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Author Topic: Are there any special lenses to get non-croppe image with digital backs?  (Read 6095 times)
BJL
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« Reply #20 on: November 15, 2010, 03:54:38 PM »
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liac,

    the only real issue is whether you can get the focal length you need to provide the angular field of view you want with a given sensor size: the fact that a lens might project an image larger than is needed by the sensor is not in itself a problem, so long as flare problems are avoided. If for example the new Pentax 55mm lens gets a job done with the 44x33mm sensor of the 645D, it hardly matters whether that lens is producing an image that is only good over an image circle of 55mm diameter (just enough to cover that sensor diagonal, so "non-cropping" or "44x33mm full frame") or if it is instead producing an image that is good over a circle of larger diameter, say 70mm or more so as to cover 645 format (so that the image is "cropped" --- shock! horror!).

In fact:
- Most Mamiya lenses for the RB67 and RX67 have image circles significantly larger than needed by 6x7 format.
- Many LF lenses used with 4x5 format have image circles significantly larger than that format.
- The new Pentax 55mm MF lens, although designed primarily for its new 44x33mm format digital camera, apparently covers the full 645 format. (Perhaps Pentax expects to sell a good number of them to users of existing Pentax 645 film cameras.)
- Most telephoto lens optical designs naturally produce an image circle larger than needed (about 40-50º coverage is natural for the basic optical designs, even for super-telephotos intended to work with a far smaller angular coverage) though this excess is often reduced significantly by baffles in the lens or by the narrowness of the opening at the back of the lens.

But in none of these cases do I hear people complaining that the lenses are suffering from a "crop", and demanding new lenses of the same focal lengths but with smaller image circles, so as to "fix" this "problem".


And as to getting the "right focal length": yes MF lenses systems are often missing the focal lengths hat would be needed to achieve much-wanted FOV choices with used with DMF backs, and wide-convertors attached to the front could provide those focal lengths, but they have a rather bad reputation for optical problems, as discussed above. Wide-convertors seem to be a tougher design that the tele-converters you are discussing.

I suspect that in the already high-priced world of DMF, most users would prefer a small percentage increase in the total gear budget to "do it right", by getting lenses that have the needed focal length to start with. ... Or at worst are a bit shorter than needed, so that one needs to crop a bit to the desired FOV, given how many posters complain about recent MF sensors having more than enough pixels!
« Last Edit: November 15, 2010, 03:57:43 PM by BJL » Logged
liac
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« Reply #21 on: November 15, 2010, 04:40:13 PM »
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I don't know why people use not full-frame sensors and are satisfied with it. I used fuji s3 pro with usual 35 mm lenses and could not shoot in rooms with lack of space. So i bought a lens specifically designed for cropped sensors. And what i got: greater sharpness, wide-angle, ability to shoot inside of houses. So if i use 36x24 sensor of H5 for example, i will get the same problems. In order to correct this and to get the ability to shoot inside i will have to use the 1.5 or 2x converter. Converter is equal = to wide-angle lens in quality, it may be considered as part of the lens without degradation to quality and it does not bring more distortion than the wide-angle lens with the same angle. I don't know why people are not using this effective tool. The guy who showed me his converter on pentacon is world famous photographer and if he uses converter it is worth it I am sure.
I would buy canon mark II instead of a cropped MF sensor back but I still want to have the ability to shoot 6x6 cm at least with film. What makes me angry with the film is that it requires an expensive scanner which i cannot afford either.
I want to sell fuji, rolleiflex camera and epson scanner which i have and to buy hasselblad with one or two lenses and a digital back. So my budget will be 2500-2700$. What can i buy on ebay with this amount?
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yaya
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« Reply #22 on: November 15, 2010, 04:54:59 PM »
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In order to correct this and to get the ability to shoot inside i will have to use the 1.5 or 2x converter. Converter is equal = to wide-angle lens in quality, it may be considered as part of the lens without degradation to quality and it does not bring more distortion than the wide-angle lens with the same angle. I don't know why people are not using this effective tool. The guy who showed me his converter on pentacon is world famous photographer and if he uses converter it is worth it I am sure. I want to sell fuji, rolleiflex camera and epson scanner which i have and to buy hasselblad with one or two lenses and a digital back. So my budget will be 2500-2700$. What can i buy on ebay with this amount?

