bleyton Loc: Los Angeles, CA

I'm just getting started with my new Sony A6000, and I am trying to understand the relationships between my various lenses and how they work on a crop sensor camera like mine.

I have a few old Minolta and Vivitar lenses from my film days. I bought a cheap adapter on eBay and have been playing around. I am trying to understand how the apertures and focal lengths work on an adapted full-frame lens.

My Sony lenses are the 16-50 and the 55-210 kit lenses. When I compare these to my film lenses, I know that I need to apply the crop factor, which means that my lenses will work more or less like a 24-75 and an 83-315 would on a film or full-frame camera. Is this also true of the apertures? Is a 3.5 max aperture really more like 5.25?

I guess the idea here is to understand what the advantages would be of using say, my 50mm 1.7 Minolta lens. Are the apertures on my old film lenses comparable to the stated ones on my modern Sony lenses (such that the 1.7 on my Minolta can be compared to the max available at 50mm on my Sony of 5.6)?

Interestingly enough, I took some pics at 50mm with the Sony 16-50, and then shot the same scene with the Minolta, at varying apertures. The Minolta at 1.7 was very smeary looking, but as I worked my way to smaller apertures, it got better. I'm not at all sure though that I see the great advantage of using the 50mm manual lens vs. having the zoom and autofocus of the Sony lens. The sharpness was not really any better to my eye, though I imagine there might be specific cases where I could shoot at say 2.8 or 4, and get better background blurring.

Sorry if I am meandering here, but I guess the main question is whether both aperture and focal length are comparable when looking at full-frame or adapted film lenses vs. a lens made for a crop sensor camera. Oh - and does the adapter figure in at all here? Do I lose anything when adapting a lens? I guess I am just trying to figure out whether it's even worthwhile to use my old lenses.

Brian

JPL

The aperture and focal length on your old glass is just the same as on your kit lenses. You do not need to use any multiplication or crop factors when comparing this old glass with the new one. You will understand this if you f.x. take a shot with your kit lens at 50 mm and then with your old Minolta 50 mm lens. You should have almost exactly the same picture in the frame in both shots given that you point your camera in the same direction and from the same spot in both cases.

Have you tried to use focus magnifier when shooting with your old Minolta lens on your camera?

bleyton Loc: Los Angeles, CA

Yes, I set Focus Magnifier to C1 to make it more accessible. I also like the way focus assist works, which makes it pretty easy to focus manually.

repleo Loc: Boston

The aperture is the aperture, it doesn't change regardless if it is a FF or an APS-C lens or if it is on a FF or crop sensor camera. Comparing depth of field for aps-c vs FF lenses gets much more complicated and can depend on whether you are shooting from the same distance or are zooming with your feet to get the same FoV.
The main thing you are loosing with adapted legacy lenses is auto focus and exif data. Manual focus is very easy with the A6000, but it just isin't going to be in the same league as a native Sony lens for speed. If you take portraits, make sure to set your camera up for 'eye focus'. This feature can detect an eye on a face and fine focus on that. It is not easy to set up, but it is worth it. I believe it only works with Sony lenses. Doesn't work with Sigma or other 3rd party lenses.
Also, many of the old legacy film lenses just aren't up to the quality of the native Sony lenses - even the kit lenses. The Sony E lenses can't be beat for lightness and compactness.

bleyton Loc: Los Angeles, CA

I guess what I am really looking for is a cheap way to get something faster than the kit lenses, without sacrificing (much) image quality. I am willing to deal with manual focusing and aperture priority mode to get this.

It sounds like there may be a place for the old lenses, but they aren't really a substitute for a good modern lens.

Case in point - I put my old 75-205 Vivitar together with a 2x teleconverter on the Sony and took some shots of the moon last night. I was rather impressed with the results, as compared with the kit telephoto. The longer reach really helped, and the sharpness was still quite decent. When cropped to similar size, the shots taken with the Vivitar were better to my eye.

At least I have a variety of combinations to play with. It will be fun figuring out the niche that each combination fits into.

repleo Loc: Boston

Using legacy glass makes sense for telephoto range on the A6000. Sony options for long e-mount lenses is bit thin and they are expensive.

