Mount strength


MrCynical

Link Posted 24/04/2011 - 01:00
Something in a thread about the Bigma made me wonder: how heavy a lens can the mount on our modern DSLRs bear without support? Expecting the camera to bear the weight of a Bigma or similar is probably a good recipe for a snapped-off K mount, but what about the fair few lenses (the DA*60-250 and Sigma 180mm Macro spring to mind) which come in at about 1kg or so? Where do the folks out there with heavy lenses draw the line between lenses which can just be carried on the camera, and those which require special measures such as a strap attaching to the lens tripod socket?

Don

Link Posted 24/04/2011 - 01:53
you're doing it wrong....
you mount the camera to the tripod, unless the lens is heavier than the camera, in which case you'd wanna mount the lens to the tripod...

the mount is definitely strong enough to hold the weight of the camera...
as a general rule if the lens comes with or has optional lens collar with tripod mount..... using that is your safest bet.
Fired many shots. Didn't kill anything.
Last Edited by Don on 24/04/2011 - 01:57

Smeggypants

Link Posted 24/04/2011 - 04:39
My DA* 50-135 is about the limit on lenses I would attach where the camera is mounted on the tripod using the camera's tripod mount.

My Sigma 135-400 has a tripod mount on the collar and I always use that. I'd never hang it off the camera when the camera is stuck ion the tripod. Far too heavy.

I'm working on getting a K mount version of this one btw.



[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Last Edited by Smeggypants on 24/04/2011 - 04:40

alfpics

Link Posted 24/04/2011 - 15:39
at smeggy
Andy
Andy

Dangermouse

Link Posted 24/04/2011 - 16:44
I'm guessing that processing the plates for that involves an indoor swimming pool and a few mops to agitate the developer? Then find a handy crane to use as an enlarger...
Matt

Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.

Smeggypants

Link Posted 24/04/2011 - 18:21
Dangermouse wrote:
I'm guessing that processing the plates for that involves an indoor swimming pool and a few mops to agitate the developer? Then find a handy crane to use as an enlarger...

And that was just the APS-C model. Many peeps were whinging that they wanted a Full Frame version!
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

MrCynical

Link Posted 24/04/2011 - 19:25
I was more meaning for handholding: whether supporting the lens's weight with one hand (or using a lens-attaching strap like the Rstrap) is essential rather than having the lens 'hanging' from the camera. If I were using a tripod and the lens had a tripod collar I'd always use that for balance if nothing else.

Algernon

Link Posted 24/04/2011 - 20:43
Most lens mounts are only held on with 3 or 4 small screws anyway. There was an uproar in the 70's when Canon replaced their breech mount held with 4 screws with a lighter one using just 3

I use a Tokina 400mm lens that hasn't got a mount on it without any problems.

I don't think the force is all that high. If you can pick the lens up by the K mount using just your forefinger and thumb with the lens horizontal there can't be much force. If the lens gets bashed against something.... that's a different story.
Half Man... Half Pentax ... Half Cucumber

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

Algi
Last Edited by Algernon on 24/04/2011 - 20:45

johnriley

Link Posted 24/04/2011 - 20:45
Pentax lens mounts use rather more than three screws - five is the norm.
Best regards, John

Algernon

Link Posted 24/04/2011 - 20:59
johnriley wrote:
Pentax lens mounts use rather more than three screws - five is the norm.

Quite right They must have money to burn Ha! Ha! Olympus use 3 as well. The 400mm Tokina f/5.6 M42 I have only has 3 on the lens mount. I can pick it up and shake it about by the end and I don't think there is an awful lot of force involved. Screws especially high tensile are quite strong. The average guitar string is tensioned to about 25/30 lbs continuously plus more when its being bent/pushed.
Half Man... Half Pentax ... Half Cucumber

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

Algi

pgweber

Link Posted 24/04/2011 - 21:28
When my K10D + 55-300 jumped out of my rucksack and hit the ground, it was the lens that gave way. 3/5 screws snapped out of the lens body behind the mount. The camera held tight onto the metal mount.

Incidentally, one of my batteries now seems to not hold its' charge as well as it used to- possibly the one in the K10 at the time of the accident.

Therefore I feel the camera mount is pretty robust.
Peter

Pentax K5
Pentax DA 18-55 Mk1, 50-200 (Samsung), 16-45, , 55-300, 35 f/2.4
Pentax MZ6 + FA28-90, FA50 f/1.4, M 50 f/1.7
Tamron 80-210mm & 28mm

giofi

Link Posted 24/04/2011 - 21:41
MrCynical wrote:
I was more meaning for handholding: whether supporting the lens's weight with one hand (or using a lens-attaching strap like the Rstrap) is essential rather than having the lens 'hanging' from the camera. If I were using a tripod and the lens had a tripod collar I'd always use that for balance if nothing else.

I would always have one hand holding the camera's grip and the other one holding the lens, even with lighter ones.
Giorgio

Pentax Photo Gallery
Last Edited by giofi on 24/04/2011 - 21:42

Dangermouse

Link Posted 24/04/2011 - 22:10
I don't think the number of bolts is as important as their tensile strength, and that of the part they're screwed into. Remember that you can hang a load of over three tons on a single bolt perfectly safely (the bolt being thicker than your thumb, but still!)

I would be more concerned about flexing in the lens or mount causing unreliable performance with fewer screws, unless the mount was made from thicker, stronger material in order to prevent this.
Matt

Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.

Don

Link Posted 24/04/2011 - 22:29
Algernon wrote:
Most lens mounts are only held on with 3 or 4 small screws anyway. There was an uproar in the 70's when Canon replaced their breech mount held with 4 screws with a lighter one using just 3

I use a Tokina 400mm lens that hasn't got a mount on it without any problems.

I don't think the force is all that high. If you can pick the lens up by the K mount using just your forefinger and thumb with the lens horizontal there can't be much force. If the lens gets bashed against something.... that's a different story.

I guess those morons never bothered to look at what the screws were screwed into, because if they had looked the answer would have really screwed with thier little minds..


link
that is right, for most cameras, little tiny screws screwed into PLASTIC.... hence the reason I never cared that the new 35 2.4 is a plastic mount... it is at least as strong as the plastic the metal lens mount is screwed into...lol!
Fired many shots. Didn't kill anything.
Last Edited by Don on 24/04/2011 - 22:31

Smeggypants

Link Posted 24/04/2011 - 22:44
Mustn't forget the screws holding the lense's mount to the lens. Some of those don't look sturdy enough
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Add a Comment
You must be registered or logged-in to comment.