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Compatibility of digital body with old lenses


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Showing 1-25 of 49 posts in this discussion
Initial post: 18 May 2011, 19:23:38 BST
andysollitt says:
Hi, I've got an old Nikon F-401 which uses 35mm film. In order to upgrade to digital and still be able to use the lenses from the old camera, which digital body do I need?

Posted on 18 May 2011, 20:24:07 BST
X says:
If you can live with the fact that film camera lenses were made to bring the light only onto a surface, so pretty well any angle of incidence works, while digital camera lenses must bring the light into individual electronic receptors, so the angle of incidence pretty much has to be 90, you may like the results you get. I didn't.

One of the main manufacturers has produced a sensor where the light receptors are inclined away from 90 degrees according to their distance from the centre, so the light gets right the way in each receptor.

That is such a cute trick it's probably done by Fuji, Ricoh or some other nest of mad scientists. I forget.

Keep it simple: buy lenses designed for your camera...

Over to Graham...

In reply to an earlier post on 19 May 2011, 00:08:06 BST
Last edited by the author on 19 May 2011, 00:09:18 BST
Hi Ed,
Do I recall that we had a mature discussion of this very subject two or three years ago?
Well you are right - there are different requirements for film and digital sensors. Digital sensors work best if the incident light is normal to the sensor, even though each pixel has a micro lens to minimise the effect. However, there is no way to eliminate this because the edges of the sensor will always receive light at an angle unless the rear element were at infinity.
I have both digital and legacy film lenses and there is no appreciable difference between them when it comes to the position of the rearmost element even though the theory suggests that the more retrofocus the better. I have read that in practice the digital lenses have better coatings on the rear elements and better light deadening at the rear, It is notable that legacy lenses are often decribed as being more prone to flare.
My suggestion is that lenses should be judged on performance - an exceptional legacy lens may be as good or better than a cheap digital lens, and it may be obtainable cheaply secondhand. It's concievable that it was designed to have low flare anyway. I'm sure that digital lenses benefit from new technology in the use of plastic lens elements, aspherical surfaces and it must help that the APS-C sensor does not need as big an image circle. That in itself seems like a good reason to prefer digital lenses - if funds allow.

However, I believe that Andy wants to buy a Nikon dSLR which his lenses will work with, retaining AF, if possible.
Over to the other Graham................

Posted on 19 May 2011, 01:21:00 BST
Last edited by the author on 19 May 2011, 01:54:02 BST
Graham H says:
Andy, I use both modern lenses and old "legacy" lenses from my film Nikons (F90X) and they both work fine.
The gentlemen who've replied above know far more about photography than I do, but I know a little about Nikons so I'll have a bash for you!
I short, take for example my excellent (and cheap!) Nikon 50mm F/1.8 prime lens. It was designed back in the days of film and is still 100% compatible with digitals. And still available new. Likewise the amazing 80-200 F/2.8. Great with both 35mm and digital.

You don't mention which Nikon digital you're looking to go for, but from the nature of your question I'm guessing it will be one of Nikon's "DX" format DSLRs. Basically, this is pretty much everything under two grand!
The "Crop factor" of these smaller size sensors effectively means that your lenses will be "Longer" in the focal length than the ones designed for film or for Nikon's "FX" cameras (Which start with the D700) which have a sensor the same size as a 35mm film frame (Or as near as makes no odds).
In short: Yes, they'll work fine. Your F401 was autofocus, so if you want autofocus to work on your digital Nikon you'll need a D90 or upwards.
This camera can run Nikon's current AF-S lenses (AF equal Auto Focus, "S" means that the lens has Nikon's "Silent wave motor", in other words, the AF motor is built into the lens and the camera merely provides power and instructions to it)

However; the D90 also has the small tab poking out of the lens mount and a motor built into the body which allows it to run the older AF-D lenses too. Nothing below the D90 can do this. Which is why I have a D90.
If you're not bothered by autofocus then you can use any of the current Nikon DSLRs with any of the autofocus lenses from any era. But you'll have to twiddle the ring (Oo-Er!) and focus them manually.

The old manual focus lenses are a different kettle of fish, because they provide no metering information to the camera. I don't know a whole lot about those because all my manual focus film kit is from other makers, mainly Canon and Olympus, so if you need to know about the really old stuff I'd check here:

http://www.kenrockwell.com/nikon/compatibility-lens.htm

In summary: You want the lenses from your F-401 to work on a digital and still autofocus? You need a D90.

