Can we use a film camera lens (conventional) on a digital SLR where a telecentric lens is optimal (current)


Link Posted 01/02/2015 - 09:12
I thought I would start up this topic because increasingly I am seeing dialogue on Pentax User, regarding using older conventional Film lenses on Digital Cameras.

It seem a "given" in some posts that traditional older film lenses can be used on a digital DSLR without any issues, which is simply not correct and in the case of wide angle lenses it is arguably a "no,no" regardless of the quality of the wide angle film lens being mounted on a DSLR.

It must be said however, to avoid distracting commentary that their will be exceptions but they are very, very rare exceptions

There is a link below to a very good technical paper that might be useful to read in order to expand the subject a little.

It is a subject I have had a great interest in for several years, so much so that having thoroughly studied the science / optical engineering and technical aspects, and carried out controlled tests using numerous top drawer film lenses on digital cameras (many times) I have adopted a general rule.

1. We should avoid using wide angle film lenses (non telecentric) on digital cameras but can use some top quality long telephoto film lenses

Based on test images the conclusion regarding Digital Cameras can be further refined ;

a. Only dedicated telecentric (digital) lenses should be used below 150mm and particularly in the wide angle range (shorter than 50mm) non-telecentric conventional (film lenses) are not usable if a good digital photo is the requirement ( when isn’t it).

b. In the case of longer focal length particularly above 200mm non-telecentric conventional (film lenses) can be useful and at the extreme telephoto lengths the problems of colour fringing , CA and poor colour rendition that arise in the wide angle range can diminish to negligible proportions

The basic differences in conventional and telecentric lenses:
Modern digital lenses transport parallel light rays in a collimated form from the front element to the sensor
Conventional film lenses (as a rule) transport light rays such that they converge on to the film plane
However not all older lenses were “non-telecentric)

Preamble from the Technical Document “linked below; High Resolution Image Sensors and Lens Performance-

The recent development of high quality multi-megapixel image sensors has revolutionized every aspect of image capture, processing and display. However, for many photographers, both amateur and professional, the transition from silver halide film to silicon-based sensor arrays has not been entirely seamless.

One area where the differences between film-based and digital photography have been especially confusing is with regard to lens performance. After all, if I have a lens that gave me great images on my film SLR, it should work even better on my digital SLR, right?

Not necessarily. This article attempts to clarify some of the lens design and image sensor design issues that can be critical for digital camera performance.

Hopefully after reading this, you will be able to better understand why some lenses work better with digital cameras and what to look for in a digital camera lens.

See the following link which explains High Resolution Image Sensors and Lens Performance in more detail

All comments would be welcomed


Link Posted 01/02/2015 - 09:59
Link has a dot at the end. This causes an error. Just remove the dot in your browser.
I'm inclined not to bother looking at this, because it is an tiny concern compared to just getting out and taking good pictures. But I'm curious, so I'm going in!
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Link Posted 01/02/2015 - 10:10
Whilst it's true that older wide angles will not be telecentric designs, that doesn't mean that we can't use many of them with perfectly satisfactory results.

In terms of mounting and the physical connection of Pentax lenses, we can assume that almost all Pentax lenses can be used on the DSLR range. I would not discourage anyone from doing this, because some of the lenses prove to still be quite excellent. We are also using only the centre of the FOV of these lenses, so that helps.

I'd also mention that several of our best current lenses are in fact from the film era - the 50mm f/1.4, the 31mm, 43mm and 77mm Limited lenses.....these last three still out perform most current telecentric designs.

The other thing to think about is the intended purpose of a lens. Even if we had a really "bad" lens, it just might be the perfect portrait optic. But there are no really bad Pentax lenses.

I think in the case of the Pentax range, we don't have too much to worry about.
Best regards, John


Link Posted 01/02/2015 - 10:13
Yep. Not at all concerning.
I've recently bought a (fairly) wide angle film lens for my digital 645 and it performs just fine. Stars at extreme edges display a certain amount of chroma, but only when pixel peeping and certainly not a concern for the image as a whole, as the important bits are never near the edge.
It is worth remembering that film lenses are invariably designed for larger image circles than the digital sensors so the problem areas lie outside the cropped sensor. This is the case even on the 645 system.
edit: sorry, posts overlapped
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Last Edited by Darkmunk on 01/02/2015 - 10:16


Link Posted 01/02/2015 - 10:18
OK, so now for some Pixel Cross Talk !

I think its long been known and understood that modern lenses, like our DA range, are somehow 'optimised' for the digital sensors that they are designed to work with, and thanks Daroni for providing that informative document which really details the science behind it. It explains some of the issue relating to colour rendition and fringing that we often see when using older lenses.

