Canon SL3 vs Pentax 645D

The Canon EOS Rebel SL3 (called Canon 250D in some regions) and the Pentax 645D are two digital cameras that were announced, respectively, in April 2019 and March 2010. Both are DSLR (Digital Single Lens Reflex) cameras that are based on an APS-C (SL3) and a medium format (645D) sensor. The Canon has a resolution of 24 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

Canon SL3		Pentax 645D
Digital single lens reflex		Digital single lens reflex
Canon EF mount lenses		Pentax 645 mount lenses
24 MP – APS-C sensor		39.5 MP – Medium Format sensor
4K/25p Video		no Video
ISO 100-25,600 (100 - 51,200)		ISO 100-1,600
Optical viewfinder		Optical viewfinder
3.0" LCD – 1040k dots		3.0" LCD – 921k dots
Swivel touchscreen		Fixed screen (not touch-sensitive)
5 shutter flaps per second		1.1 shutter flaps per second
not weather sealed		Weathersealed body
1070 shots per battery charge		800 shots per battery charge
122 x 93 x 70 mm, 449 g		156 x 117 x 119 mm, 1480 g

Check SL3 price at
amazon.com
Check 645D offers at
ebay.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Canon EOS Rebel SL3 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 Canon SL3 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 dimensions are rounded to the nearest millimeter.

The SL3 can be obtained in two different colors (black, white), 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 (61 percent) than the Canon SL3. Moreover, the 645D is substantially heavier (230 percent) than the SL3. It is noteworthy in this context that the 645D is splash and dust-proof, while the SL3 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.

Concerning battery life, the SL3 gets 1070 shots out of its Canon LP-E17 battery, while the 645D can take 800 images on a single charge of its Pentax D-LI90 power pack.

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 (USD)	Street Price
1.		Canon SL3	122 mm	93 mm	70 mm	449 g	1070	n	Apr 2019	599	amazon.com
2.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	9,995	ebay.com
3.		Canon T8i	131 mm	103 mm	76 mm	515 g	800	n	Feb 2020	749	ebay.com
4.		Canon M50 Mark II	116 mm	88 mm	59 mm	387 g	305	n	Oct 2020	599	ebay.com
5.		Canon M50	116 mm	88 mm	59 mm	390 g	235	n	Feb 2018	779	ebay.com
6.		Canon T7	129 mm	101 mm	78 mm	475 g	500	n	Feb 2018	449	amazon.com
7.		Canon 77D	131 mm	100 mm	76 mm	540 g	600	n	Feb 2017	899	ebay.com
8.		Canon SL2	122 mm	93 mm	70 mm	453 g	650	n	Jun 2017	549	ebay.com
9.		Canon T7i	131 mm	100 mm	76 mm	532 g	600	n	Feb 2017	749	ebay.com
10.		Canon T6s	132 mm	101 mm	78 mm	565 g	440	n	Feb 2015	649	ebay.com
11.		Canon SL1	117 mm	91 mm	69 mm	407 g	380	n	Mar 2013	549	ebay.com
12.		Canon 1D X	158 mm	168 mm	83 mm	1551 g	1120	Y	Oct 2011	6,799	ebay.com
13.		Canon T2i	129 mm	98 mm	62 mm	530 g	440	n	Feb 2010	699	ebay.com
14.		Canon 1D Mark IV	156 mm	157 mm	80 mm	1230 g	1500	Y	Oct 2009	4,999	ebay.com
15.		Leica S Typ 006	160 mm	120 mm	80 mm	1260 g	..	Y	Sep 2012	21,950	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

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 SL3 was launched at a markedly lower price (by 94 percent) than the 645D, 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 size of the sensor inside a digital camera is one of the key determinants of image quality. A large sensor will tend to have larger individual pixels that provide better low-light sensitivity, wider dynamic range, and richer color-depth than smaller pixel-units in a sensor of the same technological generation. Further, a large sensor camera will give the photographer additional creative options when using shallow depth-of-field to isolate a subject from its background. On the downside, larger sensors tend to be associated with larger, more expensive camera bodies and lenses.

