Photo Jottings

Here’s a brief look at the Sony 85mm F/2.8 SAM lens.  Scroll down for the main review.

Box and contents

Side shot fully drawn in

Side shot fully extended

Backside plastic mount.

Deep front element

Sony X-ray view and MTF chart

The Sony A700 and Sony A900 were used for this review.  For a better understanding of terms and methods used in this review, go here.

This inexpensive full-frame compatible lens (made in China) features a relatively fast aperture of F/2.8 with a good fit and finish, although it has a plastic mount instead of the usual metal.  Sony calls the 85mm F/2.8 an “easy choice lens,” which means cheap price but excellent optical qualities.

This lens will work great on your Sony full-frame digital camera, as it was designed for a full-frame camera.  It can also be used on an APS-C camera, and becomes a somewhat long 127.5mm focal length.

There are no ‘ED’ elements used in the construction of the lens, which is a surprise based on the performance.

Focusing.  The focusing ring is at the front of the lens, and does turn during auto-focusing, so watch your fingers.  The filter ring does not turn, so your grads and polarizers will work fine.  Manual focusing takes just over 1/2 turn from Close-in to infinity, and adds 3/4″ or 20mm in length to the lens at close focus.  With over half a turn of focus ring rotation, it’s pretty easy to achieve accurate focusing using the manual ring.  There’s a tiny bit of slop on the focus ring if you wiggle it by hand when engaged, or disengaged, this doesn’t affect AF operation though.  Auto-focusing is quite loud when running from one end to the other, and not whisper quiet like the real Supersonic wave motors (SSM) on some of Sony’s other lenses.  Unfortunately, that’s the nature of Sony’s SAM or “Smooth Auto-focus Motor.”   Note on manually focusing; be sure to use the barrel mounted AF/MF switch to de-couple the focus ring, you cannot use DMF or the thumb switch (on select Sony cameras); that just makes the AF inoperable, but does not de-couple the focus ring; turning the focus ring while still engaged may damage internal components.

In the box is the lens, caps, hood, and owner’s manual with a warranty card, no case or pouch.

Lens flare/ghosting.  Above average control of ghosting among prime lenses.  I see a green blob if the sun is at the edge, or inside the image, but it isn’t bad at all.  Flare is a little heavy, so watch out if the sun is anywhere near the front element.  Use your hand or the supplied hood to try and mitigate the problem.  See samples below.

Color fringing (CA).  About average control, look for moderate amounts of lateral color fringing near the edges, only visible at large viewing sizes.  I see the typical fast lens, wide-open axial color fringing at F/2.8, but diminishes to almost nothing by F/4.

Bokeh.  Somewhat smooth at all apertures, but a light ring is visible around the highlights.  The aperture shape starts to show up between F/4-5.6.  Look below for sample crops.

Color.   Same as other Sony lenses.

Close up filter.  +4 tested and allows you to get a little closer.

Coma.  No coma at all on APS-C camera, and only a tiny insignificant amount on full-frame at F/2.8.

Regular filters cause no additional light fall-off problems.

Filter size is 55mm.  Other Sony lenses that use 55mm filters are; 100mm macro, 50mm macro, 50mm F/1.4, 35mm F/1.4 G, 18-70mm, 18-55mm, 55-200mm, 35mm F/1.8, and the 75-300mm.

Distortion.  Very straight on APS-C, and only tiny pincushion on full-frame.  Check out the cropped sample below.

Distortion example directly below.

No distortion.

Bokeh, or background highlight blur is generally good, although I see a slight ring around the highlights at all apertures.  I see some spherochromatism, meaning green tinged out of focus highlights in the background, and magenta tinged in the foreground.  This isn’t something to worry about.  Crops above were taken from the center of the image, focused about 7′ (2.1m), with the background about 18′ (5.5m) away.

Lens flare/ghosting examples

I see a green blob (top left shot near center) when the sun is close, or inside the image at certain angles and exposure values, and obviously more visible depending on background, but overall, good control of ghosting.  With the sun centered, there is no wagon wheel or disc visible.  Flare control is only average at best, so watch out when the sun is anywhere near the image.  Make sure you use the included hood, or your hand to block the sun if possible, examples of this on last row.

