APSC or full-frame camera and lens: what is the better choice?



Since 2016, Pentaxists have had two families of SLR cameras at their disposal: one in APS-C sensor format, the other in "Full Frame" format, i.e. with a 24 x 36 sensor. What are the best criteria for choosing one and why?
In fact, there is no single choice that applies to everyone. The choice between one or the other of the two formats only answers particular needs.



Full frame sensor

This is the traditional 35 mm format for film photography, which is the most widespread. Although, of course, there have been and still are other film formats (120 / 220, for example). In digital photography, this format has also been implemented by all major camera manufacturers. And, although almost all types of photos are available with both sensor formats, some of them could guide the choice.

Why choose the 24 x 36 sensor
(full frame camera and full frame lenses)?

This format seems to be the preferred choice when you need to :

- to print photos in large dimensions: sensors with more pixels generally allow larger enlargements

- excellent definition: even if it is necessary to modulate the statement, FF sensors (full format) often offer a better definition

- to play with the depth of field: FF sensors, depending on the conditions, allow for more blurred background (bokeh) than APS-C sensors

- a wider field of view

- clear and precise viewfinder: until now, full-frame cameras have had a better and more comfortable viewfinder than their APS-C counterparts.

However, Pentax has made progress in this area, especially with the introduction of the new flagship APS-C camera, the PENTAX K-3 mark III, which features a completely new prism, which has greatly improved the traditional viewfinder of APS-C cameras.

- Large-aperture lenses: in reality, it is the full-frame lenses that offer the largest apertures; these are generally smaller on dedicated APS-C lenses.


Areas where full frame should be chosen

Based on these findings, it can be deduced that certain areas of photography are "favoured" by full-frame lenses:

  • Portraiture and, above all, studio portraiture
  • Landscape photography
  • Architectural photography, especially with specialised lenses (tilt and shift) designed for this format.

However, this does not mean that all other areas are destined for APS-C format!




The APS-C sensor

It is sometimes referred to as "half format" or small format. While a full-frame sensor has an approximate size of 24 mm x 36 mm, an APS-C sensor has an approximate size of 15.7 mm x 23.6 mm. This is the sensor that first appeared in SLR cameras, mainly for technological and cost reasons: designing a 24 x 36 sensor is much more difficult and considerably more expensive.


When to choose APS-C sensor?

To determine when to buy an APS-C format camera, you have to take into account its particular characteristics. The angle of the photographed field is narrower for the same focal length. For example, a 50 mm lens (for example the HD Pentax-D FA* 50mm F1.4 SDM AW) covers a horizontal field of 40° on a 24 x 36 sensor camera whereas this field is 27° on an APS-C camera.

The field of view is therefore much narrower, corresponding approximately to what would be obtained on a 24 x 36 camera with a 75 mm focal length lens. This difference represents the "conversion coefficient", whose value is close to 1.5. As the focal lengths of the lenses are always given in reference to the traditional 35 mm format (24 x 36), it should be considered that, on an APS-C camera, they correspond to focal lengths 1.5 times longer.

This format seems to be the best choice when:

- The weight of the camera/lens assembly is an important argument for the photographer: this assembly is notably lighter in APS-C than in full format. For example, the APS-C DA* 50-135 mm f/2.8 zoom lens is roughly equivalent to the D-FA 70-200 mm f/2.8 zoom lens, which was designed primarily for the 24 × 36 format, using the conversion factor mentioned above. While the former weighs 685g without a lens hood (and costs around 1199 €), the latter weighs around 1.755kg (also without a lens hood), and costs 2099 €. Yet the angle of view is similar. As for the bare bodies, the APSC PENTAX K-3 Mark III weighs 820 g with battery and SD card, while the full-frame PENTAX K-1 Mark II weighs 1010 g under the same conditions.

- You need more depth of field: an aperture of 2.8 on an APS-C does not induce the same depth of field as in 24×36 format: it corresponds, in fact, to an aperture of 4.2.

- We need to frame more tightly: this is the result of the conversion coefficient mentioned above. Shooting with a PENTAX DA* 300 mm on a PENTAX K-3 Mark III would be equivalent to shooting with a 450 mm on a PENTAX K-1 MARK II.

- Lighter" image files are desired: The DNG or PEF files generated by a PENTAX K-1 MARK II (36.4 megapixel FF sensor) are around and sometimes exceed 50 megabytes. A PENTAX K-3 MARK III (25.73 megapixel sensor) is about 10 megabytes lighter. This means that the same SD card can store more images and they also take up less space on the computer's hard drive.

APS-C focus areas

The above considerations lead us to believe that APS-C is particularly suitable for :

- Wildlife photography: the same lens seems to have a longer focal length (x1.5) and the subject can therefore be photographed from further away for the same magnification

- Proxi-photography, for the same reasons. It is a little different in true macro photography (magnification of 1:1 or greater) where the focal length is mainly used to set the minimum focusing distance for a given magnification.

- All areas or situations where the subject is far away and therefore the focal length conversion factor plays an important role.In street photography, for example, it may be desirable to move away from the subject.

But in many areas of photography, the sensor format is not a determining factor, either in itself or in the quality of the images produced.



To conclude

With the right tools for the job (mainly lenses), all areas of photography are accessible to both APS-C and FF sensors. The choice of one or the other depends more on personal criteria (budget - although this is becoming more and more relative! -) rather than technological criteria. However, manufacturers are doing their best to offer photographers ever more practical and efficient 'tools'.

Experienced photographers who wish to continue to equip themselves with Pentax cameras, know very well what they can choose:

in full format, the Pentax K-1 mark II, in APS-C the K-3 mark III. The more affluent and/or demanding will also consider the medium format 645Z, but that's another world. As for beginners who want to buy Pentax equipment :

- If they want a full-frame camera, the choice will necessarily turn to the K-1 mark II (the only one available in new equipment), and, in second-hand equipment, either to the same model or to a K-1 first of the name..

- If they go for a new APS-C camera, the main argument for choice could be the available budget. A relatively large budget will lead to a K-3 mark III, a must-have among SLRs of all brands.

More modest means will make you choose the PENTAX K-70, which fully satisfies those who already own it. In second-hand equipment, the choice remains quite vast (K-S2, K-3, K-3 II, KP to mention only the latest models) being specified however that a considerable technological leap was made with the K-3 mark III.