Tag Archives: Pentax 645D

Long Exposures and the Pentax 645D

I spent about three hours on New Year’s Day wandering around Cliff Gilker Park in Roberts Creek, BC. On the way back, a spectacular sunset greeted my arrival into Davis Bay. After working in a few photolabs for a combined total of nearly seven years, I thought I more than had my fill of sunset photos. Mother Nature still has some surprises!

The Pentax 645D has very low noise images in general, but I haven’t had the opportunity to really push it to the limits of the marked shutter speeds. The lowest user-selectable speed is 30 seconds. The image below was shot at 25 seconds f/11. I was pretty much tripping over the rocks at that point. It was dark! The subtle fill light in the rocks was from a single street light located at least 50 feet behind me. Fortunately for me, it was sodium vapor so the color matched the sunset quite nicely. This image was shot about 30 minutes after the sun dipped below the mountains on Vancouver Island. The city lights in the distance are Nanaimo.

As an aside, white balance can be an easy tool to altering the appearance and mood of an image. A cool white balance for images of people is seldom attractive unless going to a particular style. Warm it up a bit and the skintones look attractive.

For the image above, I played with the white balance setting on the camera then tweaked it further in Lightroom. The fluorescent setting can give quite an attractive appearance to this sort of image. As is standard on most DSLRs these days, the 645D offers further tuning on the cyan/blue versus yellow/red axis as well as the magenta versus green axis. Very handy!

Back to noise characteristics… I mentioned there was a street light behind me and to my right. It provided some fill on the rocks in the foreground, however the sky was changing quickly and the light was fading. To wait for better balance between the street light fill and the sky wasn’t going to happen. Plus it was cold. After a half hour crouched over the tripod I was done. No suffering for my art. Adjust in post.

Below is a 100% crop from the rocks near the waterline in the center of the image.

Bringing more detail into this area can be accomplished via a number of methods in Lightroom / Camera Raw or later in Photoshop. While I don’t favor the extreme brightening in the image below, it shows what lies in the shadows of a 645D image.

The Fill Light slider was moved to a setting of 50 from its default of zero. Noise reduction is at zero for Luminance and 10 for Color. Reducing the Color slider to zero shows some noise, however if you consider that the default setting is 25, I don’t feel zero is a realistic setting.

I think the engineers at Pentax should be lauded for the excellent long exposure noise characteristics of the 645D. (Kodak too, since they manufacture the sensor) Compared to some other cameras on the market, this looks great. To top it off, the long exposure noise reduction (dark frame subtraction) didn’t even kick in at 25 seconds. In other words, there was no waiting after each exposure before taking another. Wow.

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.

More thoughts on usability – Pentax 645D

As is the style with most DSLR’s these days, the Pentax 645D has a long list of custom settings. There are a couple that have become definite favourites of mine that help make creating photographs with this camera that much more intuitive.

There are front and rear control wheels (or “e-dials” in Pentax-speak). This is a similar design feature on most DSLR’s. As with many other cameras, they can be customized. For a Nikon user like myself, makes the camera faster to use since it can operate in a similar manner to the other cameras I regularly use.

I generally use Aperture Priority and occasionally Manual. There are two well thought out features regarding the e-dial customization.

1 – Separate settings for each of the exposure modes (With TAv & M, plus B & X grouped together)

2 – In Aperture Priority (Av), the front dial can be set to control the aperture and the rear dial can be set for either Exposure Compensation or ISO. The option for Exposure Compensation or ISO is particularly useful since these important functions can be controlled without looking away from the viewfinder. Great feature!

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!