Q3 Crop Modes and Equivalent Depths of Field Question

[RBNvRBN photo]

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There IS a difference in DOF between between the cropping mode in the Q3 to e.g. 90mm (resulting in a 6MP image) at 1.7 and putting an 90mm 1,7 lens on a 6MP full frame sensor. In the Q3 only a small center portion of the sensor is used to make that '90mm equivalent' image. It is the same however to any camera that would utilize a smaller sensor of that size (same size as the cropped part) and having a 28mm 1.7 lens on it. The camera manufacturer selling such camera might even refer to or market it as a '90mm equivalent to full frame'. But it is not. That's why we've moved on from APS-C sensors to full frame and some take the next step to medium format... 

Of course it's nice to have the large number of pixels so we can crop quite a bit and still have enough pixels to make large prints, but an 28mm 1.7 image (it seems the actual focal length is closer to 24) stays an 28mm 1.7 image no matter how much, where or when you crop.

The smaller sensor size is why smartphones have a very large DOF and why some use software tricks to 'blur' the background to sort of emulate the DOF effect of a larger sensor (often part of a 'portrait mode').

An interesting point is that the camera will meter only the 'cropped' part of the image. So, beware of blown highlights if you intend to use the full image later.

I don't know if Leica reads these forums. It would be nice to have the option to use the crop guides only as guides resulting in no crop at all (not even in the JPG). I know many people use these guides (set to 35mm) in a 'rangefinder' style to see what is entering the frame. And it would be perfect to also have these guides in different aspect ratios (like square) as well but still be able to see the whole screen. So we have the 'guide/grid' during the shoot, but also have full control in post (not just in the DNG). Maybe it could be some extra variants to the grid option (which now only shows a 'rule of the thirds' grid). It wouldn't be so hard to accomplish because it would be just an overlay on the EVF or screen.

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[Qwertynm]

vor einer Stunde schrieb RBNvRBN photo:

There IS a difference in DOF between between the cropping mode in the Q3 to e.g. 90mm (resulting in a 6MP image) at 1.7 and putting an 90mm 1,7 lens on a 6MP full frame sensor.

yes, I think no one disputes that?

regarding the frame lines: why not shoot dng? jpg conversions on a smartphone are a thing and with the Leica Fotos app and LR mobile a breeze.

[jaapv]

Yes but equivalent aperture is an ambiguous term. It suggests that exposure will change as well, which obviously is not the case.
Quite a few less informed photographers coming to this forum would be confused as this is one of the subjects where Internet information is all over the landscape. Better to use the word DOF in the first place  

 

4 hours ago, Corius said:

I wrote "Equivalent Aperture". ie the Aperture that would required when capturing with a full frame sensor that yields the same DOF as that produced by a cropped image

So, a Q3 50mm crop at f3.2 has the same DOF as a full frame image captured with a 50mm lens at f5.7.

 

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2 hours ago, Qwertynm said:

yes, I think no one disputes that?

No, but it was the original question from the OP and the resulting discussion was not entirely clear (to me at least). Maybe, they were thinking about either getting an SL or M with longer focal length lenses or getting the small Q3 and just do the cropping and expecting that the outcome will be the same. The answer is it won't.  

2 hours ago, Qwertynm said:

regarding the frame lines: why not shoot dng? jpg conversions on a smartphone are a thing and with the Leica Fotos app and LR mobile a breeze.

I do shoot DNG. But having a frame (for instance square format which I love) helps me to compose the image in a way that allows me to crop it the way I want. It could, for instance, mean that I need to take a small step to the left or to the right to give me the lines in the frame where I want them. Having a guide can help you do that. So when you are in post you know that when cropping it the right way, the image you envisaged is there (afterwards you cannot make adjustments to the point where you took the photo - you can only crop). Leica - being the ultimate photographer's brand - could help us achieve those things a bit easier with a few simple gridlines. I even reckon it is relatively easy to add this to the camera (just a few lines in the EVF/display.  

[Qwertynm]

vor einer Stunde schrieb RBNvRBN photo:

I do shoot DNG. But having a frame (for instance square format which I love) helps me to compose the image in a way that allows me to crop it the way I want

there are other in camera crop formats, for example 1:1, 16:9 and 4:3 if memory serves me right. If you shoot dng anyway, those are reversible in post and show on the display/EVF if applied. So I guess I don't fully understand what exactly you want  your Q3 to do. As it seems, you could set it up like you said you'd find helpful? Or what am I missing? Anyway, I'd suggest instead of requesting features on a forum online only a handful of people read, get the Leica Fotos App for your smartphone, navigate to Settings > Feature Request and send an email directly to Leica. The more feedback they get, the better (imho). The Q3 has lots of room for improvement. It's already a great camera that could be even better.

