Misconception re: frame lines, DOF, compression

[MindsEye]

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Many of you already know this but depth of field does not change with focal length. The crops for digital zoom in the Q3 (and Q2) will indeed give you the same “compression” and DOF as would those focal length lenses at the same aperture. I have heard/read multiple reviewers incorrectly state that although you have the crop lines you don’t get the same “compression” as actual lenses.

I feel this is important to point out for those that don’t already know it, especially considering the Q3's high resolution sensor, that you have very useable 35mm and 50mm “lenses” built in. You have Q2 resolution at 35mm and M9 resolution at 50mm. Depending on your needs, the 75mm and 90mm may also be very useful.

I’ve seen so many folks wishing for a Q body with a 35mm or 50mm lens. If you are an M user then the frame-line method used on the Q3 will be very familiar and not that different of an experience. I would love to see Leica offer a zoomed-in option in addition to the frame lines on the Q3 (firmware update?) I have that on my Fujifilm X-T5 bodies for digital zoom and love it.

And not insignificantly, you are using the sweet spot of the lens with the digital zoom/crops, so perhaps even better IQ than an actual 35mm or 50mm lens. Maybe not as good an argument at the smallest crops because you are giving up more resolution but really the IQ one “needs” is relative.

I have pointed out elsewhere on this forum that twenty years ago I was selling 40x26 inch prints from an 11MP sensor which was considered "high res" in those days. It took a lot of work being precise with shooting, very little cropping room if any, and using custom interpolation. But I had happy patrons buying those large prints.

Prove it to yourself:

If you want to prove this concept to yourself, lock your camera down on a tripod and use the same aperture and focus point and shoot a couple frames, one with a wide angle and one with a telephoto (zoom lens is easiest). Then import and crop the wide angle to the same framing as the telephoto shot and voila, you will see they look the same. The only difference will be the number of pixels.

Edited June 8, 2023 by MindsEye

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[mikeLD]

Yes, spot on.  I thought I might add that the Q2 has a preview mode which allows you to "post view" the cropped shot you have just taken as long as you don't release the shutter button.  For a street photographer like me that means I can see what I got in the cropped view, then release the shutter button, reframe, and take another without losing the "Decisive Moment".

The Q3 manual indicates the same functionality and I think suggests an additional similar type mode as well...

I can't wait to get my Q3, and then find a good home for my wonderful Q2.  Mine Q3 is on order and pre-paid.  

[Qwertynm]

Please not another discussion about equivalence 😩😂

I don’t think anyone is asking for a Q with a 50 f/3.0 but a Q with a 50 f/1.4 or similar. This you certainly can’t reproduce with the Q3

[MindsEye]

31 minutes ago, mikeLD said:

Yes, spot on.  I thought I might add that the Q2 has a preview mode which allows you to "post view" the cropped shot you have just taken as long as you don't release the shutter button. 

I can't wait to get my Q3, and then find a good home for my wonderful Q2.  Mine Q3 is on order and pre-paid.  

Didn't know about the post view feature. Thanks.

Congrats on your pre-order. I've used one but don't own it yet as I am also waiting on a pre-order.

[MindsEye]

46 minutes ago, Qwertynm said:

Please not another discussion about equivalence 😩😂

I don’t think anyone is asking for a Q with a 50 f/3.0 but a Q with a 50 f/1.4 or similar. This you certainly can’t reproduce with the Q3

Sorry about the repetition for you. It is meant for those that don't realize this. Considering that reviewers for major publications didn't know it, I'm pretty sure several folks on the forum don't realize it either. In addition to my full time photography business I also teach workshops and I have had many advanced and even some professionals that don't know this either.

And yes I get that many users wouldn't be satisfied with an f/3.0 50mm but at 35mm it's about f/2 (Ok, f/2.125) but that's pretty much a summicron at 39MP so for someone like me that might have held off for a 35mm I feel like I will have a very useable 35mm lens, even at f/2.0 which is what I've owned on M cameras in the past. And I can deal with f/3.0 when necessary to have a 50mm lens. 

Naturally everyone has different tastes and use scenarios. Photography is my profession so I have other systems but feel that a Q3 is a wonderful walkabout camera and will augment both my enjoyment and business. I've tried many others for this purpose (Sony RX100, 35mm on M, and 27mm or 23mm on Fujifilm, etc.) but none fit my purpose like the Q3. It it primarily because of the resolution/focal length relationship of the Q3 over previous Q bodies that I am sold. But the rest of the package/features/feel/quality round it out.

