Leica S1 vs Pentax 645D

The Leica S1 Pro and the Pentax 645D are two professional cameras that were announced, respectively, in August 1996 and March 2010. The S1 is a mirrorless interchangeable lens camera, while the 645D is a DSLR. Both cameras are equipped with a medium format sensor. The Leica has a resolution of 26.4 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

Leica S1		Pentax 645D
Mirrorless system camera		Digital single lens reflex
Leica R mount lenses		Pentax 645 mount lenses
26.4 MP – Medium Format sensor		39.5 MP – Medium Format sensor
no Video		no Video
ISO 50-1,600		ISO 100-1,600
Optical viewfinder		Optical viewfinder
no LCD		3.0" LCD – 921k dots
no rear screen		Fixed screen (not touch-sensitive)
0.01 shutter flaps per second		1.1 shutter flaps per second
not weather sealed		Weathersealed body
339 x 214 x 119 mm, 2500 g		156 x 117 x 119 mm, 1480 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Leica S1 Pro 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

The side-by-side display below illustrates the physical size and weight of the Leica S1 and the Pentax 645D. The two cameras are presented according to their relative size. Three consecutive perspectives from the front, the top, and the back are available. All width, height and depth measures are rounded to the nearest millimeter.

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 smaller (75 percent) than the Leica S1. Moreover, the 645D is substantially lighter (41 percent) than the S1. It is noteworthy in this context that the 645D is splash and dust-proof, while the S1 does not feature any corresponding weather-sealing.

The above size and weight comparisons are to some extent incomplete since they do not consider the interchangeable lenses that both of these cameras require. Hence, you might want to study and compare the specifications of available lenses in order to get the full picture of the size and weight of the two camera systems.

The adjacent table lists the principal physical characteristics of the two cameras alongside a wider set of alternatives. In case you want to display and compare another camera duo, you can use the CAM-parator app to select your camera combination among a large number of options.

Body Specifications

		Camera Model	Camera Width	Camera Height	Camera Depth	Camera Weight	Battery Life	Weather Sealing	Camera Launch	Launch Price	Street Price
1.		Leica S1	339 mm	214 mm	119 mm	2500 g	..	n	Aug 1996	EUR 21 499	ebay.com
2.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	EUR 9 995	ebay.com
3.		Canon 1D Mark IV	156 mm	157 mm	80 mm	1230 g	1500	Y	Oct 2009	EUR 4 699	ebay.com
4.		Canon 1D X	158 mm	168 mm	83 mm	1551 g	1120	Y	Oct 2011	EUR 6 299	ebay.com
5.		Canon 250D	122 mm	93 mm	70 mm	449 g	1070	n	Apr 2019	EUR 549	amazon.com
6.		Canon RP	133 mm	85 mm	70 mm	485 g	250	n	Feb 2019	EUR 1 499	amazon.com
7.		Fujifilm X-T30	118 mm	83 mm	47 mm	383 g	380	n	Feb 2019	EUR 999	ebay.com
8.		Leica CL	131 mm	78 mm	45 mm	403 g	220	n	Nov 2017	EUR 2 490	ebay.com
9.		Leica M-E Typ 240	139 mm	80 mm	42 mm	680 g	500	Y	Jun 2019	EUR 3 949	ebay.com
10.		Leica Q Typ 116	130 mm	80 mm	93 mm	640 g	300	n	Jun 2015	EUR 3 999	ebay.com
11.		Leica S2	160 mm	120 mm	80 mm	1410 g	..	Y	Sep 2008	EUR 18 599	ebay.com
12.		Leica S Typ 006	160 mm	120 mm	80 mm	1260 g	..	Y	Sep 2012	EUR 19 499	ebay.com
13.		Leica TL2	134 mm	69 mm	33 mm	399 g	250	n	Jul 2017	EUR 1 949	ebay.com
14.		Nikon D3S	160 mm	157 mm	88 mm	1240 g	4200	Y	Oct 2009	EUR 4 999	ebay.com
15.		Pentax 645Z	156 mm	117 mm	123 mm	1550 g	650	Y	Apr 2014	EUR 6 999	ebay.com
16.		Sony A6100	120 mm	67 mm	59 mm	396 g	420	n	Aug 2019	EUR 899	ebay.com
17.		Sony A6400	120 mm	67 mm	50 mm	403 g	410	Y	Jan 2019	EUR 1 049	amazon.com
Note: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
Convert to Imperial