47greyfox Loc: on the edge of the Colorado front range

It’s not simple. Although the actual is what it is, there is an effective delta relative to a full frame sensor both in focal length and aperture.
https://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-crop-factor

a6k Loc: Detroit & Sanibel

I have an alpha 6000 and got it originally with the same two kit lenses. I got rid of the 55-210 fairly early and got the excellent+ 70-200 G (F 4). I have tried Nikkor 200, Nikkor 300, Nikkor 28-85 and Nikkor 50 F 1.8. Only that last one gives me good results. I have also used an old Spiratone 300 mm mirror lens and a Sigma 600/8 mirror lens. I even have a 1.4 Nikon telextender.

There are some issues I have found troublesome.

1. the viewfinder is dark if you stop down. My Metabones adapter does not communicate with the camera at all. I don't know if there are better lenses for the purpose that can be used with a smarter adapter. I have to shoot either fully manual or aperture priority because the camera cannot control the aperture.

2. manually focusing means either using the "focus peaking" or turning that off and trying to see what is sharp. There is nothing comparable to the focusing screens on the old film SLRs. I have never managed to get reliable sharp focus this way. Perhaps others are better at it but that's a skill issue. I used to be, I thought, pretty good when it was a FM2 I was using. Maybe I just got old and sloppy. Dunno.

3. for reasons I never figured out, the Nikkor 200 and 300 primes would sometimes have significant red fringing. But only sometimes. I have not seen this with the 28-85 nor the 50.

As for effective focal length (angle of view), the 1.5 multiplier is at least approximately correct. At near distances there are differences when comparing zooms to primes. I have found that the image size does not always conform to the 1.5 specification even though the sensor size is correctly stated. It's close enough, though.

As for effective aperture, this is or can be as confusing as focal length. The actual focal length and the actual aperture are what they say they are (plus or minus the precision of the specification). So, for example, a 50 mm F 2.0 lens has an aperture of 25 mm by definition . Now put that lens on my a6000 and only some of the image is captured and the rest is CROPPED. That gives the narrower angle of view which we describe in terms of the same angle on a "full frame" camera. So some "experts" will tell you that this example will give you F 3.0 on a 1.5 crop sensor (75/25=3). This is an error because the lens is not 75 mm in reality.

For purposes of calculating exposure, the sunny 16 rule still works as do its derivatives. Some would have you believe that you should consider it a smaller aperture because the lens is longer. In my view, that is a serious error based on equating equivalences. You can easily confirm for yourself that the exposure is correct based on the real aperture and the real shutter speed. The camera's internal light metering will work correctly in my experience. You can immediately review the settings the camera used in "review" mode or just look at the EXIF. Sony's EXIF gives the brightness value. It will be wrong for legacy lenses but you can put on a Sony lens first to get the real value. That and some math will prove my assertion.

I hope this helps and is not TMI. There are a few of us with the same exact camera and comparable legacy lenses and I am among those willing to help and share data.

Soul Dr. Loc: Beautiful Shenandoah Valley

Sony makes adapters to use your Minolta AF lenses on the A6000. Will allow the lens to AF and communicate with the camera.
I have one for my A6000, as I have quite a bit of Minolta AF lenses.

Reinaldokool Loc: San Rafael, CA

Brian, if you will quit letting the marketing departments invade your camera, you will have the answers to some of your questions. There is no such thing as a "crop" sensor. The aps-c has a certain size. A 100mm lens used on the aps-c will always cover a certain area. If you want to cover the area that used to be 35mm film, you will need a lens that covers the larger area, that's all. There certainly is no difference in aperture, and f2.8 is f2.8 on either camera. f11 is f11. 100mm is 100mm.

I'm not saying that 35mm sensors don't have an advantage in certain situations. But the aps-c has some advantages too.

At best, the terms "full frame" and "crop" sensor made sense when they were trying to sell us old 35mm film folk on the new cameras. In the process they have caused more confusion and misinformation than they cleared up.

