medium format compression

Started Apr 9, 2017 | Discussions
xoda Regular Member • Posts: 284
medium format compression

if we're shooting 24mm on a medium camera, and let's suppose it's a 16mm equivalent on full frame.

i know the 24mm would give lower depth of field simply because it's a longer lens. But if it's equivalent to a 16mm FF, that should mean it needs to be placed the same distance from the subject as the 16mm on the full frame if they are to get the same composition right?

In that case, does the 24mm give any additional compression vs the 16mm? Although longer focal length is often used to compress the foreground and background, my understanding was that ultimately it's the distance between the camera and subject that determined compression

JimKasson
JimKasson Forum Pro • Posts: 25,752
Re: medium format compression
2

xoda wrote:

if we're shooting 24mm on a medium camera, and let's suppose it's a 16mm equivalent on full frame.

i know the 24mm would give lower depth of field simply because it's a longer lens. But if it's equivalent to a 16mm FF, that should mean it needs to be placed the same distance from the subject as the 16mm on the full frame if they are to get the same composition right?

Right.

In that case, does the 24mm give any additional compression vs the 16mm?

No.

Although longer focal length is often used to compress the foreground and background, my understanding was that ultimately it's the distance between the camera and subject that determined compression

Perspective is perspective, and is unchanged by the lens.

Jim

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Macro guy
Macro guy Veteran Member • Posts: 4,094
Re: medium format compression
1

xoda wrote:

if we're shooting 24mm on a medium camera, and let's suppose it's a 16mm equivalent on full frame.

i know the 24mm would give lower depth of field simply because it's a longer lens. But if it's equivalent to a 16mm FF, that should mean it needs to be placed the same distance from the subject as the 16mm on the full frame if they are to get the same composition right?

In that case, does the 24mm give any additional compression vs the 16mm? Although longer focal length is often used to compress the foreground and background, my understanding was that ultimately it's the distance between the camera and subject that determined compression

Compression, which is part of perspective is a function of lens to subject distance, not focal length.  So, as long as both cameras are at the same spot in relation to the subject, the perspective will be the same.

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left eye
left eye Senior Member • Posts: 1,771
Re: medium format compression
1

xoda wrote:

if we're shooting 24mm on a medium camera, and let's suppose it's a 16mm equivalent on full frame.

i know the 24mm would give lower depth of field simply because it's a longer lens. But if it's equivalent to a 16mm FF, that should mean it needs to be placed the same distance from the subject as the 16mm on the full frame if they are to get the same composition right?

In that case, does the 24mm give any additional compression vs the 16mm? Although longer focal length is often used to compress the foreground and background, my understanding was that ultimately it's the distance between the camera and subject that determined compression

I find that although the longer focal length on the larger format provides the same angle of view, etc, distortion is better controlled, the results look more 'solid'.

In other words, when you use a wide angle [or super wide] on MF the visual 'warping' effect at the corners is not so extreme as with an equivalent shorter focal length on a smaller format.  This makes MF ideal for architectural photography, or in fact any photography requiring wide-angle!

There's probably some optical science behind this fact; the above is just in my experience.

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Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 2,959
Re: medium format compression

Hi,

Perspective is same. It may be possible that geometric distortion is lower on some MFD lenses. Many modern lenses are corrected in software, however. That applies definitively to Hasselblad lenses.

But, there is no way format can anything related to perspective.

Best regards

Erik

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Paul Regular Member • Posts: 293
Re: medium format compression
1

i am not sure i have the correct understanding of the word compression here. In my experience and coming from shooting a lot of 4x5 and almost exclusively medium format film this is the one and only major issue i have with digital capture. A 90mm lens will always be a 90mm lens but on a 4x5 camera it will have to cover a much bigger "sensor", so the angle of view on that camera will be like a wide angle lens. I don't want to say it will look like a X mm lens on X format because it won't.

The best way to describe it is to think of a 4x5 camera sitting next to a (lets say) 5D (35mm FF) and both have a 90mm lens (made for each camera) at about 6ft from a person sitting on a chair. the 5D image will probably produce a tight-ish head shot portrait, the 4x5 will probably show most of the person with room around it.

