K10D   

So my immediate reaction to this lens when I first got it was one of frustration. When I first snapped it onto my Kx, it wouldn't zoom and I thought it was broken. But thanks to Sankon's review below, I quickly discovered the hidden secret of this lens. The zoom ring has two positions. Click it back toward the camera body and it functions as a conventional zoom ring. Click it forward and it functions as a rocker switch, activating the power zoom feature, but only on certain camera bodies. There are no markings on the barrel to indicate this and my lens came with no documentation, so I was pretty frustrated to find that only one of my four Pentax camera bodies, the K10D, supports the Power Zoom function and until I figured out how to put it into manual zoom mode, I thought I had a lens that would work with only one of my camera bodies. That said, I am relieved to report that the lens is fully functional and the Power Zoom feature is pretty fun to use, giving the camera a nice, high-tech feeling as it operates like any run-of-the-mill point-n-shoot camera. But gee-whiz novelty features aside, what kind of pictures does it take?

My first impression upon snapping this beast onto the front of a camera is it's very heavy, almost too heavy. Whenever I first put the lens on a camera, the autofocus has trouble engaging and once it does, it momentarily makes an unpleasant grinding noise but when everything is finally engaged, it works quite well. Image quality leaves a bit to be desired. The Focus is a little on the soft side and colors have a slightly yellowish hue. In one shot I took, there appeared to be a slight back focus but I've hardly shot enough with this lens to create a statistically significant sampling. My initial impressions are positive and I try to keep my expectations realistic. This isn't, after all, a $1,500 lens and it yields results commensurate with the price that I paid.

Update: 9 Jan. 2018: So I've had this lens for a little over a year and I still haven't exactly warmed to it, although I have since discovered the yellowish hue was not an issue with the lens but with incorrect white balance on my K10D, which is now corrected. It should also be noted that the $48 I paid for the lens was actually for an assortment of items that included this lens as well as another junk lens and a no-name flash. I sold the junk lens for $10 so my net for this lens and the flash is now $40.
New Member

Registered: December, 2016
Posts: 2
Lens Review Date: December 8, 2016 I can recommend this lens: No | Price: $90.00 | Rating: 3 

Pros: Light
Cons: Bad sharpness, poor contrast, lot of CA
Sharpness: 1    Aberrations: 4    Bokeh: 5    Autofocus: 8    Handling: 10    Value: 4    Camera Used: Pentax Kx   

Too expensive for the quality.

I was very disappointed with this lens, thanks to this piece of glass, I considered buying some old prime lens for the same price : Tair 3S and/or Petri 200mm F/2.8.

Anyway, at 100mm is just barely good... but not enought if you like sharpness.
Junior Member

Registered: October, 2012
Location: Toronto, Ontario
Posts: 37
Lens Review Date: September 29, 2013 I can recommend this lens: Yes | Price: $85.00 | Rating: 8 

Pros: Power zoom, good range, decently sharp, not too heavy, internal zooming
Cons: Not sharp at 300mm, Chromatic Aberrations,
Sharpness: 8    Aberrations: 7    Bokeh: 8    Autofocus: 9    Handling: 9    Value: 9    Camera Used: K-5II   

My first FA lens, which I picked up form a forum member here for $85. I need something with a bit more range, and this fit the bill. For $85 I am certainly willing to over look it's flaws, most of which only exist towards the end of the range, namely at 300mm. Once you get there, the fairly decent sharpness it had before kind of drops off, and there are noticeable CAs.

The power zoom is a very interesting feature. I enjoy that it focuses while you zoom,and I thought that would be helpful for sports, but having just tried to use it while shooting rugby, I would advise against it. It's easier to zoom manually and track the focus.

