Some unresolved mysteries

[willem_aart_van_dorpen]

<p>Let me start with telling you that, at this moment, a large format camera is out of reach for me. I'm using a Canon dSLR with a 24mm tilt/shift lens. While that is a pretty technical setup and does pretty much everything I need, I want to know everything about large format camera's and lenses, that's why I started this topic.</p>

<p>After wandering through the internet for a few days, I collected a few questions that have remained unanswered to me. I never went to a photography school of some sort, and there isn't much written for beginners like me about this subject. Well, let's dive into the questions, if you don't mind:</p>

<p>1) What's exactly the difference between medium format and <em>digital</em> large format when using a digital back? Is it just the ability to make shift movements with the greater part of the large format camera's, in combination with the larger image circle of the lenses?</p>

<p>2) What's the difference between a medium format camera and a digital large format camera that has no ability to make shift movements? They offer the same functionality and end result, right?</p>

<p>3) Are you able to use pre-digital era lenses on a modern digital large format camera? Are these just as good as digital lenses in general?</p>

<p>4) Does 'Digitar' reference to 'digital'? What's the difference between a Digitar lens and another large format lens? Is the image circle smaller? Are they compatible with 4x5" film?</p>

<p>5) Are you able to shoot film with, let's say, a Cambo Wide RS? The lenses have the same large format image circle I suppose, they should cover the film right?</p>

<p>6) Are the focal lengths shown in 35mm equivalent? Does a 24mm large format lens have the same focal length as a Canon 24mm?</p>

<p>7) What are the differences between a large format and medium format lens? Is it just the image circle?</p>

<p>I would be very thankful if anyone of you can answer (some of) these questions :). I would love to buy a large format setup, unfortunately the prices of digital backs are sky high.</p>

[leicaglow]

<p>Hi Willem, Here are <em>my </em>responses, based on what I know...</p>

<p>1. Yes, mainly movements. There are not many LF digital backs (I think BetterScanning, and maybe one or two more).<br>

2. Mainly lenses, I would guess(!). A MF system uses proprietary lenses and mounts. A LF system can use any LF lens with the right board.<br>

3. Yes, but just like Canon or Nikon has made huge improvements in coatings and construction, so have the LF lens manufacturers. The difference really depends on the shooting situation.<br>

4. Yes. Yes. Only if the image circle is big enough. But they are generally used on a specialized camera using a smaller sensor, like a Sinar P3, or Arca Swiss, for example.<br>

5. I don't know about the Cambo, but most of the others I've seen allow for a film back to be attached... usually with an adapter for a special 2x3 or a Hasselblad back (for example). They are not cheap. In fact, with these systems, nothing is cheap.<br>

6. No. Lenses are truly 35mm or whatever. They cover a certain image circle, and you have to check to see what each will do, but usually 2x3.<br>

7. Again, the fact LF is not proprietary, and can be mounted to any camera with the right lens board. BTW, you can buy special lens boards to mount a Hasselblad or Mamiya lens on a LF camera, but many will only cover the smaller image circle, which is fine if you are mating the lens with a smaller film size back.<br>

Finally, I would buy a regular LF camera (something like a Sinar, for example) that allows adding digital backs. It will be a bit larger, but they are all pretty awkward to set up. </p>

[kelly_flanigan1]

<p>Here I run two old obsolete 35 and 50 megapixel digital LF scan backs from circa 1996 and 1998. The are mostly used indoors to shoot artwork; or odd thick objects that will go into my 36" wide color scanner. All of these LF backs are what today are called cropped backs. Mine are Phase One and have a 7x10cm scan area; the Better lights are about this too. I have never heard of a full frame LF scan back.</p>

<p>1) Here the reason I use a LF digital scan back is just to have a giant digital file to make a copy of artwork. I use to shoot transparencies and scan them; the cost and delays with no local lab got expensive. The reason I got a LF digital back is the local E6 got flakey and died. Very few if any LF digital scans I do for artwork has any shifts; if it is it is for lighting or shadows.<br>

