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Pentax

645Z

51MP medium format DSLR that made digital MF accessible — still prized for landscape and studio.

$8,499

Launch price

Released Apr 2014

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vs

Pentax

K-3 Mark III

APS-C DSLR flagship with optical viewfinder and weather sealing.

$1,999

Launch price

Released Apr 2021

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K-3 Mark III is 7 years newer.

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Wins

2categories

645Z

★ Wildlife★ Landscape

Wins

1categories

K-3 Mark III

★ Wildlife★ Travel

15 categories tied

Which would you choose?

TL;DR — Key differences

645Z wins 2 categories·K-3 Mark III wins 1 categories
  • BK-3 Mark III has lower Weight (520 g vs 1470 g)
  • A645Z has higher Resolution (51.4 MP vs 25.7 MP)
  • A645Z has lower ISO min (native) (64 vs 100)

Key specs at a glance

645ZK-3 Mark III
Resolution51.4 MP25.7 MP
Sensor43.8 × 32.8 mmAPS-C
ISO max25,60025,600
Burst20 fps20 fps
4K60 fps60 fps
IBIS7-stop7-stop
Weight1470 g520 g
Battery640 shots640 shots

Size and weight, to scale

645Z

156 × 117 × 123 mm

1470 g (3.24 lb / 51.85 oz)

Credit card shown to scale as a size reference (ISO 7810, 85.6 × 54 mm)

Credit card

85.6 × 54 mm

for scale

K-3 Mark III

138 × 98 × 88 mm

520 g (1.15 lb / 18.34 oz)

645Z is 18mm wider, 19mm taller, and 35mm thicker than K-3 Mark III.

645Z is 950 g heavier than K-3 Mark III.

Depth (front-to-back): 123mm 645Z · 88mm K-3 Mark III

Sensor size, to scale

645Z

43.8 × 32.8 mm · Medium Format

1437 mm² area

K-3 Mark III

23.5 × 15.6 mm · APS-C

367 mm² area

3.9× larger sensor area = shallower depth of field and better low-light performance.

Lens ecosystem

Native lens selection

645Z: mount data unavailable

K-3 Mark III

✓ more lenses

Pentax K

70+

native lenses available

30 first-party40 third-party

Counts include current first-party and major third-party native autofocus lenses.

Use-case scoring

Which one for what?

Algorithmic scores from verified specs · 10 = best in class

Use case645ZK-3 Mark III
Portrait
6.0Good
6.5Good✓ wins
Sports & Action
6.5Good
6.5Good
Video & Hybrid
6.0Good
6.0Good
Landscape
8.0Excellent✓ wins
5.0Fair
Travel
5.5Fair
8.5Excellent✓ wins
Wildlife
9.0Excellent
10.0Excellent✓ wins
Vlogging
5.5Fair
7.0Good✓ wins

Why pick one over the other

Reasons to choose

645Z

  • Dimensions (W×H×D mm)

    Adds 156, 117, 123

  • Resolution

    51.4 MP vs 25.7 MP — higher is better

  • AA filter

    Only 645Z supports it

  • ISO min (native)

    64 vs 100 — lower is better

Reasons to choose

K-3 Mark III

  • Dimensions (W×H×D mm)

    Adds 138, 98, 88

  • Weight

    520 g vs 1470 g — lower is better

Both cameras share

  • ✓ISO max (native) — Both 25,600
  • ✓AF points / zones — Both 101
  • ✓AF frame coverage — Both 100 %
  • ✓Eye AF — Both support eye af
  • ✓Animal / bird AF — Both support animal / bird af
  • ✓Burst (mechanical) — Both 8 fps

Pros & cons at a glance

Editorially curated highlights and trade-offs.

645Z

Pros

  • ✓51MP medium format
  • ✓CMOS sensor
  • ✓Pentax color
  • ✓Relatively affordable MF

Cons

  • –Huge body
  • –Slow operation
  • –Limited lens line vs Hasselblad

K-3 Mark III

Pros

  • ✓Optical viewfinder
  • ✓Weather sealed
  • ✓IBIS in DSLR

Cons

  • –DSLR system declining
  • –APS-C
  • –Limited video

Decided which one is right for you?

Compare live prices for the 645Z and K-3 Mark III at major authorized retailers.

Pentax 645Z

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Pentax K-3 Mark III

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Full specifications

✓ = category winner

645Z
K-3 Mark III
Resolution
51.4 MP✓2× more
25.7 MP
Sensor type
Medium Format CMOS
APS-C CMOS
Sensor size
43.8 × 32.8 mm
23.5 × 15.6 mm
AA filter
Yes
No
645Z
K-3 Mark III
Processor
Image processor
Image processor
645Z
K-3 Mark III
ISO min (native)
64✓−36 less
100
ISO max (native)
25,600
25,600
ISO max (expanded)
102,400
102,400
645Z
K-3 Mark III
Shutter type
Mechanical + Electronic
Mechanical + Electronic
Max mechanical speed
1/8000 sec
1/8000 sec
Max electronic speed
1/16000 sec
1/16000 sec

Frequently asked

Quick answers generated from verified specs.

Which is better for landscape, 645Z or K-3 Mark III?

645Z scores 8.0/10 versus 5.0/10 for K-3 Mark III — 51.4MP — massive detail for large prints.

What's the resolution difference between the 645Z and K-3 Mark III?

645Z is 51.4 MP and K-3 Mark III is 25.7 MP, so the 645Z captures more detail for cropping and large prints.

Do the 645Z and K-3 Mark III have in-body image stabilization?

645Z has 7-stop in-body image stabilization, while K-3 Mark III has 7-stop in-body image stabilization.

Which shoots faster bursts — the 645Z or the K-3 Mark III?

645Z reaches 20 fps electronic. K-3 Mark III reaches 20 fps electronic.

What's the weight difference between the 645Z and K-3 Mark III?

645Z weighs 1470 g and K-3 Mark III weighs 520 g, so the K-3 Mark III is 950 g lighter.

Do the 645Z and K-3 Mark III record 4K video?

645Z: 4K up to 60p. K-3 Mark III: 4K up to 60p.

Are the 645Z and K-3 Mark III weather sealed?

645Z: Yes. K-3 Mark III: Yes.

Which has better battery life?

Rated battery life is 640 shots (CIPA) for the 645Z and 640 shots for the K-3 Mark III, giving the K-3 Mark III the edge.

How much does each cost?

645Z launched at $8,499 and K-3 Mark III at $1,999. The K-3 Mark III is $6,500 less.

Can't decide between two? Compare a third camera.

Add any camera to get a three-way 645Z vs K-3 Mark III vs X comparison.

Specs sourced from manufacturer data. Use-case scores algorithmically derived. Last reviewed June 2026.