Any camera decision will naturally be influenced heavily by the price. The listed launch prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The 645D was launched at a markedly lower price (by 54 percent) than the S1, which puts it into a different market segment. 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 imaging sensor is at the core of digital cameras and its size is one of the main determining factors 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 are more costly to manufacture and tend to lead to bigger and heavier cameras and lenses.

Both cameras under consideration feature a medium format sensor, but their sensors differ slightly in size. The sensor area in the 645D is 12 percent bigger. As a result of these sensor size differences, the cameras have format factors, respectively, of 0.85 (S1) and 0.79. The sensor in the S1 has a native 1:1 aspect ratio, while the one in the 645D offers a 4:3 aspect.

With 39.5MP, the 645D offers a higher resolution than the S1 (26.4MP), but the 645D has smaller individual pixels (pixel pitch of 6.06μm versus 7.01μm for the S1). Yet, the 645D is a much more recent model (by 13 years and 6 months) than the S1, 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 Leica S1 are 25.7 x 25.7 inches or 65.3 x 65.3 cm for good quality, 20.6 x 20.6 inches or 52.2 x 52.2 cm for very good quality, and 17.1 x 17.1 inches or 43.5 x 43.5 cm for excellent quality prints.

The Leica S1 Pro has a native sensitivity range from ISO 50 to ISO 1600. The corresponding ISO settings for the Pentax 645D are ISO 100 to ISO 1600 (no boost).

Technology-wise, both cameras are equipped with CCD (Charged Coupled Device) sensors. Both cameras use a Bayer filter for capturing RGB colors on a square grid of photosensors. This arrangement is found in most digital cameras.

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 table below summarizes the physical sensor characteristics and sensor quality findings and compares them across a set of similar cameras.

Sensor Characteristics

		Camera Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Leica S1	Medium Format	26.4	5140	5140	none	..	..	..	..
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 250D	APS-C	24.0	6000	4000	4K/25p	23.9	13.4	1791	82
6.		Canon RP	Full Frame	26.0	6240	4160	4K/30p	24.3	11.9	2977	85
7.		Fujifilm X-T30	APS-C	26.0	6240	4160	4K/30p	24.1	13.5	1895	83
8.		Leica CL	APS-C	24.1	6014	4014	4K/30p	24.0	13.3	1788	82
9.		Leica M-E Typ 240	Full Frame	23.7	5952	3976	1080/25p	25.2	14.2	2821	94
10.		Leica Q Typ 116	Full Frame	24.0	6000	4000	1080/60p	24.3	12.7	2221	85
11.		Leica S2	Medium Format	37.5	7500	5000	none	23.9	12.5	2224	82
12.		Leica S Typ 006	Medium Format	37.5	7500	5000	none	23.9	12.2	824	76
13.		Leica TL2	APS-C	24.1	6014	4014	4K/30p	23.9	13.3	1753	82
14.		Nikon D3S	Full Frame	12.1	4256	2832	720/24p	23.5	12.0	3253	82
15.		Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
16.		Sony A6100	APS-C	24.0	6000	4000	4K/30p	24.1	13.6	1947	84
17.		Sony A6400	APS-C	24.0	6000	4000	4K/30p	24.0	13.6	1431	83
Note: DXO values in italics represent estimates based on sensor size and age.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. The S1 and the 645D are similar in the sense that both have an optical viewfinder. The latter is useful for getting a clear image for framing even in brightly lit environments. The following table reports on some other key feature differences and similarities of the Leica S1, 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.		Leica S1	optical	n	none / none	none	n	..	0.01/s	n	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 250D	optical	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
6.		Canon RP	2360	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	n	n
7.		Fujifilm X-T30	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	n
8.		Leica CL	2360	Y	3.0 / 1040	fixed	Y	1/8000s	10.0/s	n	n
9.		Leica M-E Typ 240	optical	n	3.0 / 920	fixed	n	1/4000s	3.0/s	n	n
10.		Leica Q Typ 116	3680	n	3.0 / 1040	fixed	Y	1/2000s	10.0/s	n	Y
11.		Leica S2	optical	Y	3.0 / 460	fixed	n	1/4000s	1.5/s	n	n
12.		Leica S Typ 006	optical	Y	3.0 / 922	fixed	n	1/4000s	1.5/s	n	n
13.		Leica TL2	optional	n	3.7 / 1230	fixed	Y	1/4000s	7.0/s	n	n
14.		Nikon D3S	optical	Y	3.0 / 921	fixed	n	1/8000s	11.0/s	n	n
15.		Pentax 645Z	optical	Y	3.2 / 1037	tilting	n	1/4000s	3.0/s	n	n
16.		Sony A6100	1440	n	3.0 / 922	tilting	Y	1/4000s	11.0/s	Y	n
17.		Sony A6400	2359	n	3.0 / 922	tilting	Y	1/4000s	11.0/s	Y	n
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One feature that is present on the 645D, but is missing on the S1 is a top-level LCD. While being, of course, smaller than the rear screen, the control panel conveys some of the essential shooting information and can be convenient for quick and easy settings verification.