If you would switch lenses on the 5D to show the same angle of view, the image would look very different because the depth perception (compression?) of that wider angle lens for 35mm would distort the image much more then the 4x5 image.

the larger the "sensor" area, the easier it is to get a wider view (angle) image without a wide angle (distorted, extreme depth) look. this is most important with portraits IMO.

the fuji gx 680 and 6x9 used to be my favorite cameras for the simple reason that you could stand a couple of feet from a person, get almost their whole body in the shot but never have their features distorted the way the same shot (of angle of view) would have looked with a 24 or 28mm on a FF 35mm camera.

JimKasson
JimKasson Forum Pro • Posts: 25,752
Pinholes

Paul wrote:

i am not sure i have the correct understanding of the word compression here. In my experience and coming from shooting a lot of 4x5 and almost exclusively medium format film this is the one and only major issue i have with digital capture. A 90mm lens will always be a 90mm lens but on a 4x5 camera it will have to cover a much bigger "sensor", so the angle of view on that camera will be like a wide angle lens. I don't want to say it will look like a X mm lens on X format because it won't.

The best way to describe it is to think of a 4x5 camera sitting next to a (lets say) 5D (35mm FF) and both have a 90mm lens (made for each camera) at about 6ft from a person sitting on a chair. the 5D image will probably produce a tight-ish head shot portrait, the 4x5 will probably show most of the person with room around it.

If you would switch lenses on the 5D to show the same angle of view, the image would look very different because the depth perception (compression?) of that wider angle lens for 35mm would distort the image much more then the 4x5 image.

the larger the "sensor" area, the easier it is to get a wider view (angle) image without a wide angle (distorted, extreme depth) look. this is most important with portraits IMO.

the fuji gx 680 and 6x9 used to be my favorite cameras for the simple reason that you could stand a couple of feet from a person, get almost their whole body in the shot but never have their features distorted the way the same shot (of angle of view) would have looked with a 24 or 28mm on a FF 35mm camera.

Would you say the same thing if the lenses in question were pinholes? If so, how would the geometry be different except for scaling? If not, why not?

Jim

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Paul Regular Member • Posts: 293
Re: Pinholes

i don't have much experience with pinhole cameras, but since there is no glass involved i would assume that the image captured depends on the distance between the hole and the film plane as well as the size of the capture area. the hole is just there to let enough and or not too much light in.

the whole idea of having a lens  instead of a hole is to tweak the light coming in and hitting the capture area and depending on the design of the lens this will look a certain way.

again: if i am standing with my back to a wall, i might be able to capture the entire opposite wall with (for example) a 24 mm lens on a FF 35mm camera. i will probably also capture the entire wall with a 40mm lens on a 645 camera. but if (for example) there is a window in the middle of that wall and i make 8x10 prints from each camera covering the same area of the wall, the window will look smaller and further away on the FF35mm print.

JimKasson
JimKasson Forum Pro • Posts: 25,752
Re: Pinholes

Paul wrote:

i don't have much experience with pinhole cameras, but since there is no glass involved i would assume that the image captured depends on the distance between the hole and the film plane as well as the size of the capture area.

Just as with a glass lens.

the hole is just there to let enough and or not too much light in.

The hole is there to focus the light.

the whole idea of having a lens instead of a hole is to tweak the light coming in and hitting the capture area and depending on the design of the lens this will look a certain way.

What if we do out thought experiment with glass lenses and say that they must all have the same design, but scaled to the format involved, which with scale focal length and f-stop equivalently?

again: if i am standing with my back to a wall, i might be able to capture the entire opposite wall with (for example) a 24 mm lens on a FF 35mm camera. i will probably also capture the entire wall with a 40mm lens on a 645 camera. but if (for example) there is a window in the middle of that wall and i make 8x10 prints from each camera covering the same area of the wall, the window will look smaller and further away on the FF35mm print.

How can that be? You are postulating distortion that you won't see in a rectilinear lens. Draw lines from the center of the lens to the sides of the image with both formats. The way you set up the problem, the lines will have the same angle between them. So how could say, 1/4 that angle on one camera be different from 1/4 that angle on the other?

