Q3 Crop Modes and Equivalent Depths of Field Question

[Le Chef]

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Instead of discussing DOF and AOV why aren't people simply taking photographs? Does it make a blind bit of difference if your lens is technically 24.7 vs 28.0 if you're not shooting images?

Maybe we need a geometry forum so people can obsess about protractors and trigonometry and leave the photographic forums to photographers.

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[thegobi]

15 hours ago, jaapv said:

There is more to photography than shallow DOF which is regularity used to camouflage poor composition.

Absolutely this. The current fad for tiny f-numbers, razor thin DOF and bokeh (which now seems to just mean how out of focus the background is) seems everywhere. Is it a marketing thing? I don’t know…

One of the reasons I like using M43 cameras: you think differently about aperture and DOF 😉

 

[mca]

On 1/4/2024 at 10:12 AM, Qwertynm said:

Well, have you actually read it tough? The consensus was that a 90mm crop out of the Q3 looks nothing like a real 90 at f/2.8 in terms of depth of field but can be exactly the same in terms of field of view. The video and link you have posted are helpful for those still not getting it but I think many knowledgeable people already replied and actually DO get it, contrary to what you proclaim. 

I did read the topic yes and there was a smiley at the end of my first sentence, not criticizing anyone really! I just wanted to add some help for those few who were having trouble understanding the difference between the two approaches by showing a practical simple example. 

[Dr. G]

On 1/10/2024 at 3:33 PM, jaapv said:

There is more to photography than shallow DOF which is regularity used to camouflage poor composition. The original Leica aperture was 5 cm/3.5. 50/2.8 was the fast lens. As for the frameline system, users that come from an M prefer it in general. There are quite a few reasons that I don’t want a Q, but these are not part of them. 

I agree with this, but here's a specific scenario not related to shallow DOF...

If I shoot something close up at f/5.6 with a 50mm lens and can shoot at roughly f/3.2 in crop mode to 50mm on the Q3, I would still get an image that looks like it was shot closer to f/5.6 from a depth of field standpoint, but still get the advantages of f/3.2 light gathering.  In this specific case I'd be using crop mode for more depth of field without the light loss penalty.  

[jaapv]

Yes, that is correct The lens speed remains unaltered. The DOF alteration remains at any aperture so you can  use it to deliberately increase DOF. I find it far more effective on static subjects to use focus stacking 

[Dr. G]

6 hours ago, jaapv said:

Yes, that is correct The lens speed remains unaltered. The DOF alteration remains at any aperture so you can  use it to deliberately increase DOF. I find it far more effective on static subjects to use focus stacking 

I agree.  I was referring to the times I need to do it handheld.  

[jaapv]

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Adobe Photomerge is pretty good at aligning the stack. I find it quite possible to stack handheld shots with minimal correction of artefacts, as long as the subject is static.

[JTLeica]

19 hours ago, jaapv said:

Adobe Photomerge is pretty good at aligning the stack. I find it quite possible to stack handheld shots with minimal correction of artefacts, as long as the subject is static.

I agree Jaap I use handheld bracketing a lot and then stack / create HDR in ACR or PS... however one thing I learned is that shooting the electronic shutter can cause some wobble, making it harder to align.

[ksrhee]

It seems like there is a lot of confusion around DOF versus perspective.  The crop view does change the DOF given that it changes the COC due to the enlargement.  However, it's still taken by 28mm lens and the perspective remains the same.  

[cookedart]

If it helps at all, I did do a test today to compare the Q3 50mm crop mode vs my OM Systems OM5 with a Panasonic/Leica 25mm f/1.4 shot at f/1.6.

The out of focus area was identical in both shots to my eye, with the Q3 being sharper overall despite being wide open at f/1.7. the resolution was also very similar. Noise levels were also pretty similar. So to me, I think of the 50mm crop mode as a Micro Four Thirds equivalent.

[JTLeica]

11 hours ago, cookedart said:

If it helps at all, I did do a test today to compare the Q3 50mm crop mode vs my OM Systems OM5 with a Panasonic/Leica 25mm f/1.4 shot at f/1.6.

The out of focus area was identical in both shots to my eye, with the Q3 being sharper overall despite being wide open at f/1.7. the resolution was also very similar. Noise levels were also pretty similar. So to me, I think of the 50mm crop mode as a Micro Four Thirds equivalent.

When you put it like that, that is pretty crazy really. M43 50mm lens included 😬

[cookedart]

6 hours ago, JTLeica said:

When you put it like that, that is pretty crazy really. M43 50mm lens included 😬

Yes, no doubt. It really extends the usefulness of the Q3. I usually bring a spare body with me on most days, and having the Q3 be able to handle everything from 28-50mm very well is fantastic for me. The second body will be relegated to ultrawide specifically.

