Digital cropping vs prime lens - Pros & Cons

[Petrichor]

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I have read on these forums that a prime lens will always produce a ‘better’ image that a digital crop (understanding that the raw file remains unchanged irrespective of digital crop) Some claim the difference is immediately obvious. I cant see an obvious difference on the iPad when I look at a digital crop JPEG and wouldn't know what to look for.

I have looked on these forums for an understanding of the difference beyond the mere assertion of fact.

Can someone please explain and perhaps display the difference between digital zoom and the corresponding actual focal length e.g. Q2 native 28 cropped 35 (vs 35 prime) or 50 (vs 50 primes); M11 native 50mm cropped 1.3 (say 70mm prime) or 1.8 (90 prime) 

** Of course if this has been explained I’d be grateful to be redirected.

Thank you

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[Ko.Fe.]

"better".... 

I would call it as more natural. Amount of MP has nothing to do with lens optical character.

And, honestly, what is the point of getting M camera and have it cropped? Frame it on the spot.  

The beauty of M is in framelines allowing you to see outside of framelines and make easier decision on framing. 

 

But I like how they have it implemented framelines via crop in Q. 

 

As for viewing on iPad... I'm terribly sorry, but for such technicalities you will be better served on monitor, graphics card supporting more suitable size. 

 

[frame-it]

 

[SrMi]

3 hours ago, Petrichor said:

I have read on these forums that a prime lens will always produce a ‘better’ image that a digital crop (understanding that the raw file remains unchanged irrespective of digital crop) Some claim the difference is immediately obvious. I cant see an obvious difference on the iPad when I look at a digital crop JPEG and wouldn't know what to look for.

I have looked on these forums for an understanding of the difference beyond the mere assertion of fact.

Can someone please explain and perhaps display the difference between digital zoom and the corresponding actual focal length e.g. Q2 native 28 cropped 35 (vs 35 prime) or 50 (vs 50 primes); M11 native 50mm cropped 1.3 (say 70mm prime) or 1.8 (90 prime) 

** Of course if this has been explained I’d be grateful to be redirected.

Thank you

You need to compare them at the same size, i.e., reduce the full-size JPEG to the cropped JPEG size.

[evikne]

The lens designers put a lot of work into making the lens so that it performs well over the entire image surface. When we crop an image, we only use a part of it, and then scale up.

For a similar reason, Karbe encourages us to photograph as much as possible with an open aperture; because by stopping down, we only use a small part of the lens's potential, and cut away what the designers have worked on the most.

[Jeff S]

Cropping from a fixed camera position (or in PP) will maintain perspective, while moving one’s feet when using prime lenses will offer changing perspective.

For rendering comparisons between full/cropped images from same camera position, I suggest making prints, not screen shots.

Jeff

[Jean-Michel]

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Whether you 'crop' in-camera or in processing the image later, the amount of informations is reduced. For instance, using your Q2 example, the full size image is has 47 Mpx, cropping to a 35 mm view makes that image using 30 Mpx, 15 Mpx for the 50 mm view, and 6.5 Mpx for the 75 mm view. If you only make small prints, such as 4 by 6 inches, then a 6.5 Mpx file is quite fine, but if you print larger sizes then you may be restricted in the maximum size printed. And if you do not print, then the whole exercise is largely irrelevant. 

[250swb]

On 5/7/2023 at 11:21 PM, Petrichor said:

I have looked on these forums for an understanding of the difference beyond the mere assertion of fact.

If for the sake of argument you crop an image by 50% you still have the same number of pixels per inch as zooming in to the 100% image, which is what I suspect you are doing, and you won't see a difference. But the 50% image is only half the size of the 100% image. So now you want to now make a print, or post a good image in the Leica forum, and the 50% image is too small at maybe 4x5 and it needs to be 8x10 (the original size of the uncropped image for the sake of argument), but increasing the size doesn't increase the number of pixels in your cropped image, so effectively you've gone from using a 24mp camera (or whatever) to a 12mp camera by using a 50% crop and thus reduce the resolution of the file/print.

Clearly things get somewhat better visually with a cropped image the higher number of pixels you start with (which is why the Q gets away with it), but cropping reduces the number of pixels you are using if you retain the original image size, so the visual quality of the file goes down. If however you go from a 50mm lens to a 100mm lens and 'crop the scene' you are still using the full size of the sensor for both lenses, and all things being equal the files from both will be at the maximum resolution.

Edited May 9, 2023 by 250swb

[ianforber]

I know many people consider any significant crop as somethings to be avoided but I take a different view (no pun intended!). I invested in my high megapixel Leica cameras precisely so that I could crop, sometimes to ridiculous extents. I do so because it gives me something that is good enough an approximation of what a longer focal length lens would provide so that I don’t have to carry lots of lenses around with me. It’s not the same though.

