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02-27-2019, 07:24 AM   #16
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Another article from people who enjoy seeing their words on a screen, but have little understanding of their subject.
From a “needing more light” perspective, no. Medium format doesn’t “need more light”.
A medium format frame needs exactly the same amount of light as a same speed 35mm frame to secure similar exposure.
Interestingly, they assign a thing called an f-stop to lenses, and even more interestingly, if you set a medium format lens to the same f-stop as a 35mm lens, they will project the same intensity of light within the limits of their individual calibrations.
Medium format will give somewhat less depth of field for any given aperture than 35mm, but that is a different conversation.


Last edited by Wheatfield; 02-27-2019 at 09:36 AM.
02-27-2019, 09:12 AM   #17
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QuoteOriginally posted by Silent Street Quote
I witnessed one of these beauties come crashing down onto coastal rocks a few years ago. The owner was ...DEVASTATED. Turned his back, along came a gust of wind and...Chammo was no more...
Eeek!

I actually had a tripod failure with a four-foot fall to a concrete walkway a few years back and know that sinking feeling. Amazingly, there was no damage outside a few paint scratches and a tiny divot in the teak.


Steve

(...memo to self: "Always double check tripod legs"...)
02-27-2019, 11:48 AM   #18
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QuoteOriginally posted by Wheatfield Quote
From a “needing more light” perspective, no. Medium format doesn’t “need more light”.
A medium format frame needs exactly the same amount of light as a same speed 35mm frame to secure similar exposure.
I'm sure you've made, and as a prof/teacher had students make, pinhole cameras. A tiny pinhole camera, let's say one the size of a matchbox, with photosensitize paper inside about 24x36mm in full sun might have an average exposure of 2 seconds. A small pinhole camera (with the same size pinhole aperture) let's say an iPhone box 3x5" which would be the equivalent of something between medium and large format would typically have an average exposure of 8 seconds. And with a shoe box 8x10" size pinhole camera, you'd need an exposure with again, same amount of daylight and aperture, of 2-4 minutes.

From this, wouldn't we agree that the larger the format, the more light or photons is needed?

Another way to think of it is from darkroom experience. The amount of light coming from the enlarger is finite. At the same aperture, it takes approximately/theoretically 4x longer to print a 16x20" vs. an 8x10" because one is 4x larger.
02-27-2019, 01:16 PM - 1 Like   #19
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QuoteOriginally posted by Alex645 Quote
I'm sure you've made, and as a prof/teacher had students make, pinhole cameras. A tiny pinhole camera, let's say one the size of a matchbox, with photosensitize paper inside about 24x36mm in full sun might have an average exposure of 2 seconds. A small pinhole camera (with the same size pinhole aperture) let's say an iPhone box 3x5" which would be the equivalent of something between medium and large format would typically have an average exposure of 8 seconds. And with a shoe box 8x10" size pinhole camera, you'd need an exposure with again, same amount of daylight and aperture, of 2-4 minutes.

From this, wouldn't we agree that the larger the format, the more light or photons is needed?

Another way to think of it is from darkroom experience. The amount of light coming from the enlarger is finite. At the same aperture, it takes approximately/theoretically 4x longer to print a 16x20" vs. an 8x10" because one is 4x larger.
Your ever growing pinhole camera has an ever growing [larger] f/number due to the growing effective focal length. The larger the f/no the less light (photons) per second per square whatever of film plane. If the pinhole area over the focal length squared remained constant then the exposure time should be constant.

02-27-2019, 02:10 PM   #20
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QuoteOriginally posted by Wheatfield Quote
A medium format frame needs exactly the same amount of light as a same speed 35mm frame to secure similar exposure.
Handheld light meters do not have any setting for a format what complies with the statement above, and metering of incident light not only ignores format, but also field of view of the camera. I think that the question should be slightly altered: does MF need more light than 35mm frame when FOV and DOF are kept constant? Accordingly to my DOF calculator 90/4 lens on 35mm gives the same FOV and DOF as 185/9 on 6x7 (in both cases distance to subject was 3m), so the latter definitely needs more light. It may seem contradictory but it's not: the former statement is about density of exposed negative, while the latter applies to constant FOV and DOF.
02-27-2019, 02:13 PM   #21
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QuoteOriginally posted by biz-engineer Quote
While reading about larger camera format, this article The Light Eater: The Biggest Challenge of Large Format Portraiture | Fstoppers caught my attention. I though of getting some clarification and feedback from people having experience with medium format: how practical is the use of a medium format format compared to 24x36 ? Is it truly difficult to use for common use cases? Thank for sharing your thought from experience. I'd be very interested.