 Light fall-off.

When using an APS-C camera, there is no real light fall-off to worry about.  Results are about the same when focusing close-in, or far away.

Center sharpness.

Below are crops from the image centers.

Center sharpness is very good, even with the aperture wide open.  I see a little veiling haze at F/2.8, but it doesn’t show up unless viewed at huge sizes.  All shots in this section are taken at infinity focus.  Diffraction causes softening at apertures smaller than F/8.

There is some minor softness in the mid-sections at F/2.8, with quick sharpening as you stop down to F/4, at which point the mid-sections are almost as sharp as the centers.

Corners.

The extreme corners look slightly soft at F/2.8, but sharpen up by closing the aperture down to F/4.  F/8 is just barely the sharpest at the very edges.  The corners are almost as sharp as the mid-sections when stopped down; in fact the whole image looks very sharp at F/5.6-8.  Check out the last row where I show the center and corner crops side-by-side as comparisons.  All crops above were taken at infinity focus, about 350′ (107m) away.

F/5.6 color fringing, from right middle edge of image to 700 pixels in.

I see moderate amounts of lateral color fringing along the edges of the image.  Mostly magenta is visible, but cyan is also present.

This is the axial color fringing I was talking about at the beginning of the review.  This type of color fringing occurs all over the image, not just along the sides, (which is called lateral).  Axial color fringing goes away by stopping down the aperture.  It does show up at F/2.8, but is almost gone by F/4.  This is a little more than one would expect in a prime lens, but is not very noticeable unless viewed under harsh conditions as you see above with the sun shining off a truck door.

Let’s check out the macro capabilities of this lens.

Below, check out the cropped image (315kb) of the stamp.  The sample shot was taken with the Sony A 700 12.2MP camera.  The subject is a standard US stamp, 0.87″x 1.0″ or 22mm x 25mm.  Also, note the macro shot was taken as close to the subject as focusing allowed; in this case a somewhat long 18.5″ (470mm), measured from the front of the lens barrel to the subject.

As close as you can get, F/5.6. Click for full image.

 

Full frame section next.

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Full frame results using the Sony A900 below.

Check out the differences when using a film or full frame camera below.  I’m only pointing out the noticeable issues as compared to the APS-C bodies, so if I don’t show it here, the results are not significantly different enough to warrant posting an additional set of images in this section.

Light fall-off

Light fall-off is definitely stronger with full frame coverage.  I see moderate to heavy levels at F/2.8, however, by closing the aperture one stop, the dark corners begin to clear up nicely.

Full image below illustrating light fall-off from A900.

This full scene shows actual-use light fall-off.  It’s really not too noticeable, and certainly not distracting in my opinion.  This bright daylight scene would normally be shot around F/5.6, and light fall-off would be mostly gone.  Data for the image is; F/2.8, 2500sec, -0.30eV, ISO 200.

Center sharpness.

Below are crops from the image centers.

Again, center sharpness is very good wide open, but this time I’m using the full-frame A900.  I see a little veiling haze at F/2.8 but it doesn’t show up unless viewed at huge sizes.  Check out the aliases starting to show up at F/2.8 in the cactus arm tip above the yield sign, which indicates the widest aperture is very sharp.  Diffraction causes softening at apertures smaller than F/8.

 Crops from the mid-sections.

There is some minor softness in the mid-sections at F/2.8, with gradual sharpening as you stop down to F/5.6, at which point the mid-sections are almost as sharp as the centers.

Corners.

The full frame corners are a little soft and dark at F/2.8, but sharpen up nicely at F/5.6, as a side note; I threw in a couple of mid and center crops in the bottom row so you can see just how well the whole image holds up using a full-frame camera.  Crops taken from the last 300 pixels of the lower left corner.  Exposure differences are from light fall-off.  Notice the cyan color fringing along the left side of the Saguaro cactus in the mid/corner crops.

Distortion next

Flat to very minor pincushion distortion on A900

I see almost no distortion with full frame coverage, although people taking pictures of straight lines and applying a grid overlay will see very minor pincushion distortion.

Sony comes up with another winner in their high performance, low cost “easy choice” lens series.  This time it’s a medium telephoto prime with a relatively fast F/2.8 aperture.