I'd be cautious though in trying to draw too strong and definite conclusions though .... I find your 'rules' above about not using any wide angles, but only telephotos, as really counter-productive and unhelpful overall. We don't choose and use lenses based exclusively on scientific factors, we base our choice on a range of common sense and practical considerations ...

Not the least is the cost / performance ratio! Many older lenses deliver such a massive bang per buck today that to dis-regard them would be ridiculous and short sighted. I have no doubt that both my SMC A 28 and 50mm primes, and my SMC F35-70, will display some of the negative characteristics referred to in that document, when used on a DSLR. I am aware of small amounts of fringing in normal lighting, and higher amounts in backlighting where contrast is also affected ..... but the sheer quality, visual impact, sharpness and pleasure of using them, plus the huge amounts of all this they deliver for the price, vastly outweighs my concerns over the fringing or any colour issues.

In practice the only lens where I've had trouble correcting a colour issue is with the A28mm in strong backlighting conditions with the light directed mainly into the lens ... here I've had purple / yellowy tones that have proved hard to correct. But in all other conditions this and the other film era lenses perform beautifully, and I'd be mad to not use them.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver


Link Posted 01/02/2015 - 10:27
Thanks for the post and link.

Whilst I understand the physics, in the real world I've seen far too many great results from film-era lenses on digital bodies of all marques to worry about this.

I would just try the lens, and if you like the results, job done.


Link Posted 01/02/2015 - 10:49
If the cap fits!....... Wear it!

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Pentax K-1 + K-5 and some other stuff



Link Posted 01/02/2015 - 19:39
I haven't looked at the link because I don't need a paper to tell me which lenses I can use on my DSLR. I've had zero problems using wide-angle lenses on digital, or any other old film lenses for that matter. Some are better than others, same as modern designed-for-digital lenses, but they have to be checked on a one-by-one basis.
Pentax hybrid user - Digital K3, film 645 and 35mm SLR and Pentax (&other) lenses adapted to Fuji X and Panasonic L digital
Fan of DA limited and old manual lenses


Link Posted 01/02/2015 - 22:05
Some of my favourite lenses are the film era ones

I don't doubt the science behind the information above, however, the proof is in the image so to speak

I find 28mm lenses particularly good, both vivitar and Pentax versions, my tokina 135mm is also very good so whilst the science will spew out many long words and labels so to speak we must view the images and make up our own minds in my opinion

John as well as others have made valid points

Sometimes it is easy to get caught up with the technicalities and miss the point which has to be the images taken not the technical terms in the background otherwise we will all spend many hours trying to understand the demosaicing algorithms of the modern raw file etc

Valid points made but the proof is that many old lenses are great on dslrs


K10D, K5 plus plenty of clueless enthusiasm.

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Link Posted 01/02/2015 - 22:43
Can we confirm that the telecentric lens design is actually being used in the newer APS-C focussed lenses from Pentax?


Link Posted 01/02/2015 - 22:57
Thanks Daroni, It's interesting to see the physics behind 'optimised for digital'. In practice I haven't had any noticeable fringing or similar problems e.g. with my FA24-90 which gets (or used to get, it tends now to stay on the film camera) a fair amount of use at the widest setting, as well as the A24 which is excellent on the rare occasions that I use it. The worst fringing I have had has been with the DA17-70 with bare twigs against a bright sky, overexposed to bring out the colour of the tree.

Re. John R's point about only the centre of the FOV being used, I wonder if the phenomenon referred to is more noticeable when the sensor is the same size as the film?
K5IIs & ME Super with FA24-90, DA17-70, DA55-300, misc old primes; Fuji X20.


Link Posted 02/02/2015 - 14:55
It has been very interesting to read everyone's comments regarding this topic and as always there is some real wisdom and firm opinion coming through.

I most certainly understand the value of the conventional lenses and have quite a collection of Canon, Pentax and the independents, some of which are used when appropriate to image requirements.

Most of them were purchased as professinal spec lenses at the time and some of them can still "hold their own" in specific applications.

Whilst (as an engineer) my first consideration when purchasing anything is the technical spec' and performance data I am the first underline that in some cases the technical performance data can be startlingly good on some of the more venerable lenses we all "keep".

Also it is clear to me that outside of technical imagery , like all photographers I do consider the artistic and aesthetic elements of photography as being at least equal too if not more important than the technical aspects in some branches of the art of photographic imagery and that has a bearing in weather to part with or make an older lens redundant.