Of the two cameras under consideration, the Canon SL3 features an APS-C sensor and the Pentax 645D a medium format sensor. The sensor area in the 645D is 337 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.6 and 0.79. The sensor in the SL3 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 SL3 (24MP), but the 645D nevertheless has larger individual pixels (pixel pitch of 6.06μm versus 3.72μm for the SL3) due to its larger sensor. However, the SL3 is a much more recent model (by 9 years and 1 month) 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 the 645D has no anti-alias filter installed, so that it can capture all the detail its 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 Canon SL3 are 30 x 20 inches or 76.2 x 50.8 cm for good quality, 24 x 16 inches or 61 x 40.6 cm for very good quality, and 20 x 13.3 inches or 50.8 x 33.9 cm for excellent quality prints.

The SL3 has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.

The Canon EOS Rebel SL3 has a native sensitivity range from ISO 100 to ISO 25600, which can be extended to ISO 100-51200. The corresponding ISO settings for the Pentax 645D are ISO 100 to ISO 1600 (no boost).

In terms of underlying technology, the SL3 is build around a CMOS sensor, while the 645D uses a CCD imager. 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 is based on lab testing and assigns an overall score to each camera sensor, as well as ratings for dynamic range ("DXO Landscape"), color depth ("DXO Portrait"), and low-light sensitivity ("DXO Sports"). 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.		Canon SL3	APS-C	24.0	6000	4000	4K/25p	23.9	13.4	1791	82
2.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
3.		Canon T8i	APS-C	24.0	6000	4000	4K/24p	24.0	13.5	1873	83
4.		Canon M50 Mark II	APS-C	24.0	6000	4000	4K/24p	24.0	13.6	1939	83
5.		Canon M50	APS-C	24.0	6000	4000	4K/24p	23.8	13.3	1684	81
6.		Canon T7	APS-C	24.0	6000	4000	1080/30p	23.8	13.3	1684	81
7.		Canon 77D	APS-C	24.0	6000	4000	1080/60p	23.6	13.3	971	78
8.		Canon SL2	APS-C	24.0	6000	4000	1080/60p	23.6	13.4	1041	79
9.		Canon T7i	APS-C	24.0	6000	4000	1080/60p	23.7	13.1	1586	80
10.		Canon T6s	APS-C	24.0	6000	4000	1080/30p	22.6	12.0	915	70
11.		Canon SL1	APS-C	17.9	5184	3456	1080/30p	21.8	11.3	843	63
12.		Canon 1D X	Full Frame	17.9	5184	3456	1080/30p	23.8	11.8	2786	82
13.		Canon T2i	APS-C	17.9	5184	3456	1080/30p	22.1	11.5	784	66
14.		Canon 1D Mark IV	APS-H	16.0	4896	3264	1080/30p	22.8	12.0	1320	74
15.		Leica S Typ 006	Medium Format	37.5	7500	5000	none	23.9	12.2	824	76
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 SL3 indeed provides movie recording capabilities, while the 645D does not. The highest resolution format that the SL3 can use is 4K/25p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a variety of features. The SL3 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 viewfinder in the 645D offers a wider field of view (98%) than the one in the SL3 (95%), so that a larger proportion of the captured image is visible in the finder. In addition, the viewfinder of the 645D has a higher magnification (0.78x vs 0.54x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The adjacent table lists some of the other core features of the Canon SL3 and Pentax 645D along with similar information for a selection of comparators.