Cheers and happy shooting! 😃

Edited June 8, 2023 by MindsEye

[Qwertynm]

My comment wasn’t supposed to be taken seriously. Why would I participate in a technical discussion if I‘m not interested. You‘re right the Q3 is a fine tool and really versatile with its 60MP sensor.

Here are two shots at 50mm

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apart from the Q3 being slightly wider I can‘t see much difference beyond different lens rendering. The Canon is slightly blurry and hazy due to me not being still enough and a Black Pro Mist filter. Tried to match perspective and WB to give a good comparison. If you are shooting groups in low light the Q3 will be the better choice because of a larger DoF when cropped in. Good to have both tools in your toolbox to work with 👍

 

 

[Trankster]

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Interesting.  As a hobbiest dating back to the mid-70s with film cameras shooting wide, normal and telephoto lenses, I believed you choose the "right" lens for the subject matter.  If I am understanding this correctly (from a non-technical point of view), there is no difference assuming the perspective is such to eliminate wide angle distortion.  For example, 28mm photo of a person taken at say 15 feet distance cropped to show their head and shoulders would look identical to a head and shoulders photo taken with a 90 mm lens except for possibly a difference in bokeh.  Is that right? 

Edited June 8, 2023 by Trankster

[MindsEye]

44 minutes ago, Trankster said:

For example, 28mm photo of a person taken at say 15 feet distance cropped to show their head and shoulders would look identical to a head and shoulders photo taken with a 90 mm lens except for possibly a difference in bokeh.  Is that right? 

Yes, in essence that is the case Try the exercise I mentioned above to see for yourself. If you’ve never done it, it’s kinda fun and interesting. 
Here is a pretty good explanation

Happy shooting!

[dpitt]

If you start cropping an image taken by a 28mm lens at F1.7, you will keep the same DOF distance no matter how much you crop at the same distance. So if you shoot a subject and you have 20cm DOF, you will keep that no matter how the crop is.

But because you are only using part of the available light (you crop the rest away) it is as if you are closing the aperture as you crop further and further. So your 'virtual' lens gets slower and slower:

28 at F1.7
cropped to 35mm gives F2.0
cropped to 50mm gives F2.8
cropped to 70mm gives F4.0

So with the Q you can simulate an M with a 50mm Elmarit, but 50 Summicron and 50 Summilux or Noctilux will have much shallower DOF at the same distance when you use them wide open.

[MindsEye]

2 hours ago, dpitt said:

If you start cropping an image taken by a 28mm lens at F1.7, you will keep the same DOF distance no matter how much you crop at the same distance. So if you shoot a subject and you have 20cm DOF, you will keep that no matter how the crop is.

But because you are only using part of the available light (you crop the rest away) it is as if you are closing the aperture as you crop further and further. So your 'virtual' lens gets slower and slower:

28 at F1.7
cropped to 35mm gives F2.0
cropped to 50mm gives F2.8
cropped to 70mm gives F4.0

So with the Q you can simulate an M with a 50mm Elmarit, but 50 Summicron and 50 Summilux or Noctilux will have much shallower DOF at the same distance when you use them wide open.

Thanks for this and your chart. Qwertynm and I discussed this above but your chart is clearer for comparing DOF equivalents. However, the equivalent aperture, in simple terms, only applies to depth of field, not exposure. Your exposure isn't going to change by cropping in. I'm guessing this is part of your point...so your use of the term "slower" wouldn't apply to exposure. Of course the amount of information/number of pixels are reduced as you crop.

This can be an involved topic. But I think the bottom line, in terms of the Q3 or Q2, is that you increase the depth of field for a given aperture as the sensor "size" effectively decreases by using the frame-line crops.

If you want a heady explanation with a lot of other technical aspects thrown in, check out Mirrorlessons blog post on this.

Edited June 9, 2023 by MindsEye

[Lelmer]

1 hour ago, MindsEye said:

......

If you want a heady explanation with a lot of other technical aspects...