Other than that, it's not a half bad lens, and it's fairly cheap. If you need a lens with some reach, and don't mind the photos not being the sharpest at the long end, it's very good.
Forum Member

Registered: September, 2012
Location: Tokyo
Posts: 64
Lens Review Date: October 20, 2012 I can recommend this lens: Yes | Price: $60.00 | Rating: 9 

Pros: IZ ( Internal Zoom ), Cheap, switchable Power Zoom, Good handling
Cons: No bayonet hood. Filter thread rotates on focus. It's loooooong.

Bought this for 5000 yen, about US$60, from a Tokyo dealer. Appears to be in perfect condition. At the time I bought it, I didn't know about the powerzoom. In fact for several days after I bought it I still didn't know. For those as clueless as me - push the manual zoom ring forward a little, it will click and the zoom ring becomes a zoom rocker. Works perfectly, zooming at different speeds depending on how much the rocker is turned, on my K7. Haven't had much use for that, as I'm taking pictures of the stars with it mainly, but I understand it keeps focus as it zooms, which seems useful. Having said that, it seems to keep focus when manually zooming too. It's a good design. I prefer zoom rings to push/pull. Also, the size of the lens doesn't change when zooming, only when focussing. So there is only one moving entrance for dust or moisture to enter.

Pictures ? I'm comparing to my Takumar 135mm/f3.5 and 200mm/f4. I think it's sharper at 300mm than the 200mm Tak but not quite as good at 100mm as the 135mm Tak. Perfectly good enough. Differences more likely to depend on actual usage ( tripod or not, shutter speed, atmospheric conditions if shooting distance ) in the real world. It focusses to about 1.5m, much closer than the Tak 200mm ( 2.5m ). No fitting for a bayonet hood, just a 58mm thread. It's not a wide lens, nor heavy, but it is long ! Even without a hood. It balances very well indeed in the hand though, and with just the very front moving in or out a bit for focus, it helps ensure a steady shot as you zoom.

At the price, with good images and excellent handling, it is surely a good pick-up if you need a long telephoto.

New Member

Registered: August, 2011
Posts: 8
Lens Review Date: May 29, 2012 I can recommend this lens: Yes | Price: $160.00 | Rating: 8 

Pros: Good design, sharp, Great value
Cons: Perhaps a bit heavy
Sharpness: 8    Aberrations: 8    Bokeh: 7    Autofocus: 8    Handling: 8    Value: 8    Camera Used: Pentax K-5   

Having recently bought a copy of the relatively well regarded 80-320mm zoom, I decided to do some test shots comparing the two lenses - I really wanted (and expected) the 80-320 to be the clear winner - but it wasn't. I wanted a clear decision so that I knew which to sell and which to keep.

I may was unlucky with my copy of the 80-320, but wide open, the 100-300 Power Zoom seems generally sharper and have better CA control.

Also, because of the internal zoom design, the barrel it much shorter at the 300mm end, and it much easier to keep steady.

In addition, the Power Zoom has a unique feature that whenever you zoom, it maintains its focus or automatically re-focuses - this is actually really great leaving you to concentrate on framing the shot. Furthermore, you hardly have to move your hand at all to zoom due to the 3-speed zoom ring, again leaving the camera steady.

So upon comparison with the Pentax SMC 80-320, the 100-300 Power Zoom does not deserve the relatively poor rating it receives in these reviews.

With DSLR's being used for video, the Power Zoom features would be awesome if fully supported by K-5 & K-30 etc.
Inactive Account

Registered: August, 2010
Location: Texas
Posts: 2
Lens Review Date: September 29, 2010 I can recommend this lens: Yes | Price: $75.00 | Rating: 8 

Pros: Inexpensive,very quick zoom, good build
Cons: heavy and soft at the edges

No zoom creep that I could tell. I got this len for outdoor sports during the day and while the lens is slow it exceeded my expectations for nights under the lights.

Gee would I love to have an FA* 300mm F2.8 sure, but this lens costs $2,500 less.
It gets what I needed which is capturing memories not Sports Illustrated.