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.		Canon SL3	optical	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
2.		Pentax 645D	optical	Y	3.0 / 921	fixed	n	1/4000s	1.1/s	n	n
3.		Canon T8i	optical	n	3.0 / 1040	swivel	Y	1/4000s	7.5/s	Y	n
4.		Canon M50 Mark II	2360	n	3.0 / 1040	swivel	Y	1/4000s	10.0/s	Y	n
5.		Canon M50	2360	n	3.0 / 1040	swivel	Y	1/4000s	10.0/s	Y	n
6.		Canon T7	optical	n	3.0 / 920	fixed	n	1/4000s	3.0/s	Y	n
7.		Canon 77D	optical	Y	3.0 / 1040	swivel	Y	1/4000s	6.0/s	Y	n
8.		Canon SL2	optical	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
9.		Canon T7i	optical	n	3.0 / 1040	swivel	Y	1/4000s	6.0/s	Y	n
10.		Canon T6s	optical	Y	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
11.		Canon SL1	optical	n	3.0 / 1040	fixed	Y	1/4000s	4.9/s	Y	n
12.		Canon 1D X	optical	Y	3.2 / 1040	fixed	n	1/8000s	14.0/s	n	n
13.		Canon T2i	optical	n	3.0 / 1040	fixed	n	1/4000s	3.7/s	Y	n
14.		Canon 1D Mark IV	optical	Y	3.0 / 920	fixed	n	1/8000s	10.0/s	n	n
15.		Leica S Typ 006	optical	Y	3.0 / 922	fixed	n	1/4000s	1.5/s	n	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 SL3 has one, while the 645D does not. While the built-in flash of the SL3 is not very powerful, it can at times be useful as a fill-in light.

The Canon SL3 and the Pentax 645D both have 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 SL3 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 SL3 only has one slot. The SL3 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 Canon EOS Rebel SL3 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.		Canon SL3	Y	stereo / mono	Y	-	mini	2.0	Y	-	Y
2.		Pentax 645D	Y	stereo / -	-	-	-	2.0	-	-	-
3.		Canon T8i	Y	stereo / mono	Y	-	mini	2.0	Y	-	Y
4.		Canon M50 Mark II	Y	stereo / mono	Y	-	micro	2.0	Y	-	Y
5.		Canon M50	Y	stereo / mono	Y	-	micro	2.0	Y	-	Y
6.		Canon T7	Y	mono / mono	-	-	mini	2.0	Y	Y	-
7.		Canon 77D	Y	stereo / mono	Y	-	mini	2.0	Y	Y	Y
8.		Canon SL2	Y	stereo / mono	Y	-	mini	2.0	Y	Y	Y
9.		Canon T7i	Y	stereo / mono	Y	-	mini	2.0	Y	Y	Y
10.		Canon T6s	Y	stereo / mono	Y	-	mini	2.0	Y	Y	-
11.		Canon SL1	Y	mono / mono	Y	-	mini	2.0	-	-	-
12.		Canon 1D X	Y	mono / -	Y	-	mini	2.0	-	-	-
13.		Canon T2i	Y	stereo / -	Y	-	mini	2.0	-	-	-
14.		Canon 1D Mark IV	Y	stereo / -	Y	-	mini	2.0	-	-	-
15.		Leica S Typ 006	Y	- / -	-	-	mini	2.0	-	-	-
16.		Nikon D3S	Y	stereo / -	-	-	mini	2.0	-	-	-
17.		Pentax 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-

It is notable that the SL3 offers wifi support, while the 645D does not. Wifi can be a very convenient means to transfer image data to an off-camera location.

Studio photographers will appreciate that the Pentax 645D (unlike the SL3) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

The SL3 is a recent model that features in the current product line-up of Canon. In contrast, the 645D has been discontinued (but can be found pre-owned on ebay). As a replacement in the same line of cameras, the 645D was succeeded by the Pentax 645Z. Further information on the features and operation of the SL3 and 645D can be found, respectively, in the Canon SL3 Manual (free pdf) or the online Pentax 645D Manual.

Review summary

So how do things add up? Is there a clear favorite between the Canon SL3 and the Pentax 645D? Which camera is better? Below is a summary of the relative strengths of each of the two contestants.

