Cambo Actar, buy the lens first and the camera later... find out why!

[Theodoros]

The Cambo Actar is a converted Samyang 24mm f3,5 lens.... Cambo has removed the helicoid (so that there is no focusing ability) and the rear part of the lens barrel (with the shift/tilt mechanisms of course) which causes some optical issues due to obstruction of the image circle (as it happens with all Tilt/shift lenses) when the lens is shifted.

What does this means? It means three things:

1. The lens performs considerably better than the Samyang 24mm f3.5 when shifted for the same image circle size as the original lens....
2. The lens has a very wide image circle that would cover even a 54mm x 40.5 image sensor with very well controlled vignetting (but is much better optically towards the edges if one uses an up to 37X49mm image sensor...)

3. (most important) That the lens is fully compatible with all Mamiya 645, P1-XF, Contax 645, Pentax 645 & Leica S cameras if a helicoid with focusing is machined and screwed to the back of it instead of the Cambo mount that is fitted on it as you buy it... Meaning that you can always switch the mount of the lens between your MF camera & your Cambo whenever you like!

How well it would perform is I suppose the next question one would ask.... Well, I guess this is what we are going to discuss here, out of the people that have used it or that have used the Samyang 24mm/3.5 T/S.... I only have experience with the Samyang (when testing for my own Contax 645 camera - finally decided in favour of the better optically Nikkor 24mm PC-E as to use on my Contax) and I can say that the lens should disappoint many when fully open, but it improves dramatically stopped down to f5.6 (I wouldn't hesitate to use it there with MFDB) and is really good if stopped down to f8 & even more so at f11.... f16 is very good too with 6.8μm pixel size sensor of 37x49mm size. More details about its performance later in the discussion when it heats up....

SUGGESTION TO CAMBO: Why don't you make helicoid focusing adapters for the Actar people? A 24mm lens for Leica S, Contax 645, Mamiya 645 & Pentax 645 cameras, even if it can only be used stopped down it should sell 10 times as many lenses if offered at near 1000 price point... and it would be usable on both the view camera and one's MF camera too...

[BobDavid]

It is a great lens. I've ended up buying it for the Actus. Extremely sharp at f/8. Hardly any CA, extremely well corrected for linearity. I intend to write a review on it one of these days.

[torger]

Cambo has a full resolution sample shot (made on A7r-II I think) on their page:

https://www.cambo.com/en/actus-mini/cambo-actus-mini-view-camera/actar-24/

It doesn't seem to be as good as a good copy of the TS-E 24II, but it's certainly not bad and it's fairly small and not too heavy.

[rueyloon]

Are you sure it fits the 645 slrs? I was doing some measurements off the lens diagram and found that at infinity it will hit the mirror.

[Theodoros]

Are you sure it fits the 645 slrs? I was doing some measurements off the lens diagram and found that at infinity it will hit the mirror.

I think I know what you didn't count for in your calculations! The mounting distance of the lens is still the one of the Samyang 24mm f3.5 lens. I'm 100% sure for C645 mounts and (of course Leica S) 95% sure for M645 mount (I don't know how recessed the mirror is inside the M645 mount - but it should be much more than what is needed) and 75% sure for Pentax 645... (which has the most recessed mirror but the longest mounting distance too). Please calculate again for the Samyang mounting distance! 

[Theodoros]

Cambo has a full resolution sample shot (made on A7r-II I think) on their page:

https://www.cambo.com/en/actus-mini/cambo-actus-mini-view-camera/actar-24/

It doesn't seem to be as good as a good copy of the TS-E 24II, but it's certainly not bad and it's fairly small and not too heavy.

Anders, out of the original 24mm f3.5 T-S lenses, (Canon, Nikon & Samyang), if they are used on an FF camera with no movements, the Nikkor is the sharpest, followed by the Canon and then the Samyang... if fully shifted at f8-f11-f16, then Samyang has the most uniform frame (beats the Canon at the edges & corners), followed by the Canon, with the Nikkor third.... but both the Nikkor & the Samyang have their rear element very recessed into the lens barrel and this causes them mechanical issues, as the optics are shaded behind the lens frame... Additionally, the Nikkor has a "flange" before the lens mount that restricts some of its image circle even if not shifted... The Canon has the rear element much closer to the sensor and thus has the least of (mechanical) issues... If one removes the shift/tilt mechanisms, (just like Cambo did) then, both the Nikkor & the Samyang are even sharper towards the edges of the (full) image circle they can exhibit, while the Nikkor even expands its image circle to its full potential.