I have been heavily involved in all branches of macro photograpy over the years, particularly in technology/technical areas of my work and I still use a manual focus 100 mm Pentax Macro from the eighties alongside two state of the art digital macro lenses I have used extensively in recent times.

In black and white, technical applications it is superb and preferred to the newer lenses, but when it comes to high magnification, high contrast colour images I reach for one of the newer macros dependent on focal length.

As regards older telephotos, several months ago I sent a couple of sample shots over to John Riley to get his experienced opinion on them; they were taken with a Tokina 400mm ATX telephoto ( F4.5) which I bought some years ago, and I wad seeking John's opinion as to how the Tokina ATX compared to a 500 mm Sigma I was thinking of buying.

I had previously undertaken numerous comparisons to my DA*300 and DA* 200 and whilst the Tokina lens did't match the two DA* lenses it was "was ok" at optimum aperture and shutter speeds in ideal lighting, in fact in some of those it was impressive.

Regarding wether the Sigma would give me a big advantage over the Tokina in the field ; Based on critical comparison (on screen and printed,cropped enlargements) that I undertook, sample images from the Sigma, in no way overshadowed the Tokina and hence I sought a second opinion;
Johns opinon was that the Sigma was crisper and has better overall feel, adding that he had also used the Tokina 400mm and although was good, it's not as good as the Sigma, underlining that to be fair, we'd expect that as the Sigma is considerably more expensive.

I eventually decided the extra expense for the Sigma was not justifiable in this case

As regards using older zooms and wide angles, I also on occasions, still use a very "long in the tooth" Pentax 28 - 105 which at the longer end is still acceotabke particularly for BW landscapes so like everyone else I have some "keepers" I am not eager to part with

I think John Riley's comment on FOV in this topic thread is highly relevant to the discussion (conventional vs telecentric lenses) and also might explain the reason why conventional wide angles are considered by the lens experts to be more prone to issues when used on DSLRs ; which technically might in turn relate to the much wider convergence angle of rays passing through the more pronounced lens curvatures of the conventional wide angles.

Conversely it might also be why the flat field correction on macro lenses lessens the effect of covergence angles when using a conventional macro lens on a DSLR.

The narrower convergence angle on telephoto is considered to be the main advantage when using conventional telephotos on DSLRs and these aspects all have associated relevance to Johns comment on FOV and only using the centre of the image.

What is also interesting is to consider the issue of FOV, convergence angles when using a conventional lens on FF digital; the coventional lenses might be less useful in FF as the effect of the convergence angle will could be more acute at the edge of the enlarged FOV.

Finally, if a pro photographer has a selection of Zooms / Primes suited to his/ her work then it would be unlikely that a non- ideal lens would be chosen over a state of the art telecentric lens when critical quality is necessary; it would introduce some degree of unwanted degradationI would think and could become somewhat more conspicuous when cropping or enlarging ?
(other peoples wisdom would be appreciated)

Finally I close by mentioning the different lens coating technology of new lenses vs older lenses which is very interesting, moreso if you images are commisioned or being provided for a customer, ask any wedding photographer ?

This is another topic for another time, I think

Anyway, thanks very much for all contributions which, whilst always providing a fresh view also provide a shared learning experience for all and so far this topic has provided such learning for me.




Link Posted 02/02/2015 - 15:11
I think that, again, any serious photographer, including a Pro wedding or any other type , will simply look at the usefulness, reputation, cost and then actual image output in making any lens choice. If an old film era lens delivers the goods for professional work then it will get used. PP work will be needed for lenses of all ages, it may just be different things, whether a little more CA removal for one or a little more distortion correction for another.

Where I can see an obvious benefit for a professional, or indeed anyone shooting in bulk generally, is where modern digital optimised lens offer in-camera auto corrections for CA and distortion. This will cut down on PP work and is very practical, and not available on older lenses in general. But then again, it only applies to camera Jpegs, so again, maybe not significant for professionals?
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 02/02/2015 - 15:40


Link Posted 02/02/2015 - 18:57
I can't see why a wedding tog wouldn't use golden oldies like the FA50, 43 or 31. I can't see them using old MF lenses for reasons of customer perception and needing to work quickly and efficientlly, though!


Link Posted 02/02/2015 - 18:59
For wedding photography I think the most important thing is silent auto focus and focus speed.

For press work modern gear is essential.

Once you get Into art photography then older lenses bring a different aesthetic to the craft. I still have some old manual focus lenses that I use for personal work that modern lenses just don't offer and this can be different type of bokeh to different colour rendering.
PPG Wedding photography Flickr
Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

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