I'd love to see this "effective tool" and the results you get from your new $2,700 camera, no pun intended

Yair
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eronald
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« Reply #23 on: November 15, 2010, 05:08:30 PM »
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I'd love to see this "effective tool" and the results you get from your new $2,700 camera, no pun intended

Yair

Yair,

 Aren't we being snippy today? Smiley
 Don't forget I get to buy you lunch or dinner next time you're in Paris.
Edmund
« Last Edit: November 15, 2010, 05:10:11 PM by eronald » Logged

Edmund Ronald, Ph.D. 
Dennis Carbo
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« Reply #24 on: November 15, 2010, 06:05:53 PM »
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I dont think you could even get a H20 for that price, even the Old Kodak DCS 16mp backs are going for 3-4k on e-bay. The 6 MP Leaf Velo (dont remember how to spell it sry) made some nice quality files, bet you could find one with a Hassy V for 3k or so. 

I think I would look for good a Used DSLR and Lens with that Budget in mind though, more bang for the buck if you are on a budget  IMO

D

This just in......Kodak DCS Back on Ebay.. Buy It now $2495.00 
« Last Edit: November 15, 2010, 06:11:45 PM by DENNISCARBO » Logged
Christoph C. Feldhaim
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There is no rule! No - wait ...


« Reply #25 on: November 16, 2010, 03:00:47 AM »
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Or get a cheap 8x10 field camera, one lens and make contact prints ....
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liac
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« Reply #26 on: November 16, 2010, 03:57:14 AM »
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That's too big, heavy and requires film. I will buy one of the following H5, H10, H11, H20 or equivalent.
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yaya
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« Reply #27 on: November 16, 2010, 04:26:27 AM »
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That's too big, heavy and requires film. I will buy one of the following H5, H10, H11, H20 or equivalent.

I still don't understand how are you planing to get wide angle with any of these backs on a Hassy...
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liac
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« Reply #28 on: November 16, 2010, 04:28:41 AM »
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I will use 2x or 5x wide-angle converter.
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yaya
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« Reply #29 on: November 16, 2010, 04:58:40 AM »
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I will use 2x or 5x wide-angle converter.

Do you have a link or a picture of one of those handy?
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JonathanBenoit
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« Reply #30 on: November 16, 2010, 06:12:00 AM »
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Are we talking like a 14mm lens on a 35mm dslr equivalent?
I said this before - for interiors, I cant see the need for anything wider than a 35mm lens on a 48x36 sensor, or a 24mm lens on a 35mm dslr.
In my opinion, anything wider doesn't usually provide realistic results. When photographing interiors, accuracy is very important.

Sounds like you should stick with whatever you are doing. Even if you find a wide angle solution to your liking, you still will lack the ability to use rise/fall. Might as well just stick with the canon and TS lenses.
« Last Edit: November 16, 2010, 07:30:42 AM by JonathanBenoit » Logged

ondebanks
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« Reply #31 on: November 16, 2010, 07:01:30 AM »
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Moreover, this linear distortion takes place with objects located close to the camera but it does not apply to distant objects.


It's not generally true to say that it "does not appy to distant objects". Distortion curves in optical data sheets are usually presented for infinite objects. Depending on the optical system, distortion may be better or worse with decreased object distance. Have a look at http://toothwalker.org/optics/distortion.html .

Certainly, looking back to photos I took years ago with that front-of-lens converter on my Minolta, there are gobs of rectilinear barrel distortion for relatively distant objects - such as a window frame at the other side of a large room.


I wonder if you shoot the starry sky with fisheye will you get any rectilinear distortion? Probably not, coz all the stars are so far from us that no perspective distortion could take place.


I've done this; I love to do it - see the attachment below. You get severe rectilinear distortion - of the coordinate grids which we use to describe stellar positions. But of course you cannot see those. You get no visible distortion because the stars themselves are point sources, not linear ones. But even if the image has no visibly distortable content, the lens projection is still distorting like hell! If the quarter-phase moon was in the shot, for example, it would not be reproduced with a straight-edged terminator.

