[GUB]

Went out for a shoot with my sister and her K10 (I think) and challenged her to a bokeh shot of this thread sticking out of a moss clad structure. We were both using a Pentax A 50mm 2.8 macro set wide open. We ended up both taking the shot from a very similar angle. Hers is the more yellowy shot. I was thinking the full frame with its shallow dof would have the smoother bokeh but the apsc shot background appears smoother. Is it just that the apsc has cropped to a smaller simpler area in the background. Or has it performed like the telescopic lens effect where the increase in blur increases exponentially compared to a shorter focal length ?

Attached Images

   

[D1N0]

It is because of perspective. The 50 on aps-c equivalent to a 75mm lens on Full frame, so you are further away from the subject if you want the same field of view.

[david94903]

Interesting. Nice examples.

[Sandy Hancock]

I'm pretty certain the top shot is NOT wide open. The OoF highlights are hexagonal.

[Not a Number]

Interesting experiment indeed.

Consider that the K10D has a 10Mp CCD sensor vs the 36Mp (16 crop mode) CMOS.

Further comparisons that would be interesting: Use a tripod, swapping the cameras so the distance to the subject is the same. Unfortunately the K10D does not have a sensor plane indicator marking on the body.so you can't precisely adjust the distance but measuring from the flange should work. Shoot the K-1 in both FF and crop mode. Along with comparing the FF, K-1 crop and K10D images crop the FF image in PP.

Of course interesting doesn't necessarily mean fun, which is a major point of photography for the enthusiast

[UncleVanya]

Given the same framing AND the same lens and aperture your larger sensor will give MORE depth of field contrary to the expectations of most people. If you used two different lenses and attempted to maintain distance to the subject with the same framing then the ff would have shallower dof.

The subject is well covered in this part 3 of a series on dof: Depth of Field, Part III: The Myths | B&H Explora

However, as Sandy said, there appear to be some hexagonal highlights in the full frame shot. Is it possible this shot wasn't wide open? Were you both using the same copy of the lens? Does the aperture operate with snappy quick results? Can you post examples that have EXIF intact?

---------- Post added 12-24-18 at 09:23 AM ----------

As an aside, I prefer the k10d shot (bottom) at this resolution.

[victormeldrew]

The fact that you can have such a shallow DoF from so much further away is why FF is better. The top one doesn't even look fully wide.

[Lowell Goudge]

What you have really discovered is the impact of relative magnification of subject to background. Or as some put it the perspective.

With the crop sensor, you back away from the subject, and as a result the background is larger in relative terms to foreground.

For bokeh it is more about controlling the background and subject to background separation, then just having a fast lens.

[GUB]

I'm pretty certain the top shot is NOT wide open. The OoF highlights are hexagonal.

I see what you are saying - there does seem to be a hex element in the bokeh. I was using the manual apertures rather than the A setting to keep the liveview lit up. Maybe I hadn't quite clicked it home. Dang - going to have to do a test.

[GUB]

Interesting experiment indeed.

Consider that the K10D has a 10Mp CCD sensor vs the 36Mp (16 crop mode) CMOS.

Further comparisons that would be interesting: Use a tripod, swapping the cameras so the distance to the subject is the same. Unfortunately the K10D does not have a sensor plane indicator marking on the body.so you can't precisely adjust the distance but measuring from the flange should work. Shoot the K-1 in both FF and crop mode. Along with comparing the FF, K-1 crop and K10D images crop the FF image in PP.

Of course interesting doesn't necessarily mean fun, which is a major point of photography for the enthusiast

I think you have it wrong way round - rather than have the cameras at the same distance the apsc needs to be 50% further away. This is why you can't just crop the centre of the full frame to represent the apsc. The pictures above were not an experiment , they were coincidence. For me to experiment is fun and a way of teaching myself. Posting here just adds to the fun.

[Dartmoor Dave]

The K10D has got an optical AA filter and the K-1 doesn't, so I wonder if that might have something to do with it too (although it'll mostly be the difference in perspective and possibly aperture as mentioned above). I suppose we'd need to know about any sharpening used in post.

It's fascinating to see the two shots together, and I'd love to see more from the same outing with such different cameras.

[GUB]

The K10D has got an optical AA filter and the K-1 doesn't, so I wonder if that might have something to do with it too (although it'll mostly be the difference in perspective and possibly aperture as mentioned above). I suppose we'd need to know about any sharpening used in post.

It's fascinating to see the two shots together, and I'd love to see more from the same outing with such different cameras.

My sis's shot will be excamera jpg while mine was full edit with smart sharpening. Smart sharpening will not have sharpened the bokeh at all. I will do a similar comparison with my K01 and K1 but Christmas has got in the road. (Christmas morning here at the mo) So merry Christmas and see you on the other side.!

[Not a Number]

I think you have it wrong way round - rather than have the cameras at the same distance the apsc needs to be 50% further away. This is why you can't just crop the centre of the full frame to represent the apsc.

Try it both ways, I'd be interested to see the results. I don't have a K-1/ii

[repaap]

I see what you are saying - there does seem to be a hex element in the bokeh. I was using the manual apertures rather than the A setting to keep the liveview lit up. Maybe I hadn't quite clicked it home. Dang - going to have to do a test.

I do agree with Sandy, your K-1 shot has clear hexagon just bottom right from bolt. that would say two click atleast maybe even more. do it wide open and you’ll see some bokeh. oh and fot LV staying lit up, change settings for that

also you see main advantage from FF vs crop/ disadvantage. at same distance there is more things in picture, so you can see more of what is around the subject.

[ZombieArmy]

There's no hexagons. If you look closely it's just other bokeh "balls" intersecting to make it look like that. All the bokeh is perfectly circular.