That article points out the widely misunderstood concept of photography that is f-stop. A f-stop is a f-stop regardless of format. A medium format “requires more light” not because of the larger size but because of the “slow” lenses. The obvious implication is that full frame cameras do not gather more light compared to crop sensor cameras.

That article also points out that in real world photography, shallow DoF is a problem not a feature that noobs typically go crazy about.


02-27-2019, 02:40 PM   #22
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QuoteOriginally posted by Alex645 Quote
I'm sure you've made, and as a prof/teacher had students make, pinhole cameras. A tiny pinhole camera, let's say one the size of a matchbox, with photosensitize paper inside about 24x36mm in full sun might have an average exposure of 2 seconds. A small pinhole camera (with the same size pinhole aperture) let's say an iPhone box 3x5" which would be the equivalent of something between medium and large format would typically have an average exposure of 8 seconds. And with a shoe box 8x10" size pinhole camera, you'd need an exposure with again, same amount of daylight and aperture, of 2-4 minutes.

From this, wouldn't we agree that the larger the format, the more light or photons is needed?

Another way to think of it is from darkroom experience. The amount of light coming from the enlarger is finite. At the same aperture, it takes approximately/theoretically 4x longer to print a 16x20" vs. an 8x10" because one is 4x larger.
No, what we would agree on is that as you increase the length of the box, you are increasing the focal length, thereby "stopping down" your pinhole camera.
02-27-2019, 02:40 PM   #23
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QuoteOriginally posted by Alex645 Quote
I'm sure you've made, and as a prof/teacher had students make, pinhole cameras. A tiny pinhole camera, let's say one the size of a matchbox, with photosensitize paper inside about 24x36mm in full sun might have an average exposure of 2 seconds. A small pinhole camera (with the same size pinhole aperture) let's say an iPhone box 3x5" which would be the equivalent of something between medium and large format would typically have an average exposure of 8 seconds. And with a shoe box 8x10" size pinhole camera, you'd need an exposure with again, same amount of daylight and aperture, of 2-4 minutes.

From this, wouldn't we agree that the larger the format, the more light or photons is needed?
An interesting idea, but still misunderstanding the problem.

The pinhole camera example fails because you're keeping the pinhole size the same while greatly increasing the effective focal length of the camera. The iPhone box might be 40mm deep, so the focal length is 40mm, but the 8x10 pinhole might be 250mm deep, more than 6 times the focal length of the iPhone box and needing more than 36 times the exposure. Remember that aperture number is related to focal length: a 100mm f/2 lens has a diaphragm diameter of 100/2 = 50mm while a 35mm f/2 lens only needs a diaphragm diameter of 35/2 = 17.5mm.


If large format optical (not pinhole) lenses need longer exposures for the same aperture as a 35mm camera, why did exposure meters like the Weston, Lumisix and others not have a way of calculating these longer exposures when taking an exposure reading? They absolutely did not have such a method because it wasn't needed. An exposure of 1/15sec at f/8 on a Spotmatic F became an exposure of 1/15sec at f/8 on a Hasselblad 500C, 1/15sec at f/8 on a 5x4 Linhof and the same on an 8x10 Deardorff.

If the FStoppers article gives a different impression then they are wrong or you're misreading it.

