Fujifilm X100S vs Pentax 645D

The Fujifilm X100S and the Pentax 645D are two digital cameras that were announced, respectively, in January 2013 and March 2010. The X100S is a fixed lens compact, while the 645D is a DSLR. The cameras are based on an APS-C (X100S) and a medium format (645D) sensor. The Fujifilm has a resolution of 16 megapixels, whereas the Pentax provides 39.5 MP.

Below is an overview of the main specs of the two cameras as a starting point for the comparison.

Headline Specifications

Fujifilm X100S		Pentax 645D
Fixed lens compact camera		Digital single lens reflex
35mm f/2.0		Pentax 645 mount lenses
16 MP – APS-C sensor		39.5 MP – Medium Format sensor
1080/60p Video		no Video
ISO 200-6,400 (100 - 25,600)		ISO 100-1,600
Electronic viewfinder (2360k dots)		Optical viewfinder
2.8" LCD – 460k dots		3.0" LCD – 921k dots
Fixed screen (not touch-sensitive)		Fixed screen (not touch-sensitive)
6 shutter flaps per second		1.1 shutter flaps per second
not weather sealed		Weathersealed body
330 shots per battery charge		800 shots per battery charge
127 x 74 x 54 mm, 445 g		156 x 117 x 119 mm, 1480 g

Check X100S offers at
ebay.com
Check 645D offers at
ebay.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Fujifilm X100S and the Pentax 645D? Which one should you buy? Read on to find out how these two cameras compare with respect to their body size, their imaging sensors, their shooting features, their input-output connections, and their reception by expert reviewers.

Body comparison

An illustration of the physical size and weight of the Fujifilm X100S and the Pentax 645D is provided in the side-by-side display below. The two cameras are presented according to their relative size. Three consecutive views from the front, the top, and the rear side are shown. All width, height and depth dimensions are rounded to the nearest millimeter.

The X100S can be obtained in two different colors (black, silver), while the 645D is only available in black.

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Pentax 645D is considerably larger (94 percent) than the Fujifilm X100S. It is noteworthy in this context that the 645D is splash and dust-proof, while the X100S does not feature any corresponding weather-sealing.

The above size and weight comparisons are to some extent incomplete and possibly misleading, as the X100S has a lens built in, whereas the 645D is an interchangeable lens camera that requires a separate lens. Attaching the latter will add extra weight and bulk to the setup.

Concerning battery life, the X100S gets 330 shots out of its Fujifilm NP-95 battery, while the 645D can take 800 images on a single charge of its Pentax D-LI90 power pack.

The table below summarizes the key physical specs of the two cameras alongside a broader set of comparators. If you would like to visualize and compare a different camera combination, you can navigate to the CAM-parator app and make your selection from a broad list of cameras there.

Body Specifications

		Camera Model	Camera Width	Camera Height	Camera Depth	Camera Weight	Battery Life	Weather Sealing	Camera Launch	Launch Price (USD)	Street Price
1.		Fujifilm X100S	127 mm	74 mm	54 mm	445 g	330	n	Jan 2013	1,299	ebay.com
2.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	9,995	ebay.com
3.		Canon 1D Mark IV	156 mm	157 mm	80 mm	1230 g	1500	Y	Oct 2009	4,999	ebay.com
4.		Canon 1D X	158 mm	168 mm	83 mm	1551 g	1120	Y	Oct 2011	6,799	ebay.com
5.		Canon G1 X	117 mm	81 mm	65 mm	534 g	250	n	Jan 2012	799	ebay.com
6.		Fujifilm X-Pro1	140 mm	82 mm	43 mm	450 g	300	n	Jan 2012	1,699	ebay.com
7.		Fujifilm X-T1	129 mm	90 mm	47 mm	440 g	350	Y	Jan 2014	1,299	ebay.com
8.		Fujifilm X-T10	118 mm	83 mm	41 mm	381 g	350	n	May 2015	799	ebay.com
9.		Fujifilm X30	119 mm	72 mm	60 mm	423 g	470	n	Aug 2014	599	ebay.com
10.		Fujifilm X100	126 mm	75 mm	54 mm	445 g	300	n	Sep 2010	1,199	ebay.com
11.		Fujifilm X100T	127 mm	74 mm	52 mm	440 g	330	n	Sep 2014	1,299	ebay.com
12.		Fujifilm X100F	127 mm	75 mm	52 mm	469 g	390	n	Jan 2017	1,299	ebay.com
13.		Leica S Typ 006	160 mm	120 mm	80 mm	1260 g	..	Y	Sep 2012	21,950	ebay.com
14.		Leica X Typ 113	133 mm	73 mm	78 mm	486 g	350	n	Sep 2014	2,295	ebay.com
15.		Nikon Coolpix A	111 mm	64 mm	40 mm	299 g	230	n	Mar 2013	1,099	ebay.com
16.		Nikon D3S	160 mm	157 mm	88 mm	1240 g	4200	Y	Oct 2009	5,199	ebay.com
17.		Pentax 645Z	156 mm	117 mm	123 mm	1550 g	650	Y	Apr 2014	8,499	ebay.com
Note: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
Convert to Imperial

