Pentax SMC DA* 300mm f/4 SDM Lens – Featured User Review

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Pentax SMC DA* 300mm f/4 ED (IF) SDM telephoto lensLike everyone else, we spend the majority of our time and attention on Nikon and Canon camera gear. But there’s a lot of other great photography equipment out there. So here’s an excellent review for something different. The Pentax SMC DA* 300mm f/4 SDM telephoto lens is compact, light and weather-sealed, making it a great lens for outdoor photographers who want an easy to carry lens with a lot of reach. Pentax makes great digital SLRs and lenses and anyone shopping for their first DSLR would do well to take a close look at the Pentax system before they spend their money. If you own Pentax camera gear, please write reviews for your camera and lenses – your reviews are the foundation of this site!

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Featured Review: Pentax SMC DA* 300mm f/4 ED (IF) SDM Lens

by Scott (Intermediate)

Price Paid: $1100.00
Review Date: December 1, 2010
Used product for: 3 Months to 1 year

Overall Rating: 5 of 5
Value Rating: 4 of 5

I have pictures and such in my blog article on this lens:

What I like about the lens:
- While I have not scientifically tested the lens, I feel that it is sharp enough from it’s widest aperture and have never found an image that was was not good enough due to optical quality.
- It follows the tradition of Pentax rendering with vivid contrast. This lens is also very strong at controlling chromatic aberrations such as purple fringing.
- Seems very good at controlling flare, but I almost always use the lens hood.
- The bokeh can be beautiful (at times), especially in combination with a sharp subject producing a strong 3D effect.
- The lens seems bright throughout the whole frame event at the widest aperture (it is a full frame lens by design and has been confirmed “good enough” on with film cameras).
- The construction is top notch and one of the best lenses I’ve personally owned.
- SDM is quiet in focusing compared to screw-drive lenses.
- Quick-shift focus with a nice feature to have.
- Topnotch weather sealing.
- Small and light for it’s abilities relative to similar lenses.
- The lens is very versatile considering how long the focal length is, which is partly due to the short minimum focusing distance.
- I can easily hand-hold this lens and pan-focus on moving subjects.
- The lens is still very sharp and usable with a 1.5x Kenko teleconverter.

What I’m not too fond of:
- Maximum aperture of f4 is challenging at times with my K-7 because I like to keep the ISO low, but I’m not sure how much having f2.8 would really help…
- The lens isn’t cheap hovering around $1100, but good lenses hold value well.
- Pentax SDM hasn’t had the best track record, but my lens has been problem free. I did have two instances when I first got the lens where I needed to slightly rotate the screwdrive screw on the camera body after seeing that the lens locked up of sorts when I tried to auto-focus. For whatever reason the screw-drive connection wasn’t complete and held up the SDM from functioning. I’m guessing the screw drive connection in the lens was just a bit stiff initially (especially since the screw-drive bit isn’t used but on the oldest of camera bodies).
- Focus isn’t “lightning fast” with the K-7 and K10D, but it works fine. I think the K-5 might be better in this regard.
- Not specific to this lens as I have not had SDM issues, but I feel Pentax should allow users to select either SDM or screw-drive focus mode in the camera body. I have a feeling the lens would be faster in screwdrive mode as well.
- Bokeh can be wavy depending on the scene and conditions, which is most likely due to having sharper more contrast-y background blur or possibly just a property of the glass elements in how they handle the light and how you are facing a close background. I always use a lens filter, so I can’t say if it’s caused by that or just a property of the lens design.

Similar Products Used:
Tamron AF 75-300mm f/4.0-5.6 LD

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About the author: Photo-John

Photo-John, a.k.a. John Shafer, is the managing editor of and has been since the site launched back in 1999. He's an avid outdoor enthusiast and spends as much time as possible on his mountain bike, hiking or skiing in the mountains. He's been taking pictures for ever and ever, and never goes anywhere without a camera.

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  • Scott says:

    Thanks for featuring my review. I plan on adding more to your site in the future as I test out more of my lenses.

  • Photo-John says:

    Thanks for posting it, Scott! It’s a great review and we need more Pentax reviews and members. I would have e-mailed you to let you know if you’d been registered :-)

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