The some shift work is for tabletop shots for products or scale models; a very minor amount of shots are shifts.</p>

<p>2) When I got into LF digital; LF had the bigger megapixel scans compared to MF; thus a MF back was only 4 to 8? megapixels back then and the 1996 4x5 back was 35 megapixels. One got a LF back because it was a higher megapixels; one could gather more details.</p>

<p>3) one can use older non digital lenses on a digital back; here that is *about all* I have ever use. My back's have a big fat 12 and 13 micron effective pixels; thus the lens requirements are modest. I shoot artwork with a Schneider Componon 135mm F5.6 on a 4x5 Speed Graphic</p>

<p>4) A SCHNEIDER Digitar is a trade name for lenses that are for high resolution digital backs; ones that are tighter than my mine in pitch. With a higher megapixel back the pixel pitch is narrower; thus a better lens can help.</p>

<p>5) No cambo here</p>

<p>6) NO EXACT ANSWER. One has two different aspect ratios. If one was making say 30x40" prints or 40x40" the short side of 35mm governs. A swag is that 35mm is about 1" tall (not .945) and 4x5 is 4" tall; thus a 4x factor to shoot a 30x40" or 40x40" print. Thus a 24mm on a full frame 35mm would be like a 96mm on a 4x5 camera; if one is shooting a 30x40" or 40x40" print.</p>

<p>7) MF lenses are shorter since the format is smaller. A normal for 6x6cm MF is about 75mm; and it is about a 150mm for 4x5</p>

[dan_south]

I recently posted a comparison of using large format versus Canon TS lenses. It might be useful to you since you are

coming from a Canon TS background.

 

http://www.photo.net/digital-camera-forum/00XEWe?start=20

[bob_salomon]

<p>Rodenstock published an excellent white paper on the differences between digital and analog and how the requirements for digital lenses differ from analog lenses. If you are in the USA we can still mail you a copy. It is no longer on their web site but a newer paper on the advantages of perspective correction in camera vs in Photoshop is now available for downloading. Both papers were by Dr. Walter Schoen. If you would like the copy just email me a mailing address and we will send it to you.</p>

[indrek_r_nkla]

<p>7) I think a major difference between the lenses of MF and LF especially important on wide-angles is the design. The MF lenses are retrofocus as the rigid body and the mirror do not let the lens to protrude close enough to the sensor/film surface. LF lenses do not need to address this issue and tend to have therefore better IQ all over the image circle. Or at least should have.</p>

[willem_aart_van_dorpen]

<p>Great replies, thanks a lot!</p>

<p>@Bob Salomon: Unfortunately, I'm not in the USA. What did you expect, reading my terrible English ;-)?</p>

<p>It makes sense why some people choose for large format, instead of a proprietary medium format system. Let's hope digital backs get a bit cheaper, film is not my cup of thea.</p>

[beamoflight]

<blockquote>

<p>Great replies, thanks a lot!<br /> @Bob Salomon: Unfortunately, I'm not in the USA. What did you expect, reading my terrible English ;-)?<br /> It makes sense why some people choose for large format, instead of a proprietary medium format system. Let's hope digital backs get a bit cheaper, film is not my cup of tea.</p>

</blockquote>

<p>Sorry, but you can wait till you drop dead before true large format digital backs become affordable - <em>they don't even exist at this point of time if we discount the scan backs</em>. Except scanning backs, which almost cover 4x5, the only digital "LF" backs are in fact <strong>NOT</strong> LF backs, but MF backs fitted to LF camera's, and even those cost enough to buy a car!</p>

<blockquote>

<p>film is not my cup of tea</p>

</blockquote>

<p>Well, in my opinion, it should be if you seriously want to get into LF. I have the strong feeling, you don't know what you are getting into... Operating an LF camera can be quite a hassle (but I love doing it - well at least most of the time ;-) ), and setting up and taking a single(!) shot can take anywhere from 10-60 minutes.</p>

<p>Really, if you don't care for film (it is not that difficult, learn develop it yourself, it's fun), than cut the crap and buy a tilt/shift lens for your DSLR. It won't brake your bank, and it will do "more or less" the only thing you really seem interested in.</p>

