Photo Jottings

Here’s a brief look at the Sony DT 18-55mm F/3.5-5.6 SAM zoom lens.  Scroll down for the review.

Requisite product shots.

New Sony basic “DT” kit lens, 18-55mm F/3.5-5.6 SAM

New box design, no hood included.

Front element

Rear shot, plastic mount

New, and old kit lenses. full zoom and focus extention.

New and old

Sony X-ray view and MTF chart

The Sony A700 was used for this review.  To get a better idea about my review methods and terminology, go here.

This is the newest basic “kit” wide to telephoto zoom lens available for your Sony APS-C sensor camera, and isn’t designed to be used on full frame/film cameras, but will work using APS-C size capt. on Sony full frame cameras.  The Sony DT 18-55mm F/3.5-5.6 SAM replaces the Minolta designed DT 18-70mm F/3.5-5.6 Sony has been using since 2006.  The new Sony lens has an almost satin/flat black finish, the same as the 70-300mm G SSM.  It has a ribbed rubber zoom ring, and a rather short rubber focus ring.  Quality seem good, with a nice fit and finish, but the end of the lens barrel at full extension is a little wobbly, it doesn’t effect the picture though.  It has a plastic mount.  Note; Sony is not including a hood with this new kit lens, which is no big deal as the one they offer as an accessory (same as old 18-70mm hood) for $18 doesn’t do any good, so don’t buy it.  Odd notes; the new DT 18-55mm SAM is made in Japan, the DT 18-70mm was built in China.  Sony introduces a new look for their lens boxes, see above.

Zoom control is smooth and even, the barrel runs in and out at different lengths like most cheap kit lenses, and is fully drawn-in at 35mm.  It extends out a maximum of 3/4″ (20mm) at 18mm.  The focal length numbers are checked at; 18mm, 24mm, 28mm, 35mm, and 55mm.  The EXIF data is off at the marked 28mm, reading 26mm, and at 24mm, reading 22mm, but that’s no big deal, other readings match up fine.

This lens is the first using Sony’s new SAM or “smooth autofocus motor,” which is a really cheap version of the very good SSM or Super Sonic Wave Motor.  Unfortunately, it isn’t very smooth, and has the same amount of noise (or more) as the old screw drive system, oh well.  It doesn’t seem to focus more accurately or faster than the lens it replaces.  With good light, focusing is fast and mostly accurate, especially with the lens stopped down.  Low light focusing is a hit or miss affair with the A700, (the A900 is much better) which uses a AF illuminator, not the flash.  Models that use the flash for low light focusing may be quicker and more accurate.  See the conclusion for more information about my thoughts on the new SAM.  The filter ring turns when focusing so watch your grads and polarizers, though it doesn’t turn while zooming, that’s the same design as the old lens.  These kit lenses aren’t really made for manual focusing.  It takes about 1/5 turn from close focus to infinity, which is not as short (1/8 turn) as the 18-70mm.  The closest focusing distance from lens barrel to subject is 4″ or 102mm.

Additionally, you can’t use DMF, or “direct manual focus mode” with this lens, you must use the switch on the lens itself.  There is no instant auto-override as with SSM.  This is annoying to me, but again, oh well.  If you press your AM/MF thumb switch on  the A700, A900, it just switches off the AF,  you can still turn the focus ring, but it doesn’t de-couple, so you may damage the gears inside.  It tells you about this in the owner’s manual.

Aperture/focal length guide for the Sony DT 18-55mm F/3.5-5.6 SAM.  This lens has overlapping numbers, for instance; you can get F/3.5 or F/4 at 20mm, depending on tiny movements of the zoom ring, this is quite common.  Look below for guide.  Also, this lens miss-reads the marked 28mm length (reads 26mm) and 24mm, (reads 22mm) in the EXIF data, not a big deal, it’s only off a hair.

 

The new Sony DT 18-55mm keeps the aperture wider as you zoom out.  You’re still at F/4.5 at 35mm, with the old Sony DT 18-70mm, you’re at F/5.6 at 35mm.