The price is, of course, an important factor in any camera decision. The manufacturer’s suggested retail prices give an idea on the placement of the camera in the maker’s lineup and the broader market. The X100S was launched at a lower price than the 645D, despite having a lens built in. Usually, retail prices stay at first close to the launch price, but after several months, discounts become available. Later in the product cycle and, in particular, when the replacement model is about to appear, further discounting and stock clearance sales often push the camera price considerably down. Then, after the new model is out, very good deals can frequently be found on the pre-owned market.

Sensor comparison

The size of the sensor inside a digital camera is one of the key determinants of image quality. A large sensor will generally have larger individual pixels that offer better low-light sensitivity, provide wider dynamic range, and have richer color-depth than smaller pixels in a sensor of the same technological generation. Furthermore, a large sensor camera will give the photographer more possibilities to use shallow depth-of-field in order to isolate a subject from the background. On the downside, larger sensors tend to be more expensive and lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Fujifilm X100S features an APS-C sensor and the Pentax 645D a medium format sensor. The sensor area in the 645D is 295 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.5 and 0.79. The sensor in the X100S has a native 3:2 aspect ratio, while the one in the 645D offers a 4:3 aspect.

With 39.5MP, the 645D offers a higher resolution than the X100S (16MP), but the 645D nevertheless has larger individual pixels (pixel pitch of 6.06μm versus 4.80μm for the X100S) due to its larger sensor. However, the X100S is a much more recent model (by 2 years and 9 months) than the 645D, and its sensor will have benefitted from technological advances during this time that enhance the light gathering capacity of its pixel-units. Coming back to sensor resolution, it should be mentioned that neither of the two cameras has an anti-alias filter installed, so they are able to capture all the detail the sensor resolves.

The resolution advantage of the Pentax 645D implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the 645D for good quality output (200 dots per inch) amounts to 36.3 x 27.2 inches or 92.3 x 69.1 cm, for very good quality (250 dpi) 29.1 x 21.8 inches or 73.8 x 55.3 cm, and for excellent quality (300 dpi) 24.2 x 18.1 inches or 61.5 x 46.1 cm. The corresponding values for the Fujifilm X100S are 24.5 x 16.3 inches or 62.2 x 41.5 cm for good quality, 19.6 x 13.1 inches or 49.7 x 33.2 cm for very good quality, and 16.3 x 10.9 inches or 41.5 x 27.6 cm for excellent quality prints.

The X100S has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.

The Fujifilm X100S has a native sensitivity range from ISO 200 to ISO 6400, which can be extended to ISO 100-25600. The corresponding ISO settings for the Pentax 645D are ISO 100 to ISO 1600 (no boost).

In terms of underlying technology, the X100S is build around a CMOS sensor, while the 645D uses a CCD imager. The X100S uses Fujifilm's X-Trans layout of photosites, while the 645D employs the more common Bayer array.

For many cameras, data on sensor performance has been reported by DXO Mark. This service assesses and scores the color depth ("DXO Portrait"), dynamic range ("DXO Landscape"), and low-light sensitivity ("DXO Sports") of camera sensors, and also publishes an overall camera score. The adjacent table reports on the physical sensor characteristics and the outcomes of the DXO sensor quality tests for a sample of comparator-cameras.