Hope this helps!

Graham (2)

Posted on 19 May 2011, 09:03:58 BST
X says:
If I were paranoid I would complain about the two Grahams victimising me like that. But I'm just a soul whose intentions are good...

In reply to an earlier post on 19 May 2011, 09:55:09 BST
Last edited by the author on 19 May 2011, 09:56:26 BST
Ed,
Just because you're not paranoid...........................
To be fair I did concede that you were technically correct. It's just that some old lenses seem to have been made, by accident or design, without many of the flaws which are undesirable for digital use.
The Beercan is a fine lens but you need to watch out for flair. The 50mm is good too. Those are the only legacy lenses I use, really.
If you go to Dixum.com you see every Sony/Minolta lens rated for a variety of indicators. It is clear that some lenses designated "digital" are no better, and sometimes worse, than some legacy lenses. Ergo cheap modern glass may not be as good as expensive old glass. I think that a legacy prime will probably exceed the performance of a cheap kit zoom. Proof of pudding and all that.
We're all old enough to have attained a bit of cynicism so do we really think that all manufacturers re-engineered all their lenses for digital - other than a fancy multicoating on the rear element and some additional matt black paint? I think that where they did they would have made savings eleswhere anyway - maybe on aperture or use of plastic bayonet mounts and so on.

In reply to an earlier post on 19 May 2011, 14:51:56 BST
Last edited by the author on 19 May 2011, 14:58:53 BST
This should amuse you Ed,
I have a plan to graft a Meyer Trioplan lens onto the front of my dSLR for an experiment. I can set it on T to keep the shutter open and use the camera shutter. We shall then see how much progress has been made in the last 75 years.

Posted on 19 May 2011, 15:56:56 BST
X says:
Graham:

Oh,

ha-

ha!

Posted on 19 May 2011, 17:13:30 BST
Graham H says:
Oh, nothing I wrote was intended to contradict you Ed! You know far more than I do about all this sort of thing.

I can just speak as I find, and without a shadow of a doubt the best, sharpest and most impressive looking results I've ever had from the D90 have been when using the old 50mm F/1.8 prime that was originally designed and marketed for Nikon's 35mm film cameras.

Posted on 19 May 2011, 17:34:04 BST
X says:
Time for some tea, Graham. I shall toast you in Sri Lanka's finest.

In reply to an earlier post on 19 May 2011, 18:21:29 BST
Ed,
You are such a purist. If only I had such focus!

Posted on 19 May 2011, 20:53:16 BST
X says:
Graham: Now what did you misspell to end up with "purist" and "focus"? My teddy will have his work cut out when I solve that, I fear.

In reply to an earlier post on 23 May 2011, 14:04:16 BST
Stan says:
Digital v Film lenses;
Is it not the case that a digital sensor is smaller than a 35mm film frame and that because of the effective lengthening of 35mm-eqivalent focal length, the full aperture of the lens is not used? Surely (surely . . .?) this will reduce the problem of over-oblique light on peripheral sensors of a DSLR?
On the other hand, are there any remaining film buffs who have tried 'digital' lenses on a film SLR? Do they suffer from vignetting I wonder.
Maybe someone, sometime, somewhere will invent a slightly concave sensor and then finish the job off with barrel/pincushion correction with in-camera software!
Incidentally, since virtually all lenses are now DSLR lenses, are their designated focal lengths 35mm equivalent or are they actually to the narrower angle that the old lenses need mental correction for?
John

Posted on 23 May 2011, 16:46:18 BST
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In reply to an earlier post on 23 May 2011, 17:58:22 BST
Stan/John
The quoted focal lengths are the actual focal lengths, not just for 35mm but for any format. They are invariant and are an intrinsic property of the lens. It's just that a 50mm focal length lens used with an APS-C sensor would give a similar sized image to a 75mm focal length lens on a 35mm camera. All the optical qualities remain the same its just like cropping the image smaller on an APS-C sensor.

Posted on 23 May 2011, 19:45:37 BST
X says:
Graham: It will not surprise you to learn that I tried to write a reply similar to that, but was incapable of formulating it clearly... Well put!