When the D850 and the new Sony come down in price a little, they will have sufficient improvement to be worth noting. Perhaps they will be worthy of the name "full frame" until Fuji decides to market a 6x7cm sensor with 150 megapixels.

bleyton Loc: Los Angeles, CA

Thank you a6k & Reinaldokool. I do appreciate the information, and no, it's not TMI.

I guess the thing that's bothering me is that when I was doing my research, there was a lot of information on how an APS-C sensor will give you a zoom or crop effect, such that a lens that was normal on my Minolta is now a mild telephoto on the Sony. No problem there, as I knew what I was going to get. Where I guess I am disappointed is that it seems that I am also paying a penalty in terms of exposure. I know people always talk about how full-frame sensors are better for low light, but what I assumed was that the main reason was lower noise given that the pixels are more spread out on a full-frame (assuming the same number of pixels overall). What I did not understand previously is that there is simply less light hitting my sensor than a full-frame. Therefore, all other things being equal, I will need a wider aperture or longer exposure to capture the same image as a full-frame.

Obviously I will just learn to deal with it, but it does seem as though some things that would be practical to shoot with a full-frame will not be possible with an APS-C sensor. After watching an excellent video course on Lynda.com about low-light photography, I was all ready to go out & shoot street scenes at night. I still plan to do that, but I may need to adjust my expectations somewhat.

Brian

a6k Loc: Detroit & Sanibel

Respectfully, Brian, I think you have got it wrong about exposure. Here is an alternate explanation.

Let's take a 100 mm prime, F 4.0 lens (these are physical specifications) and put it on a full frame camera when the conditions are correct for "sunny 16" but let's use F 8.0 and two stops faster shutter than the reciprocal of the ISO. For maximum image quality let's use ISO 100 so the shutter is set at 400. This is an approximately correct exposure in those conditions.

Now put that lens on an a6000, use the same aperture, ISO and shutter. Your results will be, within a tolerable range, just as correct. That is because the lens is trying to take the outdoor brightness, applied against the same 12.5 mm circle (100/8=12.5) as before. The brightness hitting the sensor is the same as on the full frame camera. You are merely choosing to use a smaller, central portion of the image that the lens forms. The amount of light hitting an equal area of the sensor is equal; the difference is that the smaller sensor will receive less total light. Exposure is about the intensity of the light times the duration where the intensity is a function of brightness and actual aperture.

If you took 1/4 of the area of the full frame sensor you would be using 1/4 of the light (think photons) but the exposure values (time, aperture, ISO) should be the same.

There is a difference in low light performance with the crop sensor cameras but the reason is the same as why the a7R series is not as good in low light as the a7S series or the a9. The size and design of the sensor and its pixels are the culprits.

Your a6000 will be just as light sensitive, using the same lens, as if it were on a full frame camera. But the a6000 is not as good as the full frame in low light, regardless of lens. The same issue happens when you compare, for example, my 1" sensor RX10m3 to my a6000. The low light performance of the a6000 is superior. But that simply means the sensor handles higher ISO settings better and has nothing to do with the crop factor. The same effect is easily observed comparing the bridge cameras having the so called 1/2.3 sensors to the 1" nominal sensors which are twice as big and have 4X the area.

Tiny pixels simply do not gather as much light at a given level of brightness because they are smaller and there are also cost-based issues with the construction of the sensor. If you look at the size of the pixels or its reciprocal, the pixels-per-square_mm then you may see what I'm trying to explain.

bleyton Loc: Los Angeles, CA

So a6k, it sounds like you are telling me that my original assumption is in fact correct - that the main difference between an APS-C and 35mm sensor is mainly due to the sensor itself.

Well, that's a relief!

I guess I am just trying to understand how my new camera compares with what I am used to from my film days. It's good to know that 1.7 is still 1.7 when I am using my 50mm Minolta lens, though the resolution of the Sony is so much better than film that I am now seeing the limitations of the old lenses better than ever before.

I suppose that what I really need is to get out there with the camera and see for myself how all of this theory translates in the real world.

Thanks for the great explanation - no need to tiptoe around when pointing out my errors. I am still trying to get my head around all of these concepts, and there is a lot to learn.