Jim

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Paul Regular Member • Posts: 293
Re: Pinholes

i am not sure i can follow. i know what i can see and i did a side by side between A7RII and fuji GFX the other day and i was honestly surprised of how obvious the difference was between the 2 (pretty similar) formats when  capturing a the same angle of view using (obviously) 2 different focal lengths.

using the same focal length on both cameras would obviously create the same depth, but the A7RII file would look cropped, the GFX would show a wider angle. to get the same angle i had to switch to a wider focal length on the A7RII which made the center of same scene appear further away.

i shot tons of files that day and don't keep this stuff. you have tested the gfx in depth and i am very grateful for you testing, i am pretty sure you could easily test this yourself?

i feel like i have tried to say the same thing several times here, to me this is easily visible, the bigger the difference in format, the easier visible.

JimKasson
JimKasson Forum Pro • Posts: 25,752
Re: Pinholes

Paul wrote:

i am not sure i can follow. i know what i can see and i did a side by side between A7RII and fuji GFX the other day and i was honestly surprised of how obvious the difference was between the 2 (pretty similar) formats when capturing a the same angle of view using (obviously) 2 different focal lengths.

using the same focal length on both cameras would obviously create the same depth, but the A7RII file would look cropped, the GFX would show a wider angle. to get the same angle i had to switch to a wider focal length on the A7RII which made the center of same scene appear further away.

i shot tons of files that day and don't keep this stuff. you have tested the gfx in depth and i am very grateful for you testing, i am pretty sure you could easily test this yourself?

i feel like i have tried to say the same thing several times here, to me this is easily visible, the bigger the difference in format, the easier visible.

Maybe I'll do the demo. I have to say when I was shooting 8x10 and 4x5 in the studio, I didn't think twice about taking the same picture with a 300mm lens on the 8x10 and a 150 on the 4x5. The images looked the same to me. I'd sometimes use the 4x5 to get everything right before bringing in the 8x10. Course you'd have to open up the 4x5 two stops to get the DOF the same.

Jim

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Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 2,959
Re: medium format compression

Hi,

Here is a small comparison between MF (49x37mm) using 120 mm at f/8, Sony A7rII using 90 mm at f/5.6 and APS-C using 50 mm at f/4.

The comparison is not perfect. The 120/4 is a macro lens having significant field curvature at long distances, the 90/2.8 may have a tilted focal plane and with the APS-C 60 mm at f/3.8 should have been used, but I had no such lens with me.

Best regards

Erik

https://www.dpreview.com/forums/post/59220761

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Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 2,959
Re: Pinholes

Paul wrote:

i am not sure i can follow. i know what i can see and i did a side by side between A7RII and fuji GFX the other day and i was honestly surprised of how obvious the difference was between the 2 (pretty similar) formats when capturing a the same angle of view using (obviously) 2 different focal lengths.

using the same focal length on both cameras would obviously create the same depth, but the A7RII file would look cropped, the GFX would show a wider angle. to get the same angle i had to switch to a wider focal length on the A7RII which made the center of same scene appear further away.

i shot tons of files that day and don't keep this stuff. you have tested the gfx in depth and i am very grateful for you testing, i am pretty sure you could easily test this yourself?

i feel like i have tried to say the same thing several times here, to me this is easily visible, the bigger the difference in format, the easier visible.

Hi,

Thing like that always depend on not achieving a correct match. If you are shooting with the same focal length from the same position, perspective will not change. But just shifting gear make small changes in position.

Field of view will differ, with the larger sensor giving a wider field of view. You can increase the field of view by switching to a wider lens.

But, your GFX would have a different aspect ratio than your A7rII. Let's assume you are shooting the 63 mm lens. In that case, you would need a 46 mm lens for matching FoV vertically, while you could use a 52 mm lens for a good horisontal match.

If we say 46 mm for vertical match and assume that you were shooting at f/2.8 for minimum DoF, a proper match on the 46 mm would need f/2.0, don't know if you could find a 45 mm that works well at f/2.