In reply to an earlier post on 23 May 2011, 20:08:27 BST
andysollitt says:
Thanks Graham. I looked at secondhand D90s and they quote 'activation' numbers. Is there a maximum usage, or figure which indicates when the D90 has ended its useful life, and if so what is the maximum figure? That way I hope to estimate how much life is left in the body offered for sale.

Posted on 23 May 2011, 22:10:57 BST
Last edited by the author on 24 May 2011, 13:25:56 BST
Graham H says:
Hi Andy,

Yes, there is a firmware function in the D90 (And I believe most Nikons) which stores a running total of shutter activations over the camera's life. If you're looking at advertised examples with actual activation counts stated I'd say it's a good sign, because only a Nikon specialist will know how to access that and have the hardware to do so (As far as I know!)

Nikon (also as far as I know) test the D90 shutter mechanism to 150,000 cycles, but this is not an absolute. I've never really worried about it to be honest.
Nikon don't say what the 150,000 activations signify either. Is that 150,000 to mechanical death, or 150,000 before wear and tear causes some timing inaccuracies? Or 150,000 and still working fine? I have no clue. Nor am I that bothered really.
I've read of Nikons with over 1,000,000 activations that are still going strong. There are plenty of other things that can kill a camera long before the shutter mechanism dies. Heat, dust, moisture ingress, even good old "Dropping the bugger". Anyway, how much is a new shutter mechanism fitted? £200 or so? If you use it enough to wear out the shutter then I'd say you'd got your money's worth!

Stan: using Nikon's DX (Cropped sensor) format lenses on a film or full-frame camera creates images with dark corners, as you say. If you cropped the pictures though they would look fine.
I was relieved that Dr G responded to that one as he's far more scientific than me! I can tell you want the pictures look like because I shoot with those lenses, but he's far better than I at explaining the whys and wherefores behind them.

In reply to an earlier post on 24 May 2011, 01:00:44 BST
Last edited by the author on 24 May 2011, 01:16:01 BST
I've been thinking about the query as to whether the full aperture is used by a sensor smaller than the format for which the lens has been designed. It's one of those things which sounds plausible yet which cannot be true. It can't be true because if the lens coverage were a function of the aperture then the use of a small aperture would cause vignetting (dark corners) which would worsen as the aperture lessened.
However, it is true that the edges of the image are less well resolved than the centre so if you effectively crop the image by using a smaller sensor (or film size - several roll film cameras have masks to take 8, 12 or even 16 shots) you will get better performance edge to edge of the smaller image.
In an SLR, in order to fit the mirror in, the lenses are designed to have retrofocus. For instance, a simple single element 20mm lens would have to have its centre 20mm from the sensor - but the mirror box is about 40mm deep. Therefore the lens has to be designed to be physically further away than its focal length and additional lenses are used to straighten the rays to focus at a point further away than the overall focal length of the lens. Only telephoto lenses over about 60mm to 75mm will not need retrofocus. The complication of a 16mm to 105mm zoom can only be imagined - hence the numbers of elements.
A lens designed for an APS-C sensor will have some sort of restriction of the diameter of some of the lens elements to eliminate the peripheral rays which are not required. Smaller diameter elements are easier to correct optically and hence cheaper as well as lighter and smaller. Nevertheless, I believe that some digi lenses will nearly cover a full sized sensor but edge darkening (vignetting) may well occur. Of course the pic could be cropped to remove these vignettes and one of the benefits of the large sensor would be lost. Isn't this done automatically on certain full frame Nikons if a small sensor lens is attached?
The smaller sensor does not require the more oblique rays of light from a 35mm lens but to get the same size image on an APS-C sensor you need a shorter focal length. Those oblique rays will not come back though because the rear element will still be the same distance from the sensor because of the retrofocus. In addition, the legacy lens (full frame) may have more retrofocus (bigger mirror box) so perhaps they show an advantage there too. I read that some Canon digi lenses for the 1.5 ratio sensors cannot be used on full frame because the rear element has been mounted closer to the focal plane and would be hit by the mirror.
I wonder if some legacy lenses which were a bit iffy actually work better on digital because the rough edges are cut off?