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.

The S1 writes its imaging data to external storage, while the 645D uses SDXC 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 Leica S1 Pro 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.		Leica S1	-	- / -	-	-	-	-	-	-	-
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 250D	Y	stereo / mono	Y	-	mini	2.0	Y	-	Y
6.		Canon RP	Y	stereo / mono	Y	Y	micro	2.0	Y	-	Y
7.		Fujifilm X-T30	Y	stereo / mono	Y	-	micro	3.1	Y	-	Y
8.		Leica CL	Y	stereo / mono	-	-	-	-	Y	-	-
9.		Leica M-E Typ 240	Y	mono / -	-	-	-	2.0	-	-	-
10.		Leica Q Typ 116	Y	stereo / mono	-	-	micro	2.0	Y	Y	-
11.		Leica S2	Y	- / -	-	-	mini	2.0	-	-	-
12.		Leica S Typ 006	Y	- / -	-	-	mini	2.0	-	-	-
13.		Leica TL2	Y	stereo / mono	-	-	micro	3.0	Y	-	-
14.		Nikon D3S	Y	stereo / -	-	-	mini	2.0	-	-	-
15.		Pentax 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-
16.		Sony A6100	Y	stereo / mono	Y	-	micro	2.0	Y	Y	Y
17.		Sony A6400	Y	stereo / mono	Y	-	micro	2.0	Y	Y	Y

It is notable that the 645D has a hotshoe, which makes it possible to easily attach optional accessories, such as an external flash gun. The S1 does not feature such an accessory-socket.

Studio photographers will appreciate that the Pentax 645D (unlike the S1) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the S1 and the 645D have been discontinued, but can regularly be found used on ebay. The S1 was replaced by the Leica S2, while the 645D was followed by the Pentax 645Z. Further information on the two cameras (e.g. user guides, manuals), as well as related accessories, can be found on the official Leica and Pentax websites.

Review summary

So what is the bottom line? Is there a clear favorite between the Leica S1 and the Pentax 645D? Which camera is better? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Leica S1 Pro:

• More legacy lens friendly: Can take a broad range of non-native lenses via adapters.
• More prestigious: Has the Leica luxury appeal, which ensures a high resale price.
• More heavily discounted: Has been available for much longer (launched in August 1996).