[RBNvRBN photo]

3 hours ago, Qwertynm said:

there are other in camera crop formats, for example 1:1, 16:9 and 4:3 if memory serves me right.

There indeed is, but it cuts the vision in the viewfinder to that format. I would like to have that as a grid in the viewfinder so you can still see what's happening outside the frame (much like a rangefinder). I know many people use the 35mm setting only as a guide to give them some leeway framing. Thanks for the tip of the app. I'll check it out and do the request there.

[ksrhee]

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29 minutes ago, RBNvRBN photo said:

There indeed is, but it cuts the vision in the viewfinder to that format. I would like to have that as a grid in the viewfinder so you can still see what's happening outside the frame (much like a rangefinder). I know many people use the 35mm setting only as a guide to give them some leeway framing. Thanks for the tip of the app. I'll check it out and do the request there.

Not sure what you are asking. The Q3 does gives you the frame line when you select different cropping modes. 

[SrMi]

45 minutes ago, ksrhee said:

Not sure what you are asking. The Q3 does gives you the frame line when you select different cropping modes. 

Changes to the Photo Aspect Ratio are different from Digital Zoom (crop). Changing the aspect ratio does not give frame lines, but it blacks out anything outside the selected aspect ratio.

[ksrhee]

3 hours ago, SrMi said:

Changes to the Photo Aspect Ratio are different from Digital Zoom (crop). Changing the aspect ratio does not give frame lines, but it blacks out anything outside the selected aspect ratio.

I thought he was talking about the cropping mode, not aspect ratio.  The Leica behavior is typical of other cameras with EVF as well.  

[getoutofgotham]

On 11/4/2023 at 11:57 AM, SrMi said:

To stress again, 'optical' DOF is neither a scientific nor a practical term.

It doesn't matter if it's a term you accept, it's a specific objective context that has a clear, factual answer. It's an interesting distinction, whether it's one that the photography community has ever regularly considered, or has assigned any meaning to, let alone terms. It's useful to newcomers to know that no, cropping into an image, after it's been recorded, naturally, does not change the pixel value of those remained pixels in the image. You may not find it useful, but that's fairly pedagogical thinking, and doesn't negate the value others see in the question and distinction. But this is fairly typical of the photographers and scientist community, rarely allowing themselves to step back and see things from creative thinkers perspective. It's an overly pedantic field IMO and this thread proves it.

[getoutofgotham]

On 1/11/2024 at 6:55 AM, thegobi said:

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 😉

 

But there is absolutely no difference in DOF between sensor/film plane sizes, when accounting for equivalent aperture and exact same camera position and scene. The only difference is the practicality and availability of glass that achieves faster apertures as you shrink down from FF, that's it, which leads to the misconception that smaller sensors have deeper DOF. They simply do not.

[Qwertynm]

vor 2 Stunden schrieb getoutofgotham:

The only difference is the practicality and availability of glass that achieves faster apertures as you shrink down from FF, that's it, which leads to the misconception that smaller sensors have deeper DOF. They simply do not.

you lament the "overly pedantic field" of photographers and scientists but you're beating on the same drum here. @jaapv just close that thread already, please 🫣

[getoutofgotham]

16 minutes ago, Qwertynm said:

you lament the "overly pedantic field" of photographers and scientists but you're beating on the same drum here. @jaapv just close that thread already, please 🫣

Imagine believing that refuting misinformation in a single sentence is pedantry. 

[01af]

vor 5 Stunden schrieb getoutofgotham:

It doesn't matter if 'optical depth-of-field' is a term you accept, it's a specific objective context that has a clear, factual answer.

No, it isn't, and it hasn't. It's just bunkum.

.

vor 5 Stunden schrieb getoutofgotham:

It's useful to newcomers to know that no, cropping into an image, after it's been recorded, naturally, does not change the pixel value of those remained pixels in the image.

This is not particularly 'useful.' It's just a trivial and undisputed fact, even among newcomers.

.

vor 5 Stunden schrieb getoutofgotham:

... and doesn't negate the value others see in the question and distinction.

The only 'value' of the term optical depth-of-field is to evoke misconceptions about depth-of-field. But in fact, depth-of-field is neither a property of the lens nor a property of the pixels. It's a property of the image.

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vor 4 Stunden schrieb getoutofgotham:

... which leads to the misconception that smaller sensors have deeper depth-of-field. They simply do not.