Again, when you say "will you get any rectilinear distortion? Probably not, coz all the stars are so far from us that no perspective distortion could take place", you are clearly confusing perspective and rectilinear distortions. They are completely unrelated.

[As a side issue: one can argue that the way that a fisheye renders the celestial sphere is actually a lot close to the way that the eye sees it. The scale magnification in the corners of a rectilinear ultra-wideangle shot stretches constellations and the angular relationships between stars in a visually odd manner. That's the price for keeping lines straight, when projecting a large portion of a sphere onto a plane sensor or film.]


I will buy H20 some day and make pics with converter on to show if there is any distortion. Probably I need not 2x but a kind of 1.5x converter to get full-frame with minimum distortion for close objects. If anyone can make such pics right now that would be great.

I'm not saying that it cannot deliver good results - just that I am doubtful based on my past experience. I am genuinely interested in how this converter would perform, especially at wide lens apertures. Maybe they've got better over the years. Could you point us to a link for the type of converter you're thinking of getting?

Ray
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pegelli
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« Reply #32 on: November 16, 2010, 07:42:26 AM »
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I don't know why people use not full-frame sensors and are satisfied with it. I used fuji s3 pro with usual 35 mm lenses and could not shoot in rooms with lack of space. So i bought a lens specifically designed for cropped sensors. And what i got: greater sharpness, wide-angle, ability to shoot inside of houses.

Just get yourself a Sigma 12-24, that's a full frame lens that is still pretty wide angle on a crop sensor.
So it's not by definition that a full frame lens cannot be wide angle, only the choices are limited.
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pieter, aka pegelli
liac
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« Reply #33 on: November 16, 2010, 08:10:41 AM »
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Anyway i do not need very wide-angle and fisheye. I prefer creating panoramas by stitching multiple files into one in software.
I need a converter which would have the factor opposite the crop factor of the sensor, no more. I am sure it will not give any visible bending linear distortion. It may give some stronger perspective which will only add positive features to the shot. This is probably not desirable for commercial shots when a close-up is shot but for art photography is good.
This "converter" solution will save me much money I guess. There are many of them sold on ebay. I need to know the filter thread size on the hasselblad lens to buy a suitable converter. I definitely know there are converters for medium format lenses coz i saw such when visiting my friend owning MF pentacon six camera.
I don't know if there are converters for hasselblads or if the pentacon's converter is suitable. Probably, they can be modified for hassy. Another way is to buy wide-angle lens for hassy and it automatically becomes a standard lens for the cropped sensor.
I saw some old hassy models sold at 600$ if you are lucky. The other negative thing is that some cheap digital backs require tethering to PC. I will have to buy a small laptop, a belkin firewire hub and ask a local electrical engineer to build a kind of "portable mains" for powering the belkin hub. I think this solution is possible within 2700$ budget.
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liac
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« Reply #34 on: November 16, 2010, 08:15:07 AM »
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The milky way by the way does not look like bended or distorted.
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liac
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« Reply #35 on: November 16, 2010, 08:17:59 AM »
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Can i install that sigma lens on hassy?
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ondebanks
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« Reply #36 on: November 16, 2010, 08:21:59 AM »
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The milky way by the way does not look like bended or distorted.

That's because I framed the shot so that the MW is running through the centre of the frame: Rule 1 of fisheyes! "Lines radiating from the centre of the field remain straight. All others are bent".
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ondebanks
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« Reply #37 on: November 16, 2010, 08:23:24 AM »
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Can i install that sigma lens on hassy?

Not if you want to get even moderately distant objects in focus. The thicker Hassy body will act as a built-in extension tube. No small-format lens will do for anything but closeups when mounted on a MF SLR.
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ondebanks
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« Reply #38 on: November 16, 2010, 08:25:41 AM »
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Can i install that sigma lens on hassy?

You would also have to get a Hassy with a focal plane shutter - the 2000 or 200 series. None of the 500 series or H series would work - no shutter.
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liac
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« Reply #39 on: November 16, 2010, 08:32:04 AM »
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There are some adapter rings with glass allowing to use M42 thread lenses on Nikon mount bodies. Are there any adapter rings to use 35 mm lenses on MF. Theoretically nothing prevents from building such.
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