 

Sony 18-55mm F/3.5-5.6 SAM below

Flare and ghosting.  Extremely good control here and one of the best in the Sony lineup.  The new and old lenses perform about the same at controlling ghosting, veiling glare and flare.  There are some small green blobs or arcs depending on aperture, angle from light source and zoom length.  See samples below.

This lens is multi-coated and has the regular green/magenta look, same as the old lens.

Filter size.  55mm.  This size is the most popular used on Sony lenses, others using this size are: 18-70mm kit lens, 55-200mm, 50mm F/2.8 macro, 100mm F/2.8 macro, 35mmF/1.4, 50mm F/1.4 and the 75-300mm.

Filter use.  There is a tiny amount of additional vignetting at 18mm using a regular filter.

Coma.  No issues, even at 18mm, F/3.5.  Marginally better than the 18-70mm lens.   See crops below.

Color.  Looks slightly green compared to the Sony 18-70mm kit lens.

Close-up type filters.  Works ok, there’s not much size advantage in using one, but you shouldn’t need it with the great close-focus ability of this lens, +4 tested.

Lateral color fringing.  Way above average, and much better control than the 18-70mm kit lens.  See small comparison sample crops below.

Moderate to strong barrel distortion. 18mm

Light to moderate pincushion distortion at 55mm.

Moderate to strong barrel distortion. 18mm

Light to moderate pincushion distortion at 70mm.

Barrel and pincushion distortion.  The distortion at 18mm is moderate to strong.  It disappears rapidly, and by 35mm it’s flat.  From then on pincushion starts, and results in light to moderate distortion at 55mm.  Nearly identical performance as the 18-70mm.  See pictures above.

Lens Bokeh.  The Sony DT 18-55mm F/3.5-5.6 SAM has a harsh background blur, especially towards the long end, similar to other wide zoom DT lenses, except the CZ 16-80mm.  See sample crops below.

light fall-off, directly below.  Very mild at 18mm and F/3.5, stopping down helps out, but there isn’t a problem, even wide open.  At the long end there’s no problem.  Very good control here for a kit lens, and marginally better than the Sony DT 18-70mm old kit lens.

 

Examples of color fringing and ghosting below.

 

The top cropped images compare color fringing at 18mm, F/5.6 between the two DT kit lenses, taken from the left border of the image.  The newer 18-55mm is obviously the best at controlling lateral CA, this type doesn’t go away as you stop down.  You can also see the difference in image color in these crops, the 18-55mm being more green than the magenta biased 18-70mm.  Also notice the new lens is sharper at the image periphery.

 

The two lower shots show ghosting control, which is very good, and about the same as the old DT 18-70mm.  The 18mm sun-in-shot image shows a green blob at the middle one o’clock position.  The 55mm end with the sun just out of the shot shows some slight veiling glare, with a faint green arc at the top right.  This is the worst of it, and is still far better than the majority of Minolta/Sony lenses.

 

Random shots below.

Bokeh looks just fair at the wide end, but harsh at the long end, this performance is about average for less-expensive “kit type” lenses.

The last row shows the lack of coma, again, it’s marginally better than the Sony 18-70mm.  Very good contol here.

Corner softness.

18mm corners below.

 

Things look darn good here, even at F/3.5.  There is no real difference in corner sharpness at wide angle by stopping down the aperture, even when looking at 100% crops.  I threw in a center crop so you can see how sharp the corners are, comparatively speaking.  The corner crops look different from the center shot because that’s the way a wide angle lens renders images at the corners.

 

55mm corners 

The 55mm corner crops respond slightly to stopping down, though the center crop looks sharper.  F/16 was about the same as F/11.

Center samples next.

 

No problems here at wide angle and F/3.5.  This lens controls veiling haze better than the 18-70mm from F/3.5-4.5, 18mm.

 

55mm centers.

There’s a slight lack of contrast at 55mm, F/5.6, one stop down produces the sharpest image, F/11 is the same as F/8.

Check out the close focus shot.

Below, check out the sample (718kb) and click to see a 100% cropped portion of the full image.  The sample shot was taken with the Sony A700 12.2MP camera.  The subject is a standard US stamp, 1″x 3/4″ or 25.4mm x 19mm.  Also, note the macro shot was taken as close to the subject as focusing allowed; In this case, 4″ or 102mm, measured from the front of the lens barrel to the subject.