Photo was shot wide open F4.5, ISO 3200, 113mm, 1/125.
Loyal Site Supporter

Registered: November, 2007
Location: Nowhere Land
Posts: 2,330
Lens Review Date: August 17, 2010 I can recommend this lens: Yes | Price: $100.00 | Rating: 5 

Pros: Respectable Pentax image quality, it's got reach
Cons: Yeah, it's a bit heavy and long in length

In my reviews I like to point out that I do not study pixels closely. The lens delivers colors and contrast with sharpness every bit as good as many other Pentax lenses and competitors. Even without a lens hood, which is something considering how close the element is to the front
The lens works well to get close to your subject and bring you good images. It can produce a slight grating sound from the zoom and focus rings but this does not impede the speed of focusing. I would like the focus ring to have just a little more resistance when it's turned just for the feel I suppose.
The lens seems to find and lock on focus well enough even on my version 1 K10. It will shift in and out of focus less than other, smaller lenses.
Senior Member

Registered: December, 2008
Location: MN, US
Posts: 139
Lens Review Date: August 19, 2009 I can recommend this lens: Yes | Price: $109.00 | Rating: 8 

Pros: Price, build, sharpness
Cons: Heavy

Best telephoto zoom lens at 300mm reach for the price.
I compared the lens with Sigma DG 75-300mm Macro and Tamron XR LD 28-300mm.
All these 3 lenses are in same price range. The Pentax 100-300mm out perform the other 2 lenses in color and sharpness.
I rated it at 8 because that it is the best cheapest telephoto zoom lens at 300mm reach.
Veteran Member

Registered: March, 2009
Location: Salt Lake City, UT
Posts: 509

2 users found this helpful
Lens Review Date: April 20, 2009 I can recommend this lens: Yes | Price: $70.00 | Rating: 8 

Pros: long range, often underestimated
Cons: heavy and relatively flat image
Sharpness: 8    Aberrations: 7    Bokeh: 8    Autofocus: 9    Handling: 8    Value: 9    Camera Used: K10d   

I think people sometimes miss important points. We use lenses to shoot pictures instead of looking for small differences in picture quality. Me included.

Decent built quality. Image quality is more balanced than my fa 70-200mm especially at the long end. 70-200mm is very good for 150mm or less and struggle over that. This lens in contrast does not seem to excel at any length. But image quality is acceptable at any length, even at the largest aperture.

Less contrasty, sometimes due to far distance. Image a bit flat. Quite heavy and not well balanced sometimes. But it does not extend when zooming. We should spend more time shooting and less time comparing! Again, me included!

I am always more generous than average. That is how I grade my students.

EDIT: used more recently. Actually enjoy it more and more. Fast focusing and high contrast and great pictures. Photos with typical Pentax feeling. So revise it to a "8" for a zoom lens.
New Member

Registered: September, 2006
Location: Dallas, TX, USA
Posts: 21
Lens Review Date: April 8, 2007 I can recommend this lens: Yes | Price: $150.00 | Rating: 6 

Pros: good quality feel - durable - working power-zoom
Cons: soft at outer limits, heavy

This was my long telezoom for the Z1. I was happy with it until I compared the results to a no-name 200mm M42 prime on the same body. That brought me to replacing it with the 80-320.

Soft at the highest zoom - but still gets the birds in flight.

Well made and quite durable. I had it in service well over a decade.

Larry in Dallas
Veteran Member

Registered: November, 2006
Location: Sydney, Australia
Posts: 593
Lens Review Date: January 8, 2007 I can recommend this lens: Yes | Price: N/A | Rating: 5 

Pros: Good build quality
Cons: Poor sharpness
Sharpness: 6    Aberrations: 7    Bokeh: 7    Autofocus: 6    Handling: 6    Value: 5   

Whilst build quality is quite good from this mainly all metal lens, image quality is not as good. Needs to be stopped down to f8 to achieve good sharpness especially at the 300mm end. At shorter focal lengths, the sharpness is better.
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