Some of the mirrorless cameras like the Panasonic G micro 4/3 cameras take advantage of the lack of a mirror box to reduce the retrofocus and hence the overall length of the lens. I imagine that this means that there are rays which are more oblique than we see in a dSLR. Some of these pancake lenses are 20mm mounted about 20mm from the sensor instaed of 30mm - 40mm. I wonder if, or by how much, this causes fall off of IQ at the edges of a micro 4/3rds frame?
Just how much effect these different optical paths have in practice I have no idea.
Sorry if this is a bit of a dogs dinner but it's hard to write a long tract in the little slot provided when you are used to revueing stuff on a full page

Posted on 24 May 2011, 11:20:20 BST
Graham H says:
Dr G:

Yes, you're perfectly correct. If you attach a Nikon DX (APS-C) lens to a full-frame body then the camera uses only the area of the sensor that a DX format camera would have.
Of course, you'd be an idiot to shell out for a full-frame (FX) camera then use DX lenses, but it's nice that they will at least work if you find yourself with one.

In reply to an earlier post on 24 May 2011, 13:01:27 BST
Stan says:
Not sure if I'm making comments on one or several submissions but;-
1) I'm not sure that varying the aperture of a lens by its iris diaphragm is the same as reducing the area of the image receptor (film or reduced size digital).
Someone may help . . .?
2) Retro focus; surely ( ? ) the light path through the lens to the image sensor is direct when the mirror is lifted out of the way and the sensor/film is exposed. The retro focus considerations are relevant only when the light is diverted via the flipping mirror* through the pentaprism or pentamirrors to the viewfinder screen.
* I recall, from the early sixties, that the handbook to a Pentax SLR warned users to "keep your fingers off the flipping mirror". Useful advice probably more emphatic than the writer realised!
Thanks to contributors both knowledgeable and not. Amazing how the train of thought is focused even when two layeople change views! I'm learning a lot!
Stan

In reply to an earlier post on 24 May 2011, 14:33:44 BST
Stan,
1) The aperture is irrelevant to whether vignetting occurs for all practical purposes. I thought you raised it as a possibility when you said "that because of the effective lengthening of 35mm-eqivalent focal length, the full aperture of the lens is not used?". Did I make a mistake and take you too literally? If so then my apologies. Perhaps you wrote that in the sense that the full coverage of the lens was not used? This is correct - you are cropping off the peripheral margins of the image which is more difficult to correct optically.
2) Retrofocus has nothing to do with the mirror or indeed whether you have a mirror. Retrofocus is where the optical centre of the lens is further from the plane of focus (film plane or sensor) than the effective focal length of the lens.
When the mirror is deployed the focus is merely diverted to the focusing screen within the viewfinder instead of the film plane/sensor (hence 'reflex') - it can't affect the focal length though because the mirror is flat.
No doubt the warning from Pentax was to stop the OCD types from trying to clean the mirror, which is very delicate.
A simple short focal length lens (say 10mm) would have to be placed so close to the sensor/film plane that the mirror of an SLR would have to be locked up. To retain the operation of the mirror a reverse telephoto construction is added to the rear of the lens so it can behave as a short focal length lens whilst maintaining a sufficient gap between the sensor and the rear element to fit the mirror mechanism in. That is retrofocus.
This would be so much easier with a diagram.

In reply to an earlier post on 24 May 2011, 23:02:25 BST
i guess this has allready been corrected but the D50/60/70/80 have the focus motor built into the camera body and work well with all of older AF lenses so not just the D90

Posted on 24 May 2011, 23:38:16 BST
Last edited by the author on 24 May 2011, 23:40:06 BST
Graham H says:
True. But they're all getting on a bit. In fact, a lot. 2005 as I recall.
I think Andy was originally looking at what he could get new.

Posted on 25 May 2011, 00:34:48 BST
Stan says:
Response to Dr G Austin;
Thanks for clearing my confusion over retro-focus. I should've known that! My remaining confusion is now the distinction between 'optical centre' (point?) and 'optic axis' (line) or is the optic axis, when viewed from a position normal to it, the optical centre?.

My amusement at the old Pentax reference to the "flipping mirror" was the fact that "flipping" is/was used in polite circles here up-north in UK as a euphemism for f***ing! A meaning, no doubt not realised by a 1960s Japanese handbook writer. However, short of calling it a "hinged" or "moving" mirror I don't know what alternative there is although Nikon simply refer to "the mirror".

Sorry if there is another version of this message but I seem to have lost the first draft somewhere in the ether!
Thanks again for correcting me
Stan
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