Tag Archives: Lens Testing

smc Pentax-FA 645 45-85mm f/4.5 lens performance

In the quest for a lens with a focal length that would be considered close to normal, I tried the following two lenses:

  • smc PENTAX-DFA 645 55mm F2.8 AL SDM AW [IF]
  • smc PENTAX-FA 645 45mm F2.8

The first is the lens that was originally released with the Pentax 645D camera. While the image sharpness was fine at the centre, the soft edges were not acceptable for the type of work I do. Same comments are true for the 45mm lens. I returned both and purchased a 45-85mm zoom to see what it can do.

In my blog post on the 45mm fixed lens, I photographed a brick wall to see how the centre versus corner sharpness compared. The same wall is featured below with the 45-85mm set to 45mm and an aperture of f/8. Due to the closer camera to subject distance of the asphalt in the lower corners, I’ve chosen a crop slightly up from the bottom of the frame.

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 - overall view

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 – overall view

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 - top left corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 – top left corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 - top right corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 – top right corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 - bottom right corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 – bottom right corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 - bottom left corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 – bottom left corner

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 - bottom left corner with chromatic aberration adjustment enabled

Pentax-FA 645 45-85mm f/4.5 lens shot at 45mm f/8 – bottom left corner with chromatic aberration adjustment enabled

The crops from this image demonstrate the superior performance of the 45-85mm zoom compared to the 45mm f/2.8 fixed lens. The centre and corners, except for the top right, are consistently sharp and exhibit good detail. Focus was set to Auto as it is generally more reliable than my eye. Camera was on a tripod and ISO was at 200.

The second last image in the series shows the chromatic aberration that can show up with this lens when it is shot at 45mm. Turning on the correction in Adobe Lightroom (same as Adobe Camera Raw) eliminates the colour fringing very effectively. The lens exhibits barrel distortion which can also be removed by enabling the lens corrections.

I was very impressed with the performance of this lens at the wide end of the zoom range. In the more than three years that have elapsed since shooting this test and creating this post, I have shot with this lens extensively. Focusing manually is challenging with the slow maximum aperture, however I have found using autofocus is mostly reliable and any shortcomings in image sharpness have usually been related to insufficient depth of field or not choosing a focus point that maximizes the available depth of field.

 

Trying out the smc Pentax-FA 45-85mm f/4.5 lens

The pause in blog posts has not been due to lack of happenings, but rather quite the opposite. In the past few posts I’d been discussing the challenges in finding a decent mid-range lens for the Pentax 645D. I have written about the older FA 45mm lens. Most users are going to be disappointed by the performance of that lens. Similarly, the new “digitally optimized” 55mm lens also has poor corner sharpness. Twice bitten, now what?

I had read online about some users obtaining good results with the smc Pentax-FA 645 45-85mm f/4.5 zoom lens. This seems to go against the usual wisdom of a prime lens being sharper than a zoom, but I was willing to try anything at this point. My other option was to turn to a Pentax 67 lens with an adapter for the 645D and that was not a road I was interested in traveling just yet.

There is a camera retailer in the U.K that I had purchased my smc Pentax-FA 645 200mm f/4 lens from in December. Great prices and good service. I figured it was worth another email now that I was looking for the 45-85mm lens. Once again, Mifsuds was excellent to deal with and my lens arrived a little more than a week after my email was sent. I normally try to support my local dealers, however going that route in this case would have meant a 3X surcharge.

It’s worth looking at the recent prices on EBay to see what lenses are proving to be popular on the Pentax 645D. The 35mm, 45-85mm and 120mm Macro have all experienced stronger pricing since the 645D became available outside of Japan. It does not appear the 75mm has seen the same increases, although it is an excellent piece of glass as well.

Within a day of it’s arrival, I was out shooting with the 45-85mm lens. It is tougher to focus manually than the 45mm or 55mm lens since its maximum aperture is about one and a half stops smaller. The focus just doesn’t “pop” as well. This is not unique to this lens, however. It’s just a fact of using a slower lens.

So far, I’ve found the 45-85mm to be a good performer with the autofocus system in the 645D. Most images are in the “keeper” category, though keep in mind that I’m mostly shooting subjects that either don’t move or move very slowly. It’s possible to manually focus this lens successfully in good light.

In my next post I’ll show some examples with the 45-85mm. In the meantime, if you’re looking for a mid-range lens for the Pentax 645D, this is the one to go with or should at least deserve your strong consideration.

smc Pentax-FA 645 45mm f/2.8 review

After spending an hour with the 45mm on the Pentax 645D and capturing a variety of images, I headed back to the computer to evaluate the results. I’ve spent a over a week in denial. I’ve read online at the disappointing results of the manual focus version of this lens and somehow hoped the autofocus version wouldn’t be in the same boat. Not so.