No no, I just want a Q with a 35/40mm FL 😊

Having said that, what you explained makes perfect sense, and I appreciate your enthusiasm for the Q3 😉

[Ozymandias]

5 hours ago, dpitt said:

If you start cropping an image taken by a 28mm lens at F1.7, you will keep the same DOF distance no matter how much you crop at the same distance. So if you shoot a subject and you have 20cm DOF, you will keep that no matter how the crop is.

But because you are only using part of the available light (you crop the rest away) it is as if you are closing the aperture as you crop further and further. So your 'virtual' lens gets slower and slower:

28 at F1.7
cropped to 35mm gives F2.0
cropped to 50mm gives F2.8
cropped to 70mm gives F4.0

So with the Q you can simulate an M with a 50mm Elmarit, but 50 Summicron and 50 Summilux or Noctilux will have much shallower DOF at the same distance when you use them wide open.

Thanks dpitt for these details. To take this a bit further, do you use a multiplying factor or similar to give the changed f ratio?  I would like to know - for the Q3 - what the f equivalents are for the inbuilt cropping factors of 75mm and 90mm with the 28mm f1.7 lens. You have already supplied the 35mm and 50mm, thanks.

Paul

[tom0511]

if this was not working the crop modes of Q3 wouldn't make any sense.

 

[Qwertynm]

vor 1 Stunde schrieb Ozymandias:

do you use a multiplying factor or similar to give the changed f ratio?

yes: 75/28 * f/1.7 = f/4.5 (the lens on the Q is more like a 26mm so it would be more like f/5.0)

but as @MindsEye already said it's only in terms of depth of field. You retain the aperture of f/1.7 but gain  more DoF due to the sensor area becoming smaller by cropping the image or cutting away the edges of the image. In some circumstances this can be beneficial. For example if you try to shoot images in available light of a group of people where you'd normally stop down a bit to get everyone in focus.

[Mikep996]

To me all the calculations, etc are unnecessary.  🙄  Just look at the photos.  Do you like the photos from the various crops/do they meet your needs or not?   

[Anakronox]

43 minutes ago, Mikep996 said:

To me all the calculations, etc are unnecessary.  🙄  Just look at the photos.  Do you like the photos from the various crops/do they meet your needs or not?   

Well, the calculations are helpful to know from a technical perspective. 

However, I’ve never seen a photo and thought “ugh, this sucks because it’s not minimum 95% bokeh.”  Noctilux shooters, come at me.  That’s 95% sarcasm by the way 😜

 

[Qwertynm]

The calculations might be trivial for photography but relevant to understand the concept. 

[dpitt]

3 hours ago, Ozymandias said:

Thanks dpitt for these details. To take this a bit further, do you use a multiplying factor or similar to give the changed f ratio?  I would like to know - for the Q3 - what the f equivalents are for the inbuilt cropping factors of 75mm and 90mm with the 28mm f1.7 lens. You have already supplied the 35mm and 50mm, thanks.

Paul

Yes it is a simple formula. If you crop by 1,41 then the DOF effect is equivalent to the square of that (i.e. 2x) so cropping from 35 F2.0, by 1,41  results in:

FL : 35 x 1,41 = 49,35 ~ 50
Aperture DOF effect : F 2.0  by half (1,41 x 1,41 = 2) so it becomes F2.8 =  1 stop less than the 35mm has

Mind you, that the exposure needed to take the picture is not influenced, so when you crop it is only the apparent FL and DOF that changes, not the shutter time.

 

Edited June 9, 2023 by dpitt

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[dpitt]

1 hour ago, Qwertynm said:

yes: 75/28 * f/1.7 = f/4.5 (the lens on the Q is more like a 26mm so it would be more like f/5.0)

but as @MindsEye already said it's only in terms of depth of field. You retain the aperture of f/1.7 but gain  more DoF due to the sensor area becoming smaller by cropping the image or cutting away the edges of the image. In some circumstances this can be beneficial. For example if you try to shoot images in available light of a group of people where you'd normally stop down a bit to get everyone in focus.

You are right, I rounded off to f 4 because I used 70 and not 75mm. If you take 75 and 26 it is indeed more like F5.0 and very close to F5.6

[Simone_DF]

1 hour ago, Mikep996 said:

To me all the calculations, etc are unnecessary.  🙄  Just look at the photos.  Do you like the photos from the various crops/do they meet your needs or not?   

No.

Now please give me a Q with a 50mm f/2 or faster.