Reasons to prefer the Pentax 645D:

• More detail: Has more megapixels (39.5 vs 26.4MP), which boosts linear resolution by 25%.
• Easier setting verification: Features a control panel on top to check shooting parameters.
• Rear screen: Has a backside LCD (3.0") for image review and settings control.
• Faster burst: Shoots at higher frequency (1.1 vs 0.01 flaps/sec) to capture the decisive moment.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• More compact: Is smaller (156x117mm vs 339x214mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight (by 1020g or 41 percent) and is thus easier to take along.
• Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
• Better lighting: Features a hotshoe and can thus hold and trigger an external flash gun.
• Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
• More affordable: Was introduced into a lower priced category (54 percent cheaper at launch).
• More modern: Reflects 13 years and 6 months of technical progress since the S1 launch.

If the count of relative strengths (bullet points above) is taken as a measure, the 645D is the clear winner of the contest (12 : 3 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 wildlife photographer will view the differences between cameras in a way that diverges from the perspective of a family photog, and a person interested in architecture has distinct needs from a sports 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 Leica S1 and the Pentax 645D place the cameras among the top in their class? Find out in the latest Best Mirrorless Interchangeable Lens Camera and Best DSLR Camera listings whether the two cameras rank among the cream of the crop.

In any case, while the comparison of technical specifications can provide a useful overview of the capabilities of different cameras, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the S1 or the 645D. 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 where reviews by experts come in. 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	Street Price
1.		Leica S1	..	..	..	..	..	..	Aug 1996	EUR 21 499	ebay.com
2.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	EUR 9 995	ebay.com
3.		Canon 1D Mark IV	5/5	..	..	89/100	..	..	Oct 2009	EUR 4 699	ebay.com
4.		Canon 1D X	5/5	..	..	..	4.5/5	4.5/5	Oct 2011	EUR 6 299	ebay.com
5.		Canon 250D	4/5	o	4.5/5	79/100	4/5	4/5	Apr 2019	EUR 549	amazon.com
6.		Canon RP	4/5	+	4/5	..	4.5/5	4/5	Feb 2019	EUR 1 499	amazon.com
7.		Fujifilm X-T30	5/5	+ +	5/5	84/100	4.5/5	4.5/5	Feb 2019	EUR 999	ebay.com
8.		Leica CL	..	..	4.2/5	..	..	4/5	Nov 2017	EUR 2 490	ebay.com
9.		Leica M-E Typ 240	..	..	..	..	..	..	Jun 2019	EUR 3 949	ebay.com
10.		Leica Q Typ 116	5/5	..	..	80/100	4.5/5	4.5/5	Jun 2015	EUR 3 999	ebay.com
11.		Leica S2	..	..	..	..	..	..	Sep 2008	EUR 18 599	ebay.com
12.		Leica S Typ 006	..	..	..	..	..	..	Sep 2012	EUR 19 499	ebay.com
13.		Leica TL2	3.5/5	..	3/5	..	4/5	4/5	Jul 2017	EUR 1 949	ebay.com
14.		Nikon D3S	5/5	..	..	89/100	4.5/5	5/5	Oct 2009	EUR 4 999	ebay.com
15.		Pentax 645Z	5/5	..	3.5/5	..	4.5/5	5/5	Apr 2014	EUR 6 999	ebay.com
16.		Sony A6100	..	..	4/5	82/100	4/5	5/5	Aug 2019	EUR 899	ebay.com
17.		Sony A6400	4/5	+	4/5	85/100	4.5/5	4/5	Jan 2019	EUR 1 049	amazon.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The review scores listed above should be treated with care, though. The ratings are only valid when referring to cameras in the same category and of the same age. Thus, a score needs to be put into the context of the launch date and the launch price of the camera, and rating-comparisons among cameras that span long time periods or concern very differently equipped models make little sense. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

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Other camera comparisons

Did this review help to inform your camera decision process? In case you are interested in seeing how other cameras pair up, just make a corresponding selection in the search boxes below. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.

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