<p>And if you do consider 4x5 film, an Epson V700/750 at a scanning resolution of 2000 ppi (pixels per inch) should deliver stunning digital files of about 8000x10.000 = 80 Mpixel resolution.</p>

<p>Of course, nothing beats printing analog in your own darkroom... (not that many here will agree, but I don't care, it's my cup of tea ;-) )</p>

[beamoflight]

<p>Ah well, I see you already have a T/S lens... well, stick with it, or buy a lens-baby for more creativity.</p>

[willem_aart_van_dorpen]

<p>A large format camera with a medium format digital back is my ideal setup because it allows me to make shift and tilt movements, with much greater quality and flexibility than my TS-E 24mm lens. Also, I'm able to see directly what I've shot and to make adjustments as I go.</p>

<p>If digital camera's didn't exist, I would have never got into photography I think ;-). Does that make me an inferior photographer? Maybe. It's not really important to me.</p>

[kelly_flanigan1]

<p>HI Marco;<br>

I would like to clarify a 2 points you made that I differ with:</p>

<p>RE "Except scanning backs, which (2) almost cover 4x5, the only digital "LF" backs are in fact <strong>(1)NOT</strong> LF backs, but MF backs fitted to LF camera's, and even those cost enough to buy a car!"</p>

<p>Correction(1): Many LF digital 4x5 scan backs are NOT MF scan backs. I am not sure why you got that idea from. Chip type backs are even tiny. MF ones are often sub MF in size too.</p>

<p>The LF scan 4x5 backs I use here scan a 7x10cm area; this is way bigger than MF's size. They use a standard 4x5 film holder size; but they are thicker; and the sensor was never made for MF usage; thus your statement is misleading.</p>

<p>What you may be thinking about is there were a few LF back variants that long ago in the smaller Megapixel sizes were similar in name and features for the MF and LF versions.A Phase One Brand called I think the Studio Kit once had a LF and a MF version. The LF version had the giant 4x5 back like mine; the MF back had adapters but I think used the same software and tether cord and interface.</p>

<p>Correction(2): NO LF scan backs ever made even came close to covering 4x5; they are all truncated in scan/capture area; ie what today folks call "cropped". There are no "almost cover 4x5 LF digital backs"; except in Hogwarts! :). The Phase ones here scan a 7x10cm area. A 4x5 sheet is maybe 3.75 by 4.75 usable; that is a 9.5 by 12cm area. One really with these backs is just capturing a 61 percent of the area of a practical 4x5 shot. 61 percent is not almost; more like a decent crop. 61 percenty is from 7*10/9.5*12=0.61 The Betterlight scan backs are cropped about the same too. One gets about 60 percent of a 4x5 frame.</p>

<p>To All; when I compare a direct scan with the 50 megapixel back to a scan of a sharp 4x5 scanned with a flatbed; the 50 megapixel direct scan holds more details. This is with a V700, V500, 2450 etc scan. This includes the added area that the full 4x5 has compared to the cropped 4x5 digital ie 7x10cm. Thus here if I shoot a detailed wall with the 4x5 50MP back and with a 4x5 transparency; the flatbed scan picks out less details; even if one lets the map fill the entire 4x5 frame.</p>

<p>With a tighter pitch brand new Betterlight 4x5 back like their top 8K-HS; it shoots a non upsized shot of 8000x 10600 pixels for 18k. Its scan area is 72x96mm; ie not full frame 2.83" by 3.78"; ie it is less than an old 3x4 camera shoots. The higher unit the 10K-HS is sold out ie gone; so is a 6000-HS unit. About nobody buys these types of backs anymore; their useage peaked 5 to 10 years ago; like dialup modems.</p>

<p>Willem; a MF back in LF camera will allow tilts and swings; but a MF back is cropped. Thus with this type of rig one needs lenses a really shorter than what one uses on a film MF camera; that fit on a LF body. That is one reason the Digtar "digitaL" lens series has such sort lenses; ie 28mm F2.8 for Cambo for 2400 bucks. These are used with "chip" sensors on camera backs; non scan types usually. The Digitars are 24 to something like 180mm.</p>