Sensor Characteristics

		Camera Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Fujifilm X100S	APS-C	16.0	4896	3264	1080/60p	23.3	12.5	1329	75
2.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
3.		Canon 1D Mark IV	APS-H	16.0	4896	3264	1080/30p	22.8	12.0	1320	74
4.		Canon 1D X	Full Frame	17.9	5184	3456	1080/30p	23.8	11.8	2786	82
5.		Canon G1 X	1.5-inch	14.2	4352	3264	1080/24p	21.7	10.8	644	60
6.		Fujifilm X-Pro1	APS-C	16.0	4896	3264	1080/24p	23.1	12.3	1238	74
7.		Fujifilm X-T1	APS-C	16.0	4896	3264	1080/60p	23.5	12.7	1426	77
8.		Fujifilm X-T10	APS-C	16.0	4896	3264	1080/60p	23.7	12.9	1546	79
9.		Fujifilm X30	2/3	12.0	4000	3000	1080/60p	20.4	11.2	-312	49
10.		Fujifilm X100	APS-C	12.2	4288	2848	720/30p	22.9	12.4	1001	73
11.		Fujifilm X100T	APS-C	16.0	4896	3264	1080/60p	23.6	12.8	1483	78
12.		Fujifilm X100F	APS-C	24.0	6000	4000	1080/60p	23.9	13.2	1704	81
13.		Leica S Typ 006	Medium Format	37.5	7500	5000	none	23.9	12.2	824	76
14.		Leica X Typ 113	APS-C	16.1	4928	3264	1080/30p	23.6	12.8	1491	78
15.		Nikon Coolpix A	APS-C	16.1	4928	3264	1080/30p	23.4	13.8	1164	80
16.		Nikon D3S	Full Frame	12.1	4256	2832	720/24p	23.5	12.0	3253	82
17.		Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
Note: DXO values in italics represent estimates based on sensor size and age.

Many modern cameras are not only capable of taking still images, but also of capturing video footage. The X100S indeed provides movie recording capabilities, while the 645D does not. The highest resolution format that the X100S can use is 1080/60p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the X100S has an electronic viewfinder (2360k dots), while the 645D has an optical one. Both systems have their advantages, with the electronic viewfinder making it possible to project supplementary shooting information into the framing view, whereas the optical viewfinder offers lag-free viewing and a very clear framing image. The viewfinder in the X100S offers a wider field of view (100%) than the one in the 645D (98%), so that a larger proportion of the captured image is visible in the finder. On the other hand, the viewfinder of the 645D has a higher magnification (0.78x vs 0.43x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The following table reports on some other key feature differences and similarities of the Fujifilm X100S, the Pentax 645D, and comparable cameras.

Core Features

		Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Specifications (inch/000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Max Shutter Speed *	Max Shutter Flaps *	Built-in Flash (yes/no)	Built-in Image Stab
1.		Fujifilm X100S	2360	n	2.8 / 460	fixed	n	1/4000s	6.0/s	Y	n
2.		Pentax 645D	optical	Y	3.0 / 921	fixed	n	1/4000s	1.1/s	n	n
3.		Canon 1D Mark IV	optical	Y	3.0 / 920	fixed	n	1/8000s	10.0/s	n	n
4.		Canon 1D X	optical	Y	3.2 / 1040	fixed	n	1/8000s	14.0/s	n	n
5.		Canon G1 X	optical	n	3.0 / 922	swivel	n	1/4000s	1.9/s	Y	Y
6.		Fujifilm X-Pro1	1440	n	3.0 / 1230	fixed	n	1/4000s	6.0/s	n	n
7.		Fujifilm X-T1	2360	n	3.0 / 1040	tilting	n	1/4000s	8.0/s	n	n
8.		Fujifilm X-T10	2360	n	3.0 / 920	tilting	n	1/4000s	8.0/s	Y	n
9.		Fujifilm X30	2360	n	3.0 / 920	tilting	n	1/4000s	12.0/s	Y	Y
10.		Fujifilm X100	1440	n	2.8 / 460	fixed	n	1/4000s	5.0/s	Y	n
11.		Fujifilm X100T	2360	n	3.0 / 1040	fixed	n	1/4000s	6.0/s	Y	n
12.		Fujifilm X100F	2360	n	3.0 / 1040	fixed	n	1/4000s	8.0/s	Y	n
13.		Leica S Typ 006	optical	Y	3.0 / 922	fixed	n	1/4000s	1.5/s	n	n
14.		Leica X Typ 113	optional	n	3.0 / 920	fixed	n	1/2000s	5.0/s	Y	n
15.		Nikon Coolpix A	optional	n	3.0 / 921	fixed	n	1/2000s	4.0/s	Y	n
16.		Nikon D3S	optical	Y	3.0 / 921	fixed	n	1/8000s	11.0/s	n	n
17.		Pentax 645Z	optical	Y	3.2 / 1037	tilting	n	1/4000s	3.0/s	n	n
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One difference between the cameras concerns the presence of an on-board flash. The X100S has one, while the 645D does not. While the built-in flash of the X100S is not very powerful, it can at times be useful as a fill-in light.