If now one tries the Canon, Nikkor and Samyang on a view camera with an MFDB on, but with the Nikkor & Samyang "stripped" from their T-S mechanisms & rear part of the lens barrel - no need to do so on the Canon, it won't improve further - one will find that the Nikkor is sharpest across the frame at all apertures, but it has the narrower image circle (it will have the strongest vignetting if used on a 54x40.5 sensor, but it is very sharp across the frame on a 37X49 sensor from f5.6 up to f16 (even usable wide open), the Canon is close in the centre, but only acceptable towards the edges and corners provided that it will be stopped down to at least f8 - better (for edges) at f11 (still 37x49 sensor) and the Samyang has the wider image circle out of all (it will cover a 54x40.5 image sensor easy) and is sharper than the Canon (provided that it is "stripped") towards the edges and corners at f8-f11-f16...

The Canon is the best lens to use for its purpose (meaning T-S with a FF camera) but this is due to its different mechanical design (it can't be converted for use on an MF camera at all), but on a view camera the Samyang is better and the Actar should be even better since it got rid of all the issues that the lens barrel causes to the Samyang...

Now if one decides to convert the Actar or the Nikkor for use with an MF camera and MFDB, the Actar would be better with a 54x40.5 sensor, but the Nikkor would be much better (and with full dedication for full aperture metering, electronic aperture control and full mode compatibility too...) for up to 37x49 sensors at ...more than triple the cost for new, since it needs to be converted for electronic communication with the camera's mount too... That said, the Nikkor can't be used on Pentax 645 at all and I'm not sure if it can, on M645 (until I have access to one as to measure the distances)... but it surely can for Contax 645 and Leica S....

[torger]

Do you talk about the version 1 TS-E 24? Otherwise I am surprised as it would be the first time I hear the Canon is not the sharpest of the three. Version II is a lot better than the first, but there are still some sample variation though. But well, maybe unshifted the others can compete?

[Theodoros]

Do you talk about the version 1 TS-E 24? Otherwise I am surprised as it would be the first time I hear the Canon is not the sharpest of the three. Version II is a lot better than the first, but there are still some sample variation though. But well, maybe unshifted the others can compete?

I'm talking about the TS-E/II lens... As I said before, the Canon is the best lens to use for what these lenses are made for (which of course is for shifts and tilts on a FF camera)... But if the lenses are used unshifted (which is what is best on a view camera because one avoids the problems of the lens frame shading the full image circle that the lens can project)  the Samyang is better at the edges and corners of the full image circle projected In that case, (lenses unshifted) the Nikkor has the sharpest image across the frame, but it still has some shading of the image circle due to a flange that exists near the lens mount... If the Nikkor's rear part of the lens barrel is removed completely (like Cambo has done with Samyang to make the Actar), the Nikkor's image circle widens some more (although not as much as the Canon or Samyang but close.... but it is the sharpest across the frame on a 37x49mm sensor.... The Canon is close for the centre of the image circle and still very good for (what would be) the edges of the 24x36 frame, but the Nikkor is sharp all over on a 37x49 image sensor. Guess what my new 24mm f3.5 Contax 645 lens is....  It will be ready in less than a month! ...and it will work with full aperture metering and electronic aperture control, VF info & full mode compatibility exactly as if it was a genuine Contax 645 lens.... 

[marc aurel]

I'm talking about the TS-E/II lens... As I said before, the Canon is the best lens to use for what these lenses are made for (which of course is for shifts and tilts on a FF camera)... But if the lenses are used unshifted (which is what is best on a view camera because one avoids the problems of the lens frame shading the full image circle that the lens can project)  the Samyang is better at the edges and corners of the full image circle projected In that case, (lenses unshifted) the Nikkor has the sharpest image across the frame, but it still has some shading of the image circle due to a flange that exists near the lens mount... If the Nikkor's rear part of the lens barrel is removed completely (like Cambo has done with Samyang to make the Actar), the Nikkor's image circle widens some more (although not as much as the Canon or Samyang but close.... but it is the sharpest across the frame on a 37x49mm sensor.... The Canon is close for the centre of the image circle and still very good for (what would be) the edges of the 24x36 frame, but the Nikkor is sharp all over on a 37x49 image sensor. Guess what my new 24mm f3.5 Contax 645 lens is....  It will be ready in less than a month! ...and it will work with full aperture metering and electronic aperture control, VF info & full mode compatibility exactly as if it was a genuine Contax 645 lens.... 

Hi Theodorus,

I am sceptical about the claimed superiority of the Nikon and Samyang over the Canon. As Anders remarked - the results of a lot of tests by different people found the canon to be the best among the 24mm shift lenses (and not just because of the superior mechanical design but because of it's sharpness, contrast and lack of CA). Do you have comparisons images that you base that opinion of and that you can post?

Shading by the lens barrel should not affect sharpness levels of a lens at a certain distance from the optical center, just makes it darker. So I do not think that the different use of the lenses you describe would change the general performance.