<p>Probaby none of this stuff will ever be inexpensive ever. The market is very tiny.</p>

[beamoflight]

<p>I wasn't commenting on the quality of your work or whether you are a good photographer or not, neither do I pretend to be one myself, and especially not "just because I shoot LF" or so... I leave that to others to judge.<br>

But I was just wondering if you have any idea what these digital backs actually cost... Unless you are doing this completely professional and are already some succesful studio or architectural photographer, or have some extremely well paid job covering the costs of your photo hobby, the prices are just prohibitive.<br>

Sure, I'd like one too, but that's not going to happen anytime soon...</p>

[beamoflight]

 

<blockquote>

<p>Correction(1): Many LF digital 4x5 scan backs are NOT MF scan backs. I am not sure why you got that idea from. Chip type backs are even tiny. MF ones are often sub MF in size too.</p>

</blockquote>

<p>Kelly,</p>

<p>I think you misunderstood me. I fully agree with you that LF digital scan backs are no "MF scan backs". In fact, although they may have existed at some point in time, I have never seen images of a "MF scan back".</p>

<p>What I was referring to is that, except for the existence of LF scan backs, there is no equivalent of a full frame MF digital "one-shot" back, a digital back the size of a 4x5 inch negative with a similar sized sensor that can take a photo in one ago, without a slow scanning action.</p>

<p>Again, that would require a huge 4x5 inch sensor... Considering some MF backs (and maybe all?), already need active sensor cooling using a build in fan, I guess a 4x5 sensors cooling fan would be the size of a WWII Spitfire propellor... ;-)</p>

<blockquote>

<p>Correction(2): NO LF scan backs ever made even came close to covering 4x5; they are all truncated in scan/capture area; ie what today folks call "cropped". There are no "almost cover 4x5 LF digital backs"; except in Hogwarts! :).</p>

</blockquote>

<p>I never had a really close look at the scanned area size advertized by the manufacturers of such scan backs, but immediately take your word for it. Actually, this makes the thought of a true "<strong>full frame LF</strong> digital back" appearing anytime in the future, let alone for an affordable price, even more a complete phantom... if even the existing scan backs do not cover it, nor ever did...</p>

 

<blockquote>

<p>To All; when I compare a direct scan with the 50 megapixel back to a scan of a sharp 4x5 scanned with a flatbed; the 50 megapixel direct scan holds more details. This is with a V700, V500, 2450 etc scan. This includes the added area that the full 4x5 has compared to the cropped 4x5 digital ie 7x10cm. Thus here if I shoot a detailed wall with the 4x5 50MP back and with a 4x5 transparency; the flatbed scan picks out less details; even if one lets the map fill the entire 4x5 frame.</p>

</blockquote>

<p>Might well be, a flatbed is not the equivalent of an Imacon or drum scan. 50 MP from a high end scan back or MF digital back, is a lot for sure, although a 100 ISO film scanned on a drum scanner might squeeze out a little more... but not much. Than again, how much more does one really need???</p>

<blockquote>

<p>Probaby none of this stuff will ever be inexpensive ever. The market is very tiny.</p>

</blockquote>

<p>Agree!</p>

 

 

[massimo_de_cristofaro]

<p>Hi.<br>

I would like to add a consideration that wasn't made (as far as I read here...)<br>

The main difference between analog and digital LENSES is not only the focal leght (for the smaller area of sensors).<br>

Much more important is the fact that sensors must be illuminated by vertical rays.<br>

So the desing of lenses is strongly different, arranging a kind of "retrofocus" we could say; very important in wide angles.<br>

Instead, analog lenses, could hit the film diagonally and still give enough light to impress: but in extreme cases there were the "central filters" to arrange the same amount of light in the whole area.<br>

I never tried, but using a 45mm XXL on a large digital sensor could produce strong vignetting due to inclination of rays, even if the image circle could be much wider than sensor's surface.<br>