Here you're right, for a change. Because as a matter of fact, smaller sensors have shallower depth-of-field.

In order to get deeper depth-of-field out of a smaller-sensor camera you'd have to change two parameters: sensor size and focal length. In fact, this is the usual thing to do because we want to compare equal images, so we need equal fields-of-view, hence equivalent (as opposed to equal) focal lengths. And if you do that then the smaller-sensor camera, for the same aperture and distance, will yield deeper depth-of-field. But the causative factor is the shorter focal length, not the smaller sensor. Depth-of-field is proportional to linear sensor size and inversely proportional to the square of the focal length.

Cropping, however, doesn't change focal length and does lead to a different image, effectively using a smaller portion of the sensor. So compared to the uncropped image, it has shallower depth-of-field. Compared to the same (notional) image taken with a longer focal length on the uncropped sensor, it has deeper depth-of-field.

Edited May 14, 2024 by 01af

[jaapv]

All correect with this addendum:  assuming that the magnification of the image is proportional to the crop value.  If you keep the magnification the same, i.e. the final cropped image is smaller than the original and viewed at the same distance, the DOF will be the same. 

[01af]

vor 12 Minuten schrieb jaapv:

If you keep the magnification the same, i. e. the final cropped image is smaller than the original and viewed at the same distance, the DOF will be the same.

That's correct—but highly misleading.

In order to properly compare depths-of-field of different images, we need to look at the same print sizes from the same viewing distance. Otherwise we'd just fool ourselves.

[jaapv]

 

1 hour ago, 01af said:

That's correct—but highly misleading.

In order to properly compare depths-of-field of different images, we need to look at the same print sizes from the same viewing distance. Otherwise we'd just fool ourselves.

That is exactly the point that I am making. The whole confusion arises from people thinking that DOF is a property of cameras and lenses that can be caught in formulas and numbers That is only true to a certain extent.
First define DOF. It is a phenomena that is caused by the resolution limit of human vision - which is individually variable.
Then it depends on the subject: A low-contrast, low detail subject without  sharp transitions will show deep DOF; a high-detail, high contrast subject with sharp transitions will show narrow DOF.
Then it goes through the imaging chain, subject distance - lens and sensor properties - enlarger or computer, and ends up as an image of a certain size and when viewed at a given distance  will be seen though human vision which will determine what detail can be resolved. Anything that cannot be resolved will be perceived as equally sharp.

So in the end we have a purely biological effect that is controlled by the properties of the subject and magnification. The camera is only  a tool that produces the magnification  

This leads to utter confusion and misunderstanding when catching the function of the camera tool in formulas.
Just replace the camera by binoculars. Narrow FOV=crop, magnification, narrow DOF.  The specification of binoculars is not even given in focal length but in magnification. 
Or look at the same scene at night or in sunlight.Pupils close-more DOF. 

[jaapv]

On 5/13/2024 at 10:22 AM, Qwertynm said:

yes, I think no one disputes that?

regarding the frame lines: why not shoot dng? jpg conversions on a smartphone are a thing and with the Leica Fotos app and LR mobile a breeze.

It is easier to crop for composition on a screen than in the viewfinder too. Or just do it the way painters do- use your fingers to visualize a frame before putting a brush to the canvas or the camera to your eye. 

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Hallo,

Look here: Leica Q

[ksrhee]

2 hours ago, 01af said:

That's correct—but highly misleading.

In order to properly compare depths-of-field of different images, we need to look at the same print sizes from the same viewing distance. Otherwise we'd just fool ourselves.

This is absolutely correct.  BTW, the sensor size itself doesn’t impact the depth of field.  For those of you who are new, here is a useful link to the topic:  https://www.diyphotography.net/how-sensor-size-affects-depth-of-field/#:~:text=The smaller the sensor%2C the greater the depth of field.&text=Longer focal-length lenses create,length than the sensor size.

[01af]

vor einer Stunde schrieb ksrhee:

The sensor size itself doesn’t impact the depth of field.  For those of you who are new, here is a useful link to the topic: [...]

Hmm. Obviously you didn't fully understand the web page you're referring to. Otherwise you wouldn't deny that sensor size does impact depth-of-field. While this page is basically correct most of the time technically, it is very confusing paedagogically due to sloppy language and flimsy explanations. I strongly deplore the notion of 'three viewpoints.' After all, it addresses three different things, not just three viewpoints on the same thing. And in the first so-called ... umm, 'viewpoint,' the text even contradicts itself.