[Qwertynm]

vor 8 Stunden schrieb JTLeica:

When you put it like that, that is pretty crazy really

you can also think about it this way: the croplines/framelines represent the used sensor area

[01af]

Am 1.3.2024 um 21:57 schrieb ksrhee:

... it's still taken by 28 mm lens and the perspective remains the same.

Focal length doesn't have 'perspective.'

[ksrhee]

11 minutes ago, 01af said:

Focal length doesn't have 'perspective.'

Yes, you are right.  What I meant to say was that whether it's cropped or not, the picture was taken from the same distance.  Doesn't matter whether you use 28mm or 200mm telephoto lens.  The perspective remains the same as long as you don't move.  

[01af]

vor 23 Minuten schrieb ksrhee:

... the picture was taken from the same distance.

Duh ... was it?

[Dr. G]

On 3/4/2024 at 12:16 PM, 01af said:

Focal length doesn't have 'perspective.'

Taking this statement in a different direction...

When comparing a 20mm to a 28mm or 24mm lens, the 20mm lens will show more stretching of the image at the periphery and more changes to the subject when held at different angles.  But if you were to use the 28 or 24mm framing within the center portion of a 20mm lens and moved the lens off axis, would it render the same as if you used a native 28 or 24mm lens and held it the same way releative to the subject?  I don't have a super wide angle lens available, but I'm curious.

[FlashGordonPhotography]

On 3/6/2024 at 7:57 AM, Dr. G said:

Taking this statement in a different direction...

When comparing a 20mm to a 28mm or 24mm lens, the 20mm lens will show more stretching of the image at the periphery and more changes to the subject when held at different angles.  But if you were to use the 28 or 24mm framing within the center portion of a 20mm lens and moved the lens off axis, would it render the same as if you used a native 28 or 24mm lens and held it the same way releative to the subject?  I don't have a super wide angle lens available, but I'm curious.

Assuming all else is the same (lens design, aperture etc), then yes.

Gordon

 

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[PitiWong]

On 11/3/2023 at 11:01 PM, Daniel C.1975 said:

Technically correct, practically not helpful for the question.

 

To the initial question: 

When you crop, you are only using a portion of the sensor, and with the new diagonal of the used sensor area, there is a change of the angle of view. E.g. an 28mm lens on a 35mm sensor does have an angel of view of ~75 degree, with a larger sensor the angle of view would be wider, with a smaller it would be more narrow. So it is the diagonal of the sensor and the focal-length which together defines the angle of view - simply spoken. 

As the Q does use a 35mm sensor, we stick to that equivalent. And yes, even if some people always try to say something different: If you use a crop out of an 28mm photo to simulate 50mm, you have the perspective and image impression of an 50mm lens, used at the same distance with an equivalent aperture. Its physics and mathematics - period. 

To understand what the equivalent aperture at a given crop to a comparable focal length would be, you can use simple math (yes, you can also use more complicated math, but the following is more than sufficient  )

A = aperture (no dimension)

F = focal length mm

d = aperture diameter in mm 

d = F/A = 28mm/1.7 = 16,471mm

 

Now we just solve the equation towards A, while we use F for the via crop simulated focal length (I know technically not the correct terminus, but again, for simplification sufficient):

35mm: A=F/d = 35mm/16,471mm = 2,125 = f2.1

50mm: A= 3,036 = f3

75mm: A=4,554 = f4.6

90mm: A= 5,464 = f5.5

 

Of course you also lose resolution and therefore need to magnify the image more for the same output size, which also leads to a higher magnification of image errors of the lens or the sensor (e.g. chromatic aberrations, noise, ... )

 

 

 

 

 

Hello, 

I just have my Q3 yesterday. This question is always bothering me.

Am I understanding right that when we crop the 28mm photo of Q3, say to 35mm. equivalent,

It does perform as a 35mm. lenses but perform as smaller aperture on a smaller sensor? 

If so, I think I can truly accept and feel free to use the crop mode. 

It is not a simple photo cropping that we can always do it with a simple picture editing tool.

 

[David Wien]

7 minutes ago, PitiWong said:

Hello, 

I just have my Q3 yesterday. This question is always bothering me.

Am I understanding right that when we crop the 28mm photo of Q3, say to 35mm. equivalent,

It does perform as a 35mm. lenses but perform as smaller aperture on a smaller sensor? 

If so, I think I can truly accept and feel free to use the crop mode. 

It is not a simple photo cropping that we can always do it with a simple picture editing tool.

 

I fail to understand your scruples; one is cropping in the camera, the other cropping on the computer. Either achieves the same result. The 35mm issue is simply to expalin that the photo now extends only as far as that of a 35mm lens, not using the full angle of view of the 28mm actual lens.

David