Another issue is that a good big LF scanning back takes many minutes to build the image file, so it is useful only in landscape, architecture, still life etc.<br>

I always like these "fights" between different sides of technology.<br>

The strongest importance of digital is the fact that images are pratically ready for publishing, with also CMYK channels and so on.<br>

In fine arts instead, there are many problems after shooting: printing chain could be a very hard job...</p>

 

[profhlynnjones]

<p>I won't write you a complete scientific paper but here is the essence:</p>

<p>Digi sensors require that the light rays be perpendicular to the face of the sensor. Therefore lenses in which field flateners are not designed in, lose anywhere from 30% to 40% of the radial light rays. Certain camera maker used as an advertising message, "You don't need new lenses, use the lenses that you have always used for film"! As a result, digi cameras often said, "5MPm effective, 3.4MP or some similar piece of information. The first digi camera that only lost 1 or 2% was Olympus, the next was Sony, and then Tamron which not only designed cameras for digital sensors but did so in both typical sensor sizes. At that point the big N and the big C realized that they had to change their design philosophy.</p>

<p>The reason for the incredible expense of wide angle lenses has to do with the ability in retrofocus to have a great wide angle and still be able to turn the light around so that is is directly straight ahead of the sensor. Sensors are like a microscopic honecomb.</p>

<p>Lynn</p>

[massimo_de_cristofaro]

<p>I totally agree with Lynn :)</p>

[beamoflight]

<p>Well, always funny how reality can overtake you:<br>

<br /> http://www.dpreview.com/news/1008/10083101canonlargestsensor.asp<br>

<br /> 8x8 inch(!) digital one-shot CMOS sensor developed by Canon... That is almost 8x10 Large Format, although the current wafers don't allow the full 8x10, but of course, 4x5 no problem...<br /> Also a similar discussion about LF digital sensors in this Photo.Net thread:<br>

<br /> http://www.photo.net/large-format-photography-forum/00X7Qd?start=0<br>

<br /> Still, price will be as phenomenal as the sensor I guess, if it ever makes it to a commercial product for the professional photographer. Also wonder about the cooling of the thing... as I already pointed out some MF size sensors use / need active cooling.</p>

[massimo_de_cristofaro]

<p>Ok: this Canon wafer could be useful in photo documentation of Greenland melting glaciers... if the sensor could produce enough heat to keep the computer going</p>

[kelly_flanigan1]

<p>That Giant Canon Sensor has a pixel pitch of 160 microns and it is 1.6 Megapixel.<br>

<br /> http://techon.nikkeibp.co.jp/english/NEWS_EN/20100902/185407/<br>

<br /> My 1996 Phase One Scan back is 35 Megapixel with a 14 micron effective pixel pitch.</p>

<p>Maybe with time they can get that pixel pitch down on a giant sensor. It looks like the big guys goal was just to gather a lot of light with ultra low light video</p>

[kelly_flanigan1]

<p>160 microns is 0.16mm ; say 1/6 mm for a slide rule.</p>

<p>That is about what makes a good contact print.</p>

<p>If one could line up magically; one could get 3 line pairs per mm on the sensor. Ie 3 blacks and 3 white bars in 1 mm.</p>

<p>3 line pairs per mm</p>

[beamoflight]

<p>Hmm, well, it seems there is already something almost equivalent to a 4x5 inch LF digital sensor, and this one does have resolution...:</p>

<p>http://www.fairchildimaging.com/products/fpa/ccd/area/ccd_595.htm</p>

<ul>

<li><strong>9216 x 9216</strong>(!) full frame CCD array</li>

<li>8.75µm x 8.75µm pixels</li>

<li><strong>80.64mm x 80.64mm</strong> image area</li>

<li>100% fill factor</li>

<li>Non multi-pinned phase (MPP) operation</li>

<li>8 outputs (4 on each side)</li>

<li>Readout noise less than 30 e- at 100MHz (25MHz x 4)</li>

</ul>

<p>That's about 85 Mpixel, not bad... Aerial camera product though at this moment made by Fairchild Imaging.</p>

<ul>

</ul>