The new Sony 18-55mm SAM lens has a large reproduction size at 0.34x.  It did a good job at F/5.6, but the left side by the “2006” showed slightly soft, F/8 is the sharpest in the center with improved corners, F/11 turned in the sharpest all-around average.   This lens turned in the best close-focus stamp shot out of all the lenses I’ve tested so far, except for real (1:1) macro lenses!

100% crop, F/8, click me

 

Bonus section with comparisons to the Sony 18-70mm F/3.5-5.6 kit lens.

 

18mm centers.

 

As I said above, the 18-70mm has a bit less contrast than the 18-55mm when used at wide angle, and F/3.5.  Shots were taken at infinity, everything should be sharp, including the wall at the bottom of the crop.

 

18mm corners below.

 

The corners are sharper between F/3.5-5.6 on the new 18-55mm at wide angle, and color fringing is controlled better, making the difference more noticeable.

 

55mm centers.

 

The 55mm centers are noticeably sharper at F/5.6 on the newer 18-55mm.

 

55mm corners.

 

The 55mm corners from the old 18-70mm look slightly better, a surprise, but not noticeable unless viewed side-by-side.

 

70mm centers, upsampled for 18-55mm.

Here’s another surprise.  The 18-55mm is sharper in the center at 55mm than the 18-70mm is when set to 70mm.  I upsized the 55mm image from the 18-55mm to match that of the 70mm image from the 18-70mm.  So much for supposedly “losing” 15mm of focal length on the long end with the new lens.  This would only show up if you had your image enlarged to poster size, so don’t get too excited.  Note; the 18-70mm at 70mm was sharpest at F/11, the 18-55mm, at F/8, 55mm, that’s why I used those apertures for the crops above.  All images above were taken at infinity focus, so everything in the crop should be sharp

The Sony DT 18-55mm F/3.5-5.6 zoom is the basic, least expensive “kit lens” offered by Sony, and replaces the Sony 18-70mm F/3.5-5.6, which is a Minolta designed lens.  It’ll cost you between $50-$100 extra in the kit, or $199 by itself.  Build quality is rather cheap, but totally adequate for the intended purpose, an that’s for use by people just getting started in DSLR photography and don’t need focus scales, or non-rotating focus rings etc.

Optically, this lens is better in nearly every way than its predecessor.  Feel free to use the lens at any aperture, and zoom length and don’t worry about sharpness or color fringing.  If you shoot at or near 55mm, one stop down will produce the sharpest shots.  Macro shots are much larger and sharper than on the old lens.  Optically, Sony really did a good job re-designing their new “DT” kit lens.  I think it will easily match up to the Canon and Nikon in optical performance.  Do you wonder why I keep mentioning  the word “optical”?  Read on.

Auto-focusing performance is about the same as the old 18-70mm F/3.5-5.6.  That means the highly touted “SAM” or “smooth autofocus motor” is no better than the screw drive system in the old lens.  Here’s my opinion; the “SAM” was designed solely by Sony marketing people in a misguided attempt to try and keep pace with Nikon and Canon silent-wave and ultrasonic focusing systems etc.  Unfortunately, the “smooth autofocus motor” is just as loud (if not louder) than the screw drive system, and the “smooth” part is no smoother, there’s just as much “hunting and “jerking” in low light as the old lens.  Focusing accuracy is about the same, using wide or spot.  Bottom line; my Canon digital rebel from 2003 has a kit lens that’s much smoother, and quieter, with more accurate focusing (in low light) than the new Sony 18-55mm F/3.5-5.6 lens.  Sony decided to go cheap, and not utilize the proven, and excellent SSM focusing system.  Sony is gambling that potential customers (and current users) won’t notice stuff like this.  I think they may be wrong.  Hopefully a refined version is already in the works, with true SSM, plus, make the focus ring de-couple when using the thumb AF/MF button, (or DMF) instead of having to manually switch the lens button to “MF” to disengage (de-couple) the focus ring.

Don’t fret too much folks.  The lens is good, and the focusing is as good as the old lens.  Sony did a nice job optically, the SAM just needs major improvements.