02-27-2019, 02:44 PM - 1 Like   #24
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QuoteOriginally posted by pentageek Quote
Handheld light meters do not have any setting for a format what complies with the statement above, and metering of incident light not only ignores format, but also field of view of the camera. I think that the question should be slightly altered: does MF need more light than 35mm frame when FOV and DOF are kept constant? Accordingly to my DOF calculator 90/4 lens on 35mm gives the same FOV and DOF as 185/9 on 6x7 (in both cases distance to subject was 3m), so the latter definitely needs more light. It may seem contradictory but it's not: the former statement is about density of exposed negative, while the latter applies to constant FOV and DOF.
A lens on at f5.6 gives exactly the same amount of exposure as any lens at f5.6 regardless of format.
All the link in the op is doing is playing the equivalence game.
02-27-2019, 03:37 PM - 2 Likes   #25
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QuoteOriginally posted by Wheatfield Quote
A lens on at f5.6 gives exactly the same amount of exposure as any lens at f5.6 regardless of format.
All the link in the op is doing is playing the equivalence game.
This is true...sort of. The title of the linked page and this thread are both misleading. The linked article is about a characteristic of large format photography that is obvious to the user during the first excursion with the camera. Actual exposure (EV) is the same as what might work for a small format dSLR* at the same ISO, but exposure times for adequate DOF may be incredibly long.** Razor thin DOF is only cool when it is hard to get. It is a pain in the rear if that is ALL you get at reasonable shutter speeds without addition of supplemental light. Those two sentences summarize the article nicely.

The format does not eat light, per se; instead, the optical reality of going big simply requires smaller apertures to allow adequate DOF for most subjects, meaning less light to the film. There is a reason why Jimmy Olsen's 4x5 press camera had a flash gun. Yes, I guess that is part of the "equivalence game" except that using large format as an example can be quite effective at dispelling error.


Steve

* It is not unusual for large format folk to take use a dSLR to test exposure and composition in a manner similar to taking a Polaroid frame. Amazingly enough, f/8 at 1/8s is the same on APS-C at ISO 100 as on 4x5 shooting TMax 100.

** Notice avoidance of the words "equivalence" or "equivalent".

Last edited by stevebrot; 02-27-2019 at 03:43 PM.
02-27-2019, 03:46 PM - 2 Likes   #26
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....aaaaand another thread goes down the equivalence rabbit hole....
02-27-2019, 05:02 PM   #27
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The trick is how many factors you want to match. I think of my 105/2.4 on my P67 like a 50/1.2 on 35mm because it is a close field of view and a close depth of field at maximum aperture. On the other hand there is something like a two stop difference in maximum light gathering. On the other hand most of my photography doesn't have that many DoF matching requirements, and in those cases--ƒ11 is ƒ11 and on either 35 or 6x7 gives me enough DoF for my shot.

If all you care about is f-stop, they're all the same. but MF lenses don't have as low a maximum aperture, and DoF is smaller for the same aperture because to get the same field of view you need a longer lens, and longer lenses have shallower depth of field.
02-27-2019, 05:18 PM - 3 Likes   #28
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QuoteOriginally posted by Sandy Hancock Quote
....aaaaand another thread goes down the equivalence rabbit hole....
Given this is the medium format section of the site, the rat hole should be quite shallow. The level of expertise is high and most of the users have known for years that their gear is different for a reason and that talk of equivalence is a form of parlor diversion and not of any consequence. At least, I would think that is the case.


Steve
02-27-2019, 05:20 PM   #29
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I quite agree Steve, but an all-too-familiar pattern was emerging
02-27-2019, 11:08 PM   #30
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QuoteOriginally posted by Wheatfield Quote
A lens on at f5.6 gives exactly the same amount of exposure as any lens at f5.6 regardless of format.All the link in the op is doing is playing the equivalence game.
The f number is a relative term: the ratio between the size of the aperture and the focal length, the f number was created to simplify the use of exposure metering independent from format. Although, for the same FoV , the lens focal length will be longer with the larger format, so f/5.6 on a longer FL will actually use a larger aperture diameter. So to keep equivalence of DoF, it looks like large format will almost always require using a tripod for shooting at 100 ISO, but 645 medium format would still be usable hand-help in a lot of cases. Having read somewhere that the 6 cm x 7 cm format was named "the ideal format", I would guess that 6 x 7 delivers high quality image but still being practical (that's my assumption..., I'm not sure about why 6x7 is called "ideal format").

The why I posted here is about how practical medium format is in real life shooting, and when to stop look for larger format depending on what we want to photograph. I mean, if using a heavy tripod is the only way, perhaps we should be aware of it and think twice.
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