One other thing comes to mind when the TS-E 24mm L II is used on the Cambo: the lens is designed for focusing by turning the focusing ring. That changes the distance between lens groups. When you focus on the Cambo by changing the distance between the complete lens and the sensor - that might influence the performance of the lens. I don't know if this is the case, but it's a possibility.

With the Cambo you can mix different ways of focusing:
1. You can set focus on the TS-E to infinity (or any other focusing distance as a starting point) by using the focusing ring on the lens. AND THEN you can set your desired focusing distance by changing the distance between lens and camera on the Cambo.
2. You could also set the Cambo to a fixed distance between lens and sensor which is identical to the one in a Canon DSLR. AND THEN use the focusing ring on the lens.
Would the sharpness be different? Has anybody who owns a Cambo ever tried something like this? That would be quite interesting for me, because I thought about using the Cambo with my TS-Es. And it would be fun to use Cambos focusing mechanism. But only if that does not affect performance.

Regards -
Marc

[Theodoros]

Hi Theodorus,

I am sceptical about the claimed superiority of the Nikon and Samyang over the Canon. As Anders remarked - the results of a lot of tests by different people found the canon to be the best among the 24mm shift lenses (and not just because of the superior mechanical design but because of it's sharpness, contrast and lack of CA). Do you have comparisons images that you base that opinion of and that you can post?

Shading by the lens barrel should not affect sharpness levels of a lens at a certain distance from the optical center, just makes it darker. So I do not think that the different use of the lenses you describe would change the general performance.

One other thing comes to mind when the TS-E 24mm L II is used on the Cambo: the lens is designed for focusing by turning the focusing ring. That changes the distance between lens groups. When you focus on the Cambo by changing the distance between the complete lens and the sensor - that might influence the performance of the lens. I don't know if this is the case, but it's a possibility.

With the Cambo you can mix different ways of focusing:
1. You can set focus on the TS-E to infinity (or any other focusing distance as a starting point) by using the focusing ring on the lens. AND THEN you can set your desired focusing distance by changing the distance between lens and camera on the Cambo.
2. You could also set the Cambo to a fixed distance between lens and sensor which is identical to the one in a Canon DSLR. AND THEN use the focusing ring on the lens.
Would the sharpness be different? Has anybody who owns a Cambo ever tried something like this? That would be quite interesting for me, because I thought about using the Cambo with my TS-Es. And it would be fun to use Cambos focusing mechanism. But only if that does not affect performance.

Regards -
Marc

Marc... It's perhaps my English, but I never said that the Samyang or the Nikkor are better than the Canon if one compares the lenses for what they are designed for... Actually, I said quite the opposite! What I've said, (and it stands with all that have tried it), is that the Nikkor is even sharper with the lenses unshifted (on a 35mm FF image camera) and that the Nikkor is even sharper if one removes the rear part of its barrel (including the tilt/shift mechanisms) and use it unshifted on a larger sensor (33x44 or up to 37x49)... it also expands its image circle a bit when the lens is converted. The Samyang is no where near the other two up to f5.6, but at f8 it is sharper than the Canon at the edges of the frame if fully shifted... The Canon is indeed very good, but on a sensor that is larger than 33x44 (i.e. 39x49 or 54x40.5), one will find that the Samyang is sharper at the edges and corners (not at the center) at all f8, f11 & f16.... Usually, this wouldn't matter, but if one uses the lens on an MFDB camera (the Samyang can be converted as to be used on an MFDB camera - the Canon not) it would matter....  More than that, if the Samyang is also converted by one removing the T/S mechanisms and the rear part of the barrel (like Cambo has done with the Actar) as to replace it with an appropriate shorter one, its edge and corner performance (with MFDB used as light sensitive area) improves further....

All the above, has nothing to do with the original lenses...., since nobody would buy a 24mm f3.5 t-s lens to use it unshifted (where the Nikkor is the sharpest) or since the usual movements used are limited, but it's wrong to conclude that on a larger than FF image area the situation would stay the same.... Honest, the Actar (or the Samyang converted) will make a good lens for MF cameras (but only after f8) and the Nikkor (at triple the cost - double for one to buy the lens new and another half of that to convert it) will make a very sharp 24mm for MF cameras (with sensors up to 37x49mm)!

EDIT: All the above apply with lenses set to infinity....

[Theodoros]

Ahhhh... forgot to mention that the Canon 24mm f3.5 TS-EII will work very well indeed if converted for Leica S body (much better than the Samyang to that size of image circle...) but still the Nikkor will be sharper on the Leica-S at all apertures, never the less, the Canon will leave very little to Complain about on the Leica S, while the Nikkor would probably "pass" to the demands of one that expects "Leica S glass" kind of performance.

[BobDavid]

The Actar is an f/8 lens. And at f/8, it is stunning.