The Pentax 645D has an intervalometer built-in. This enables the photographer to capture time lapse sequences, such as flower blooming, a sunset or moon rise, without purchasing an external camera trigger and related software.

Concerning the storage of imaging data, both the X100S and the 645D write their files to SDXC cards. The 645D features dual card slots, which can be very useful in case a memory card fails. In contrast, the X100S only has one slot. The X100S supports UHS-I cards (Ultra High Speed data transfer of up to 104 MB/s), while the 645D cannot take advantage of Ultra High Speed SD cards.

Connectivity comparison

For some imaging applications, the extent to which a camera can communicate with its environment can be an important aspect in the camera decision process. The table below provides an overview of the connectivity of the Fujifilm X100S and Pentax 645D and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.

Input-Output Connections

		Camera Model	Hotshoe Port	Internal Mic / Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
1.		Fujifilm X100S	Y	stereo / mono	-	-	micro	2.0	-	-	-
2.		Pentax 645D	Y	stereo / -	-	-	-	2.0	-	-	-
3.		Canon 1D Mark IV	Y	stereo / -	Y	-	mini	2.0	-	-	-
4.		Canon 1D X	Y	mono / -	Y	-	mini	2.0	-	-	-
5.		Canon G1 X	Y	stereo / mono	-	-	mini	2.0	-	-	-
6.		Fujifilm X-Pro1	Y	stereo / mono	-	-	mini	2.0	-	-	-
7.		Fujifilm X-T1	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
8.		Fujifilm X-T10	Y	stereo / mono	Y	-	micro	2.0	Y	-	-
9.		Fujifilm X30	Y	stereo / mono	-	-	micro	2.0	Y	-	-
10.		Fujifilm X100	Y	stereo / -	-	-	mini	2.0	-	-	-
11.		Fujifilm X100T	Y	stereo / mono	Y	-	micro	2.0	Y	-	-
12.		Fujifilm X100F	Y	stereo / mono	Y	-	micro	2.0	Y	-	-
13.		Leica S Typ 006	Y	- / -	-	-	mini	2.0	-	-	-
14.		Leica X Typ 113	Y	stereo / mono	-	-	mini	2.0	-	-	-
15.		Nikon Coolpix A	Y	stereo / mono	-	-	-	2.0	-	-	-
16.		Nikon D3S	Y	stereo / -	-	-	mini	2.0	-	-	-
17.		Pentax 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-

Studio photographers will appreciate that the Pentax 645D (unlike the X100S) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the X100S and the 645D have been discontinued, but can regularly be found used on ebay. The 645D was replaced by the Pentax 645Z, while the X100S was followed by the Fujifilm X100T. Further information on the features and operation of the X100S and 645D can be found, respectively, in the Fujifilm X100S Manual (free pdf) or the online Pentax 645D Manual.

Review summary

So how do things add up? Is the Fujifilm X100S better than the Pentax 645D or vice versa? The listing below highlights the relative strengths of the two models.

Reasons to prefer the Fujifilm X100S:

• Broader imaging potential: Can record not only still images but also 1080/60p movies.
• Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
• More framing info: Has an electronic viewfinder that displays shooting data.
• More complete view: Has a viewfinder with a larger field of view (100% vs 98%).
• Faster burst: Shoots at higher frequency (6 vs 1.1 flaps/sec) to capture the decisive moment.
• Ready to shoot: Comes with a built-in lens, while the 645D requires a separate lens.
• More compact: Is smaller (127x74mm vs 156x117mm) and thus needs less room in the bag.
• Less heavy: Is lighter even though it comes with a built-in lens (unlike the 645D).
• Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
• Faster buffer clearing: Has an SD card interface that supports the UHS-I standard.
• More affordable: Was introduced at a lower price, despite coming with a built-in lens.
• More modern: Reflects 2 years and 9 months of technical progress since the 645D launch.

Arguments in favor of the Pentax 645D:

• More detail: Has more megapixels (39.5 vs 16MP), which boosts linear resolution by 54%.
• Better image quality: Features bigger pixels on a larger sensor for higher quality imaging.
• Richer colors: The pixel size advantage translates into images with better, more accurate colors.
• More dynamic range: Larger pixels capture a wider spectrum of light and dark details.
• Better low-light sensitivity: Larger pixels means good image quality even under poor lighting.
• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.78x vs 0.43x).
• Easier setting verification: Features a control panel on top to check shooting parameters.
• Larger screen: Has a bigger rear LCD (3.0" vs 2.8") for image review and settings control.
• More detailed LCD: Has a higher resolution rear screen (921k vs 460k dots).
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• More flexible: Makes it possible to change lenses and thus to use specialty optics.
• Longer lasting: Gets more shots (800 versus 330) out of a single battery charge.
• Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
• Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
• Greater peace of mind: Features a second card slot as a backup in case of memory card failure.
• More heavily discounted: Has been around for much longer (launched in March 2010).