Back to the brick wall…

Bear with me on these as there is a practical example at the end. For some users, the same soft detail in the corners issue that plagues the the 55mm may not be a characteristic that bothers them. When a client points out that the image is soft during a shoot, that is a huge problem in my books. 100% crops processed with sharpening but no lens corrections are below with f/stop noted underneath. The corner crops are shown from the lower left hand corner, however all four corners showed the same effect.

smc Pentax-FA 645 45mm f/2.8 lens on Pentax 645D – overall view

Center crop @ f/2.8 – soft, lacks in contrast

Center crop @ f/8 – improved sharpness and contrast

Center crop @ f/16 – sharpness is similar to f/8, little degradation from diffraction

Lower left hand corner @ f/2.8 – completely unusable (vignetting as expected)

Lower left hand corner @ f/8 – sharpness is improved, but doesn’t compare to the center

Lower left hand corner @ f/16 – still not delivering the detail of a 40MP sensor

Granted a photographer is not going to be making money shooting brick walls. As a more practical example, how does this affect image quality when shooting the front of a building? The excellent “Tapenade” restaurant in Steveston provides an example.

Positioned square to the building, this is the view of the south side.

Taking a center crop just to the left of the sidewalk and entrance shows good contrast and sharpness at f/9.

Sliding over to the left side of the image is another story. I’ve used Lightroom 3.3 to process the DNG files. Lens corrections were shut off to show a “truer” version of the results from this lens. I’m not averse to using technology wherever possible, so a version of the left side image will be shown with lens corrections turned on, too.

The grass and hedge are becoming a green blob without the detail shown in the center crop. There is also lateral (or transverse) chromatic aberration visible in the shutters. Turning on the lens correction feature in Lightroom 3.3 / Camera Raw 6.3 resolves this issue. Unfortunately it doesn’t improve the sharpenss.

While small JPEG crops don’t really cut it to show the issues being discussed here, the effects are certainly visible. Should you have sufficient bandwidth and want to see the original DNG files, they are available for download from the links below. Each files is nearly 70MB in size.

Brick Wall image with 45mm lens at f/8
Restaurant image with 45mm lens at f/9

The Pentax 645D is a very capable medium format digital camera. The larger sensor compared to the 35mm full-frame cameras and lack of an anti-aliasing filter gives the camera an edge when high quality glass is used. Lens choice is key with this camera and the 645D owner needs to closely evaluate not only what is sufficient for their requirements, but how their particular lens performs as manufacturing tolerances come into play. Also, with so many used 645 lenses on the market, you don’t always know the history of the second-hand lens you’re putting on your camera.

smc Pentax-FA 645 45mm f/2.8 arrival

I picked up my 45mm lens today for the Pentax 645D. Given the disappointing results with the new “digitally optimized” 55mm, I’m hoping this lens will fill the gap between my 35mm and 75mm lenses. If not, I’ll be continuing my quest for a decent “normal” focal length lens for this camera.

The rainy days have subsided once again, so I’m hoping to get a few photos shot tomorrow. As with the other lenses on the 645D, I’ll be particularly interested in corner sharpness as well as overall quality.

Pentax-FA 645 120mm f/4.0 MACRO on the 645D

A lens that is quickly becoming a favorite for image quality on the Pentax 645D is the 120mm Macro. I’ve been shooting with the autofocus version as I felt I’d rather have the option of using autofocus than having the strictly manual version. Given the relative bargains on the used market for Pentax 645 lenses, there wasn’t significant financial penalty to opt for autofocus.

I know the brick wall test takes a lot of heat online. And it should. Really? Is this what photographer’s spend their time doing? (FWIW, the tests below were shot tripod mounted, self-timer with mirror lockup, ISO 200, lens corrections disabled in LR 3.3 and sharpening set to Amount at 50%, 0.8 px radius, Detail at 50, Masking at 7.)

My approach has been to test the lens at a variety of apertures, then use it for personal as well as professional work. The product photography I have used it for leaves no doubt in my mind about using the 120mm Macro for critical jobs. It is sharp! As with any lens, you need to know where it shines. Wide open at f/4 isn’t where it shines. (100% crop from center of image)

There is vignetting and an overall softness. At f/4, you are definitely not getting 40MP worth of resolution out of the 645D. Stopping down to f/8, the lens really starts to shine. (100% crop from same center portion of the image)

Much better results. Vignetting is virtually gone at f/5.6, clearly gone at f/8. Sharpness is strong and remains so at f/11. The lower right corner is shown below.

It is not quite as sharp as the center. This improves slightly by stopping down to f/11.

Once the lens is stopped down to f/16, loss of sharpness due to diffraction starts to become visible. I don’t think it is unacceptable at f/16, however it’s there. Some users might object while others will not. At f/22, diffraction is clearly an issue. I’ve included a center crop from f/32 to illustrate the issue. Unusable in my opinion. If you need considerable DOF, then hopefully focus blending is an alternative.

Maybe some black gaffer’s tape over f/32 is appropriate? This isn’t going to cut it.

To summarize the Pentax-FA 645 120mm f/4 MACRO on the 645D:

f/4 – vignetting, soft image

f/5.6 – minimal vignetting, center almost matches sharpness at f/8

f/8 – very good sharpness in center, corners still slightly soft

f/11 – excellent sharpness in center, corners as good as they get

f/16 – slight loss of sharpness compared to f/8 or f/11

f/22 – strong loss of detail due to diffraction

f/32 – all but useless

In the coming days, I will post results from the 35mm f/3.5, 75mm f/2.8, and 200mm f/4 – all in the autofocus versions. A 45mm f/2.8 is on its way. I returned the 55mm “digitally optimized” lens that was purchased with the 645D. For much of the professional type of work I do, corner sharpness is critical. That lens just doesn’t have it.

And don’t worry, there will be more that just brick wall photos!