As I understand it, if I crop a picture taken on my Q2 (ie 28mm) at f2.8 give the same view as if I had taken it on a 90mm f2.8 and then, without moving so that I am not changing the distance between me and the subject, take the same picture with a 90mm f2.8, the latter will have more compression and greater background blur. For a landscape photographer, the compression is important because it makes distant objects such as hills, mountains etc look closer together and gives a very different look. For portraits, subject separation by use of background blur is important, as is the fact that you can stand back from your subject and get a head and shoulders shot without standing so close that it risks over emphasising facial features such as the nose or jawline

For me though, cropping is good enough. @jaapv is far better informed than I am and may be along shortly to correct me!

[jaapv]

1 hour ago, ianforber said:

latter will have more compression[

 No it won't The perspective will be identical to a 90 mm lens  OOF sharpness will be affected. .  Examples are 28-70 mm.

28 mm no crop

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70 mm 

 

 

28. mm cropped to 70 mm

 

[ianforber]

I knew I’d get something wrong! Thanks @jaapv  

[Jeff S]

1 hour ago, ianforber said:

I knew I’d get something wrong! Thanks @jaapv  

Post # 6. Moving your feet changes perspective.

Jeff

Edited May 23, 2023 by Jeff S

[ianforber]

4 hours ago, Jeff S said:

Post # 6. Moving your feet changes perspective.

Jeff

I think I was both wrong and expressed myself poorly. Sorry if I misled the OP

[kathala]

cropping to the extent you describe (28 to 35 or 5o to 75) is irrelevant in terms of disadvantages.

buying a fixed lens camera with the intent of mostly using it in crop mode, as a post suggests, is however silly, I'd contend. then again, buying a fixed lens digital cameras is silly outright, I'd say, since the camera becomes obsolete much faster than the lens, but that's a different story.

I've lived by the old adage to have lenses of roughly double focal lengths and crop the intermediaries if needed. So I carry a 10, 18, 28, 5o, 9o and 2oo. were I to need a 35 angle of view, I'd crop the 28.

but for the tiny resolution that digital presentation (ipad, insta, ...) requires, you could even crop that 28 to 5o or 9o. I had 1 MPix crops out of 8 MPix files printed when nothing else was available. however, MAXIMUM print size goes way down, of course, and grain and aberrations become much more noticeable. and whilst we have established that perspective does not change, depth of field does. 

[UliWer]

Here I tried a comparison of croppings from a 24mm with 50,90 and 135mm: 

I'd say that the cropping method can stand comparison with the original from a lens with 2*focal length (24mm and 50mm). I never use this method in the "normal" range but to avoid carrying long tele-lenses it may be very helpful to crop from an original taken with 90mm to the field of view of an 180mm, or from 135mm to 270mm.  

[IkarusJohn]

I straighten and crop when I need to, but very rarely to simulate a different focal length.

Call me old fashioned, but this idea of a single focal length, and high resolution sensor, with built in cropping leaves me completely cold.  I accept that composition comes first and foremost, and to that end modern advances of digital photography should strengthen composition - I’m not sure it does though.

I have always been fascinated by cameras, and I love what lenses do, from the Petzval un-loved in my cupboard, to the APO 35 Summicron I bought the other day - each needs to be understood and used to its strengths (a life long project).  I can’t get away from thinking of framing in the focal length I’m carrying, and thinking how to frame to make the most of the lens.  I’m not very good at it, but I keep trying - tight framing and foreshortening with a telephoto, or getting close with a wide angle - each has the opportunity to introduce drama.  I hate to think of not using the entire field of view and all that a particular lens gives.

I’ve never particularly warmed to zooms, when a fixed focal length is available.  The latter makes me think …

[M11 for me]

I tend indeed to take less lenses with me since I own the M11. My favourite lens is the 28mm. Before I bought the the M11 I always carried a small waist pack with some additional 2 or 3 lenses. Of course most time I still take more than one lens with me but it's no disaster (in my head) anymore if I have the 28mm lens only. I know that I can crop.

I just recently came back from a trip to Donegal and I had another Q with me instead of the M11. My wife had her Q2 as well, so we had both 28mm. And as a result for nature or landscape the 28mm fitted so perfectly well. And in post I had only few cases that I wanted to crop as 28mm normally fitted perfectly well. That was my first finding. And if I had to crop some pictures in post I did not hesitate to do so. The result is absolutely good enough. That is then my second finding.

My personal conclusion: I go much lighter with only one lens (Q or M11). And with 60MPix I know that I can crop without any punishment. The high MPix sensor helps me to go lighter than ever before.

The fact that I went with  Q only to Ireland was a conscious decision: Go light. I never ever did this before. And it was a big success in my mind.

I am a strong candidate for the Q3 (Hope it comes today 🥰).

Edited May 25, 2023 by M11 for me

[pgk]

On 5/7/2023 at 11:21 PM, Petrichor said:

Some claim the difference is immediately obvious.

It all depends on the degree of enlargement you put the final (cropped or otherwise) image to. If you enlarge vastly then an uncropped file will probably produce a better final image. If you don't then up to a point, cropped or files should be adequate. As ever the question might sound simple but the answer  isn't and depends on a lot of factors. Its not simply a matter of producing equivalent images.

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