Personally, I used to be shooting a P45+ with Hasselblad V lenses. With the 'Blad' I would typically use Zeiss primes at f/11. That aperture is probably a tiny bit in diffraction limited territory, but I felt it was a good compromise with the V-series lenses and also regarding my focusing ability.

With the Sony I would probably shoot at f/8 as a starting point.

I never perceived one was preferable to the other. Often then 4/3 crop ratio of the P45+ back felt optimal, but I often crop blue sky so the wider crop of 36x24 mm often also works.

I would say that it is better to just enjoy shooting with gear than try to find supernatural explanations why it does work better than other gear. What is important after all that it works and delivers great images, isn't it?

Best regards

Erik

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borissimo86 Regular Member • Posts: 186
Re: medium format compression

I think that the following article puts all these questions to rest:

http://www.bokehblog.com/photography/post/Medium-Format-vs-Full-Frame-vs-Crop-Sensor.html

Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 2,959
Re: medium format compression

borissimo86 wrote:

I think that the following article puts all these questions to rest:

http://www.bokehblog.com/photography/post/Medium-Format-vs-Full-Frame-vs-Crop-Sensor.html

Hi,

Yes and no. Any movement of the camera changes perspective. So the only relevant case is when the camera is fixed and equivalent focal length is used. Equivalence for 45mm in 24x36 in APS-C is 28-30 mm, not 24 mm. So 24 mm makes for a wider view.

Lens selection makes this kind of comparisons difficult.

The other factor is depth of field. If we shot 45 mm on f/2.8 on 24x36 we would need to shoot 30 at f/1.9. That would give a good approximation. The Zeiss Tuit 32/1.8 would be a good match.

Making a correct comparison is not exactly easy. But, considering the significant cost difference between the systems that effort may need to be taken, as not to mislead potential buyers.

Just to say, I would suggest it would be difficult for APS-C to give 44x33 mm a run for the money regarding image quality. 24x36 vs. 44x33 may be possible.

In the old times it was a bit easier. You bought the camera with a standard lens. On 24x36 it would be a 55/1.7 (or 55/1.4)  and you would shoot say stopping down two stops. Results would be pretty close, especially if used Tri-X on 6x6 and Plus-X on 24x36.

Best regards

Erik

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Arcimboldo Regular Member • Posts: 366
Re: Pinholes

JimKasson wrote:

Paul wrote:

i am not sure i can follow. i know what i can see and i did a side by side between A7RII and fuji GFX the other day and i was honestly surprised of how obvious the difference was between the 2 (pretty similar) formats when capturing a the same angle of view using (obviously) 2 different focal lengths.

using the same focal length on both cameras would obviously create the same depth, but the A7RII file would look cropped, the GFX would show a wider angle. to get the same angle i had to switch to a wider focal length on the A7RII which made the center of same scene appear further away.

i shot tons of files that day and don't keep this stuff. you have tested the gfx in depth and i am very grateful for you testing, i am pretty sure you could easily test this yourself?

i feel like i have tried to say the same thing several times here, to me this is easily visible, the bigger the difference in format, the easier visible.

Maybe I'll do the demo. I have to say when I was shooting 8x10 and 4x5 in the studio, I didn't think twice about taking the same picture with a 300mm lens on the 8x10 and a 150 on the 4x5. The images looked the same to me. I'd sometimes use the 4x5 to get everything right before bringing in the 8x10. Course you'd have to open up the 4x5 two stops to get the DOF the same.

Jim

Exactly my experience when using 4x5, Sony FF, and Olympus MFT. But you keep on reading this thing about larger format producing less wide-angle distortion, see for example this otherwise very nice review on the GFX 23 mm: https://jonasraskphotography.com/2017/04/19/icelandic-inclusion-the-fujinon-gf-23mm-f4-review/.

Also, there seems to be a mix-up of what wide-angle distortion actually is - it's not barrel distortion or perspective distortion (keystoning). Rather it's the distortion of spheres to look like eggs towards the corners in a strong wide-angle shot. This effect depends on the angle of view and the distance from the subject - the larger the angle and the less the distance the stronger said distortion.

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