If the count of relative strengths (bullet points above) is taken as a measure, the 645D is the clear winner of the contest (17 : 12 points). However, the relative importance of the various individual camera aspects will vary according to personal preferences and needs, so that you might like to apply corresponding weights to the particular features before making a decision on a new camera. A professional wedding photographer will view the differences between cameras in a way that diverges from the perspective of a travel photog, and a person interested in cityscapes has distinct needs from a macro shooter. Hence, the decision which camera is best and worth buying is often a very personal one.

How about other alternatives? Do the specifications of the Fujifilm X100S and the Pentax 645D place the cameras among the top in their class? Find out in the latest Best Prime Lens Compact Camera and Best DSLR Camera listings whether the two cameras rank among the cream of the crop.

In any case, while the specs-based evaluation of cameras can be instructive in revealing their potential as photographic tools, it remains incomplete and does no justice, for example, to the way the X100S or the 645D perform in practice. At times, user reviews, such as those published at amazon, address these issues in a useful manner, but such feedback is on many occasions incomplete, inconsistent, and unreliable.

Expert reviews

This is why hands-on reviews by experts are important. The table below provides a synthesis of the camera assessments of some of the best known photo-gear review sites (amateurphotographer [AP], cameralabs [CL], digitalcameraworld [DCW], dpreview [DPR], ephotozine [EPZ], photographyblog [PB]). As can be seen, the professional reviewers agree in many cases on the quality of different cameras, but sometimes their assessments diverge, reinforcing the earlier point that a camera decision is often a very personal choice.

Expert Camera Reviews

		Camera   Model	AP   score	CL   score	DCW   score	DPR   score	EPZ   score	PB   score	Camera Launch	Launch Price (USD)	Street Price
1.		Fujifilm X100S	5/5	+ +	..	81/100	4.5/5	5/5	Jan 2013	1,299	ebay.com
2.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	9,995	ebay.com
3.		Canon 1D Mark IV	5/5	..	..	89/100	..	..	Oct 2009	4,999	ebay.com
4.		Canon 1D X	5/5	..	..	..	4.5/5	4.5/5	Oct 2011	6,799	ebay.com
5.		Canon G1 X	5/5	+	..	76/100	4/5	4.5/5	Jan 2012	799	ebay.com
6.		Fujifilm X-Pro1	5/5	+ +	..	79/100	4.5/5	4.5/5	Jan 2012	1,699	ebay.com
7.		Fujifilm X-T1	5/5	+ +	..	84/100	5/5	5/5	Jan 2014	1,299	ebay.com
8.		Fujifilm X-T10	4.5/5	+ +	..	80/100	5/5	5/5	May 2015	799	ebay.com
9.		Fujifilm X30	4/5	..	..	76/100	4.5/5	4.5/5	Aug 2014	599	ebay.com
10.		Fujifilm X100	3/5	..	..	75/100	4/5	5/5	Sep 2010	1,199	ebay.com
11.		Fujifilm X100T	5/5	+	..	81/100	4.5/5	5/5	Sep 2014	1,299	ebay.com
12.		Fujifilm X100F	5/5	+	3.9/5	83/100	4.5/5	4.5/5	Jan 2017	1,299	ebay.com
13.		Leica S Typ 006	..	..	..	..	..	..	Sep 2012	21,950	ebay.com
14.		Leica X Typ 113	3.5/5	..	..	..	3.5/5	4/5	Sep 2014	2,295	ebay.com
15.		Nikon Coolpix A	4/5	+	..	75/100	4/5	4/5	Mar 2013	1,099	ebay.com
16.		Nikon D3S	5/5	..	..	89/100	4.5/5	5/5	Oct 2009	5,199	ebay.com
17.		Pentax 645Z	5/5	..	3.5/5	..	4.5/5	5/5	Apr 2014	8,499	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

Care should be taken when interpreting the review scores above, though. The ratings were established in reference to similarly priced cameras that were available in the market at the time of the review. A score, therefore, has to be seen in close connection to the price and market introduction time of the camera, and comparisons of ratings among very different cameras or across long time periods have little meaning. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

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