Advantages of the Canon EOS Rebel SL3:

• Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
• Broader imaging potential: Can record not only still images but also 4K/25p movies.
• Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
• More detailed LCD: Has a higher resolution rear screen (1040k vs 921k dots).
• More flexible LCD: Has a swivel screen for odd-angle shots in portrait or landscape orientation.
• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• More selfie-friendly: Has an articulated screen that can be turned to be front-facing.
• Faster burst: Shoots at higher frequency (5 vs 1.1 flaps/sec) to capture the decisive moment.
• More compact: Is smaller (122x93mm vs 156x117mm) and thus needs less room in the bag.
• Less heavy: Is lighter (by 1031g or 70 percent) and hence easier to carry around.
• Longer lasting: Can take more shots (1070 versus 800) on a single battery charge.
• Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
• Easier file upload: Has wifi built in for automatic backup or image transfer to the web.
• Easier wireless transfer: Supports Bluetooth for image sharing without cables.
• Faster buffer clearing: Has an SD card interface that supports the UHS-I standard.
• More affordable: Was introduced into a lower priced category (94 percent cheaper at launch).
• More modern: Reflects 9 years and 1 month of technical progress since the 645D launch.

Arguments in favor of the Pentax 645D:

• More detail: Has more megapixels (39.5 vs 24MP), which boosts linear resolution by 26%.
• Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
• More complete view: Has a viewfinder with a larger field of view (98% vs 95%).
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.78x vs 0.54x).
• Easier setting verification: Features a control panel on top to check shooting parameters.
• 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 number of relative strengths (bullet points above) is taken as a guide, the SL3 is the clear winner of the match-up (17 : 9 points). However, the relevance of individual strengths will vary across photographers, so that you might want to apply your own weighing scheme to the summary points when reflecting and deciding 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 Canon SL3 and the Pentax 645D place the cameras among the top in their class? Find out in the latest Best DSLR Camera listing whether the two cameras rank among the cream of the crop.

In any case, while the comparison of the spec-sheets of cameras can offer a general idea of their imaging potential, it says little about, for example, the shooting experience and imaging performance of the SL3 and the 645D in practical situations. 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 adjacent summary-table relays the overall verdicts of several of the most popular camera 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.		Canon SL3	4/5	o	4.5/5	79/100	4/5	4/5	Apr 2019	599	amazon.com
2.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	9,995	ebay.com
3.		Canon T8i	4.5/5	+	3/5	80/100	4/5	3.5/5	Feb 2020	749	ebay.com
4.		Canon M50 Mark II	4/5	..	4/5	..	4.5/5	3.5/5	Oct 2020	599	ebay.com
5.		Canon M50	..	+	4/5	79/100	..	3.5/5	Feb 2018	779	ebay.com
6.		Canon T7	..	o	3.5/5	..	3.5/5	3.5/5	Feb 2018	449	amazon.com
7.		Canon 77D	4.5/5	..	4/5	82/100	4.5/5	4/5	Feb 2017	899	ebay.com
8.		Canon SL2	4/5	+ +	4/5	78/100	4.5/5	4.5/5	Jun 2017	549	ebay.com
9.		Canon T7i	4.5/5	..	3.5/5	80/100	4.5/5	4/5	Feb 2017	749	ebay.com
10.		Canon T6s	5/5	+	..	77/100	4.5/5	4.5/5	Feb 2015	649	ebay.com
11.		Canon SL1	4/5	+	..	78/100	4/5	4/5	Mar 2013	549	ebay.com
12.		Canon 1D X	5/5	..	..	..	4.5/5	4.5/5	Oct 2011	6,799	ebay.com
13.		Canon T2i	..	+ +	..	77/100	4/5	4.5/5	Feb 2010	699	ebay.com
14.		Canon 1D Mark IV	5/5	..	..	89/100	..	..	Oct 2009	4,999	ebay.com
15.		Leica S Typ 006	..	..	..	..	..	..	Sep 2012	21,950	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.

The above review scores should be interpreted 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 comparing ratings of very distinct cameras or ones that are far apart in terms of their release date have little meaning. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

Check SL3 price at
amazon.com
Check 645D offers at
ebay.com

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. Alternatively, you can follow any of the listed hyperlinks for comparisons that others found interesting.

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